Search results for: photoelectron spectroscopy

Authors: B. Kurbanova, M. Karibayev, N. Almas, K. Ospanov, K. Aimaganbetov, T. Kuanyshbekov, K. Akatan, S. Kabdrakhmanova

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Proton exchange membranes (PEMs) operating at high temperatures above 100 °C with the excellent mechanical, chemical and thermochemical stability have been received much attention, because of their practical application of proton exchange membrane fuel cells (PEMFCs). Nowadays, a huge number of polymers and polymer-mixed various membranes have been investigated for this application, all of which offer both pros and cons. However, PEMFCs are still lack of ideal membranes with unique properties. In this work, carboxymethylcellulose (CMC) based membranes with dispersive graphene oxide (GO) sheets were fabricated and investigated for PEMFCs application. These membranes and pristine GO were studied by a combination of XRD, XPS, Raman, Brillouin, FTIR, thermo-mechanical analysis (TGA and Dynamic Mechanical Analysis) and SEM microscopy, while substantial studies on the proton transport properties were provided by Electrochemical Impedance Spectroscopy (EIS) measurements. It was revealed that the addition of CMC to the GO boosts proton conductivity of the whole membrane, while GO provides good mechanical and thermomechanical stability to the membrane. Further, the continuous and ordered nanochannels with well-tailored chemical structures were obtained by irradiation of heavy ions Kr⁺¹⁷ with an energy of 1.75 MeV/nucleon on the heavy ion accelerator. The formation of these nanochannels led to the significant increase of proton conductivity at 50% Relative Humidity. Also, FTIR and XPS measurement results show that ion irradiation eliminated the GO’s surface oxygen chemical bonds (C=O, C-O), and led to the formation of C = C, C – C bonds, whereas these changes connected with an increase in conductivity.

Keywords: proton exchange membranes, graphene oxide, fuel cells, carboxymethylcellulose, ion irradiation

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Authors: Francisco Pedroza-Montero, Jesús Naín Pedroza-Montero, Diego Soto-Puebla, Osiris Alvarez-Bajo, Beatriz Castaneda, Sofía Navarro-Espinoza, Martín Pedroza-Montero

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Nanodiamonds have been widely studied for their physical properties, including chemical inertness, biocompatibility, optical transparency from the ultraviolet to the infrared region, high thermal conductivity, and mechanical strength. In this work, we studied how the fluorescence spectrum of nanodiamonds quenches concerning the concentration in aqueous solutions systematically ranging from 0.1 to 10 mg/mL. Our results demonstrated a non-linear fluorescence quenching as the concentration increases for both of the NV zero-phonon lines; the 5 mg/mL concentration shows the maximum fluorescence emission. Furthermore, this behaviour is theoretically explained as an electronic recombination process that modulates the intensity in the NV centres. Finally, to gain more insight, the FRET methodology is used to determine the fluorescence efficiency in terms of the fluorophores' separation distance. Thus, the concentration level is simulated as follows, a small distance between nanodiamonds would be considered a highly concentrated system, whereas a large distance would mean a low concentrated one. Although the 5 mg/mL concentration shows the maximum intensity, our main interest is focused on the concentration of 0.5 mg/mL, which our studies demonstrate the optimal human cell viability (99%). In this respect, this concentration has the feature of being as biocompatible as water giving the possibility to internalize it in cells without harming the living media. To this end, not only can we track nanodiamonds on the surface or inside the cell with excellent precision due to their fluorescent intensity, but also, we can perform thermometry tests transforming a fluorescence contrast image into a temperature contrast image.

Keywords: nanodiamonds, fluorescence spectroscopy, concentration, bioimaging, thermometry

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Authors: Arturo Reyes Roman, Daniza Castillo Godoy, Francisca Balarezo Olivares, Francisco Arriagada Castro, Miguel Maulen Tapia

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Mining waste–based geopolymers are a sustainable alternative to conventional cement materials due to their contribution to the valorization of mining wastes as well as to the new construction materials with reduced fingerprints. The objective of this study was to determine the potential of leaching gravel (LG) from hydrometallurgical copper processing to be used as a raw material in the manufacture of geopolymer. NaOH, Na2SiO3 (modulus 1.5), and LG were mixed and then wetted with an appropriate amount of tap water, then stirred until a homogenous paste was obtained. A liquid/solid ratio of 0.3 was used for preparing mixtures. The paste was then cast in cubic moulds of 50 mm for the determination of compressive strengths. The samples were left to dry for 24h at room temperature, then unmoulded before analysis after 28 days of curing time. The compressive test was conducted in a compression machine (15/300 kN). According to the laser diffraction spectroscopy (LDS) analysis, 90% of LG particles were below 500 μm. The X-ray diffraction (XRD) analysis identified crystalline phases of albite (30 %), Quartz (16%), Anorthite (16 %), and Phillipsite (14%). The X-ray fluorescence (XRF) determinations showed mainly 55% of SiO2, 13 % of Al2O3, and 9% of CaO. ICP (OES) concentrations of Fe, Ca, Cu, Al, As, V, Zn, Mo, and Ni were 49.545; 24.735; 6.172; 14.152, 239,5; 129,6; 41,1;15,1, and 13,1 mg kg-1, respectively. The geopolymer samples showed resistance ranging between 2 and 10 MPa. In comparison with the raw material composition, the amorphous percentage of materials in the geopolymer was 35 %, whereas the crystalline percentage of main mineral phases decreased. Further studies are needed to find the optimal combinations of materials to produce a more resistant and environmentally safe geopolymer. Particularly are necessary compressive resistance higher than 15 MPa are necessary to be used as construction unit such as bricks.

Keywords: mining waste, geopolymer, construction material, alkaline activation

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Authors: David Ryan, Martin Breugst, Turlough Downes, Peter A. Byrne, Gerard P. McGlacken

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An ambident nucleophile is a nucleophile that possesses two or more distinct nucleophilic sites that are linked through resonance and are effectively “in competition” for reaction with an electrophile. Examples include enolates, pyridone anions, and nitrite anions, among many others. Reactions of ambident nucleophiles and electrophiles are extremely prevalent at all levels of organic synthesis. The principle of hard and soft acids and bases (the “HSAB principle”) is most commonly cited in the explanation of selectivities in such reactions. Although this rationale is pervasive in any discussion on ambident reactivity, the HSAB principle has received considerable criticism. As a result, the principle’s supplantation has become an area of active interest in recent years. This project focuses on developing a model for rationalizing ambident reactivity. Presented here is an approach that incorporates computational calculations and experimental kinetic data to construct Gibbs energy profile diagrams. The preferred site of alkylation of nitrite anion with a range of ‘hard’ and ‘soft’ alkylating agents was established by ¹H NMR spectroscopy. Pseudo-first-order rate constants were measured directly by ¹H NMR reaction monitoring, and the corresponding second-order constants and Gibbs energies of activation were derived. These, in combination with computationally derived standard Gibbs energies of reaction, were sufficient to construct Gibbs energy wells. By representing the ambident system as a series of overlapping Gibbs energy wells, a more intuitive picture of ambident reactivity emerges. Here, previously unexplained switches in reactivity in reactions involving closely related electrophiles are elucidated.

Keywords: ambident, Gibbs, nucleophile, rates

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Authors: Hanane Belayachi, Sarra Bourahla, Amel Belayachi, Fadela Nemchi, Mostefa Belhakem

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The most used techniques to remove pollutants from wastewater are adsorption onto activated carbon (AC) and oxidation using a photocatalyst slurry. The aim of this work is to eliminate such drawbacks by combining AC and titanium dioxide (TiO₂) in a photocatalytically Regenerative Activated Carbon. Anatase titania was deposited on powder-activated carbon made from grape seeds by the impregnation method, and then the composite photocatalyst was employed for the removal of reactive black 5, which is an anionic azo dye, from water. The AGS/TiO₂ was characterized by BET, MEB, RDX and optical absorption spectroscopy. The BET surface area and the pore structure of composite photocatalysts (AGS/TiO₂) and activated grape seeds (AGS) were evaluated from nitrogen adsorption data at 77 K in relation to process conditions. Our results indicate that the photocatalytic activity of AGS/TiO₂ was much higher than single-phase titania. The adsorption equilibrium of reactive black 5 from aqueous solutions on the examined materials was investigated. Langmuir, Freundlich, and Redlich–Petersen models were fitted to experimental equilibrium data, and their goodness of fit is compared. The degradation kinetics fitted well to the Langmuir-Hinselwood pseudo first order rate low. The photocatalytic activity of AGS/TiO₂ was much higher than virgin TiO₂. Chemical oxygen demand (COD) removal was measured at regular intervals to quantify the mineralization of the dye. Above 96% mineralization was observed. These results suggest that UV-irradiated TiO₂ immobilized on activated carbon may be considered an adequate process for the treatment of diluted colored textile wastewater.

Keywords: activated carbon, pollutant, catalysis, TiO₂

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Authors: Manasa Perikala, Asha Bhardwaj

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Fluorescent carbon dots (CDs), a young member of Carbon nanomaterial family, has gained a lot of research attention across the globe due to its highly luminescent emission properties, non-toxic behavior, stable emission properties, and zero re-absorption lose. These dots have the potential to replace the use of traditional semiconductor quantum dots in light-emitting devices (LED’s, fiber lasers) and other photonic devices (temperature sensor, UV detector). However, One major drawback of Carbon dots is that, till date, the actual mechanism of photoluminescence (PL) in carbon dots is still an open topic of discussion among various researchers across the globe. PL mechanism of CDs based on wide particle size distribution, the effect of surface groups, hybridization in carbon, and charge transfer mechanisms have been proposed. Although these mechanisms explain PL of CDs to an extent, no universally accepted mechanism to explain complete PL behavior of these dots is put forth. In our work, we report parameters affecting the size and surface of CDs, such as time of the reaction, synthesis temperature and concentration of precursors and their effects on the optical properties of the carbon dots. The effect of auxochromes on the emission properties and re-modification of carbon surface using an external surface functionalizing agent is discussed in detail. All the explanations have been supported by UV-Visible absorption, emission spectroscopies, Fourier transform infrared spectroscopy and Transmission electron microscopy and X-Ray diffraction techniques. Once the origin of PL in CDs is understood, parameters affecting PL centers can be modified to tailor the optical properties of these dots, which can enhance their applications in the fabrication of LED’s and other photonic devices out of these carbon dots.

Keywords: carbon dots, photoluminescence, size effects on emission in CDs, surface modification of carbon dots

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Authors: Vineeta Kaushik, Manisha Goel

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Chaperones are proteins that help other proteins fold correctly, and are found in all domains of life i.e., prokaryotes, eukaryotes and archaea. Various comparative genomic studies have suggested that the archaeal protein folding machinery appears to be highly similar to that found in eukaryotes. In case of protein folding; slow rotation of peptide prolyl-imide bond is often the rate limiting step. Formation of the prolyl-imide bond during the folding of a protein requires the assistance of other proteins, termed as peptide prolyl cis-trans isomerases (PPIases). Cyclophilins constitute the class of peptide prolyl isomerases with a wide range of biological function like protein folding, signaling and chaperoning. Most of the cyclophilins exhibit PPIase enzymatic activity and play active role in substrate protein folding which classifies them as a category of molecular chaperones. Till date, there is not very much data available in the literature on archaeal cyclophilins. We aim to compare the structural and biochemical features of the cyclophilin protein from within the three domains to elucidate the features affecting their stability and enzyme activity. In the present study, we carry out in-silico analysis of the cyclophilin proteins to predict their conserved residues, sites under positive selection and compare these proteins to their bacterial and eukaryotic counterparts to predict functional divergence. We also aim to clone and express these proteins in heterologous system and study their biophysical characteristics in detail using techniques like CD and fluorescence spectroscopy. Overall we aim to understand the features contributing to the folding, stability and dynamics of the archaeal cyclophilin proteins.

Keywords: biophysical characterization, x-ray crystallography, chaperone-like activity, cyclophilin, PPIase activity

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Authors: Ghulam Mustafa Kamal, Xiaohua Wang, Bin Yuan, Abdullah Ijaz Hussain, Jie Wang, Shahzad Ali Shahid Chatha, Xu Zhang, Maili Liu

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Organic food products are becoming increasingly popular in recent years, as consumers have turned more health conscious and environmentally aware. A lot of consumers have understood that the organic foods are healthier than conventionally produced food stuffs. Price difference between conventional and organic foods is very high. So, it is very common to cheat the consumers by mislabeling and adulteration. Our study describes the 1H NMR based approach to characterize and differentiate soy sauce prepared from organically and conventionally grown raw materials (wheat and soybean). Commercial soy sauce samples fermented from organic and conventional raw materials were purchased from local markets. Principal component analysis showed clear separation among organic and conventional soy sauce samples. Orthogonal partial least squares discriminant analysis showed a significant (p < 0.01) separation among two types of soy sauce yielding leucine, isoleucine, ethanol, glutamate, lactate, acetate, β-glucose, sucrose, choline, valine, phenylalanine and tyrosine as important metabolites contributing towards this separation. Abundance ratio of 13C to 12C was also evaluated by 1H NMR spectroscopy which showed an increased ratio of 13C isotope in organic soy sauce samples indicating the organically grown wheat and soybean used for the preparation of organic soy sauce. Results of the study can be helpful to the end users to select the soy sauce of their choice. This information could also pave the way to further trace and authenticate the raw materials used in production of soy sauce.

Keywords: 1H NMR, multivariate analysis, organic, conventional, 13C isotopic ratio, soy sauce

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Authors: Karima Benfadel, Lamia Talbi, Sabiha Anas Boussaa, Afaf Brik, Assia Boukezzata, Yahia Ouadah, Samira Kaci

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In order to prevent global warming, which is mainly caused by the increase in carbon dioxide levels in the atmosphere, it is interesting to produce renewable energy in the form of chemical energy by converting carbon dioxide into alternative fuels and other energy-dense products. Photoelectrochemical reduction of carbon dioxide to value-added products and fuels is a promising and current method. The objective of our study is to develop Cu₂S-based photoélectrodes, in which Cu₂S is used as a CO₂ photoelectrocatalyst deposited on nanostructured silicon substrates. Cu₂S thin layers were deposited using the chemical bath deposition (CBD) technique. Silicon nanowires and nanopyramids were obtained by alkaline etching. SEM and UV-visible spectroscopy was used to analyse the morphology and optical characteristics. By using a potentiostat station, we characterized the photoelectrochemical properties. We performed cyclic voltammetry in the presence and without CO₂ purging as well as linear voltammetry (LSV) in the dark and under white light irradiation. We perform chronoamperometry to study the stability of our photocathodes. The quality of the nanowires and nanopyramids was visible in the SEM images, and after Cu₂S deposition, we could see how the deposition was distributed over the textured surfaces. The inclusion of the Cu₂S layer applied on textured substrates significantly reduces the reflectance (R%). The catalytic performance towards CO₂ conversion of Cu₂S/Si-based photocathodes revealed that the texturing of the silicon surface with nanowires and pyramids has a better photoelectrochemical behavior than those without surface modifications.

Keywords: CO₂ conversion, Cu₂S photocathode, silicone nanostructured, electrochemistry

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Authors: Alexandre H. Okano, Pedro M. D. Agrícola, Daniel G. Da S. Machado, Luiz I. Do N. Neto, Luiz F. Farias Junior, Paulo H. D. Nascimento, Rickson C. Mesquita, John F. Araujo, Eduardo B. Fontes, Hassan M. Elsangedy, Shinsuke Shimojo, Li M. Li

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The prefrontal cortex is involved in the reward system and the insular cortex integrates the afferent inputs arriving from the body’ systems and turns into feelings. Therefore, modulating neuronal activity in these regions may change individuals’ perception in a given situation such as exercise. We tested whether transcranial direct current stimulation (tDCS) change cerebral oxygenation and pleasure during exercise. Fourteen volunteer healthy adult men were assessed into five different sessions. First, subjects underwent to a maximum incremental test on a cycle ergometer. Then, subjects were randomly assigned to a transcranial direct current stimulation (2mA for 15 min) intervention in a cross over design in four different conditions: anode and cathode electrodes on T3 and Fp2 targeting the insular cortex, and Fpz and F4 targeting prefrontal cortex, respectively; and their respective sham. These sessions were followed by 30 min of moderate intensity exercise. Brain oxygenation was measured in prefrontal cortex with a near infrared spectroscopy. Perceived exertion and pleasure were also measured during exercise. The asymmetry in prefrontal cortex oxygenation before the stimulation decreased only when it was applied over this region which did not occur after insular cortex or sham stimulation. Furthermore, pleasure was maintained during exercise only after prefrontal cortex stimulation (P > 0.7), while there was a decrease throughout exercise (P < 0.03) during the other conditions. We conclude that tDCS over the prefrontal cortex changes brain oxygenation in ventromedial prefrontal cortex and maintains perceived pleasure during exercise. Therefore, this technique might be used to enhance effective responses related to exercise.

Keywords: affect, brain stimulation, dopamine neuromodulation, pleasure, reward, transcranial direct current stimulation

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Authors: Angelo Gabriel Buenaventura, Allan Christopher Yago

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A carbon paste electrode (CPE) composed of Multiwalled Carbon Nanotube (MWCNT) conducting particle and Polydimethylsiloxane (PDMS) binder was used for simultaneous detection of Dopamine (DA) and Uric Acid (UA) in the presence of Ascorbic Acid (AA) at physiological level. The MWCNT-PDMS CPE was initially activated via potentiodynamic cycling in a basic (NaOH) solution, which resulted in enhanced electrochemical properties. Electrochemical Impedance Spectroscopy measurements revealed a significantly lower charge transfer resistance (Rct) for the OH--activated MWCNT-PDMS CPE (Rct = 5.08kΩ) as compared to buffer (pH 7)-activated MWCNT-PDMS CPE (Rct = 25.9kΩ). Reversibility analysis of Fe(CN)63-/4- redox couple of both Buffer-Activated CPE and OH--Activated CPE showed that the OH—Activated CPE have peak current ratio (Ia/Ic) of 1.11 at 100mV/s while 2.12 for the Buffer-Activated CPE; this showed an electrochemically reversible behavior for Fe(CN)63-/4- redox couple even at relatively fast scan rate using the OH--activated CPE. Enhanced voltammetric signal for DA and significant peak separation between DA and UA was obtained using the OH--activated MWCNT-PDMS CPE in the presence of 50 μM AA via Differential Pulse Voltammetry technique. The anodic peak currents which appeared at 0.263V and 0.414 V were linearly increasing with increasing concentrations of DA and UA, respectively. The linear ranges were obtained at 25 μM – 100 μM for both DA and UA. The detection limit was determined to be 3.86 μM for DA and 5.61 μM for UA. These results indicate a practical approach in the simultaneous detection of important bio-organic molecules using a simple CPE composed of MWCNT and PDMS with base anodization as activation technique.

Keywords: anodization, ascorbic acid, carbon paste electrodes, dopamine, uric acid

Procedia PDF Downloads 287

Authors: I. D. Laryushin, V. A. Kostin, A. A. Silaev, N. V. Vvedenskii

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Generation of broadband intense terahertz (THz) radiation attracts reasonable interest due to various applications, such as the THz time-domain spectroscopy, the probing and control of various ultrafast processes, the THz imaging with subwavelength resolution, and many others. One of the most promising methods for generating powerful and broadband terahertz pulses is based on focusing two-color femtosecond ionizing laser pulses in gases, including ambient air. For this method, the amplitudes of terahertz pulses are determined by the free-electron current density remaining in a formed plasma after the passage of the laser pulse. The excitation of this residual current density can be treated as multi-wave mixing: Аn effective generation of terahertz radiation is possible only when the frequency ratio of one-color components in the two-color pulse is close to irreducible rational fraction a/b with small odd sum a + b. This work focuses on the optimal parameters (polarizations and intensities) of laser components for the strongest THz generation. The optimal values of parameters are found numerically and analytically with the use of semiclassical approach for calculating the residual current density. For frequency ratios close to a/(a ± 1) with natural a, the strongest THz generation is shown to take place when the both laser components have circular polarizations and equal intensities. For this optimal case, an analytical formula for the residual current density was derived. For the frequency ratios such as 2/5, the two-color ionizing pulses with circularly polarized components practically do not excite the residual current density. However, the optimal parameters correspond generally to specific elliptical (not linear) polarizations of the components and intensity ratios close to unity.

Keywords: broadband terahertz radiation, ionization, laser plasma, ultrashort two-color pulses

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Authors: M. Tabatabaee, R. Mohebat, M. Baranian

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Textile industries produce large volumes of colored dye effluents which are toxic and non-biodegradable. Earlier studies have shown that a wide range of organic substrates can be completely photo mineralized in the presence of photocatalysts and oxidant agents. ZnO and TiO2 are important photocatalysts with high catalytic activity that have attracted much research attention. Zinc sulfide is one of the semiconductor nanomaterials that can be used for the production of optical sensitizers, photocatalysts, electroluminescent materials, optical sensors and for solar energy conversion. The synthesis of ZnS nanoparticles has been tried by various methods and sulfide sources. Elementary sulfur powder, H2S or Na2S are used as sulfide sources for synthesis of ZnS nano particles. Recently, solar energy is has been successfully used for photocatalytic degradation of dye pollutant. Studies have shown that the use of metal oxides or sulfides with ZnO or TiO2 can significantly enhance the photocatalytic activity of them. In this research, Nano-sized zinc sulfide was synthesized successfully by a simple method using thioasetamide as sulfide source in the presence of polyethylene glycol (PEG 2000). X-ray diffraction (XRD) spectroscopy scanning electron microscope (SEM) was used to characterize the structure and morphology synthesized powder. The effect of photocatalytic activity of prepared ZnS and ZnS/ZnO, on degradation of direct Black19 under UV and sunlight irradiation was investigated. The effects of various parameters such as amount of photocatalyst, pH, initial dye concentration and irradiation time on decolorization rate were systematically investigated. Results show that more than 80% of 500 mgL-1 of dye decolorized in 60-min reaction time under UV and solar irradiation in the presence of ZnS nanoparticles. Whereas, mixed ZnS/ZnO (50%) can decolorize more than 80% of dye in the same conditions.

Keywords: zinc sulfide, nano articles, photodegradation, solar light

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Authors: Carolina V. Viegas, Monique Gonçalves, Gisel Chenard Diaz, Yordanka Reyes Cruz, Donato Alexandre Gomes Aranda

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To develop the massive cultivation of microalgae, it is necessary to isolate and characterize the species, improving genetic tools in search of specific characteristics. Therefore, the detection, identification and quantification of the compounds that compose the Scenedesmus sp. were prerequisites to verify the potential of these microalgae. The main objective of this work was to carry out the characterization of Scenedesmus sp. as to the content of ash, carbohydrates, proteins and lipids as well as the determination of the composition of their lipid classes and main fatty acids. The biomass of Scenedesmus sp, showed 15,29 ± 0,23 % of ash and CaO (36,17 %) was the main component of this fraction, The total protein and carbohydrate content of the biomass was 40,74 ± 1,01 % and 23,37 ± 0,95 %, respectively, proving to be a potential source of proteins as well as carbohydrates for the production of ethanol via fermentation, The lipid contents extracted via Bligh & Dyer and in situ saponification were 8,18 ± 0,13 % and 4,11 ± 0,11 %, respectively. In the lipid extracts obtained via Bligh & Dyer, approximately 50 % of the composition of this fraction consists of fatty compounds, while the other half is composed of an unsaponifiable fraction composed mainly of chlorophylls, phytosterols and carotenes. From the lowest yield, it was possible to obtain a selectivity of 92,14 % for fatty components (fatty acids and fatty esters) confirmed through the infrared spectroscopy technique. The presence of polyunsaturated acids (~45 %) in the lipid extracts indicated the potential of this fraction as a source of nutraceuticals. The results indicate that the biomass of Scenedesmus sp, can become a promising potential source for obtaining polyunsaturated fatty acids, carotenoids and proteins as well as the simultaneous obtainment of different compounds of high commercial value.

Keywords: microalgae, Desmodesmus, lipid classes, fatty acid profile, proteins, carbohydrates

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Authors: Abhimanyu Thakur, Youngjin Lee

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Glioma is a lethal brain cancer whose early diagnosis and prognosis are limited due to the dearth of a suitable technique for its early detection. Current approaches, including magnetic resonance imaging (MRI), computed tomography (CT), and invasive biopsy for the diagnosis of this lethal disease, hold several limitations, demanding an alternative method. Recently, extracellular vesicles (EVs) have been used in numerous biomarker studies, majorly exosomes and microvesicles (MVs), which are found in most of the cells and biofluids, including blood, cerebrospinal fluid (CSF), and urine. Remarkably, glioma cells (GMs) release a high number of EVs, which are found to cross the blood-brain-barrier (BBB) and impersonate the constituents of parent GMs including protein, and lncRNA; however, biophysical properties of EVs have not been explored yet as a biomarker for glioma. We isolated EVs from cell culture conditioned medium of GMs and regular primary culture, blood, and urine of wild-type (WT)- and glioma mouse models, and characterized by nano tracking analyzer, transmission electron microscopy, immunogold-EM, and differential light scanning. Next, we measured the biophysical parameters of GMs-EVs by using atomic force microscopy. Further, the functional constituents of EVs were examined by FTIR and Raman spectroscopy. Exosomes and MVs-derived from GMs, blood, and urine showed distinction biophysical parameters (roughness, adhesion force, and stiffness) and different from that of regular primary glial cells, WT-blood, and -urine, which can be attributed to the characteristic functional constituents. Therefore, biophysical features can be potential diagnostic biomarkers for glioma.

Keywords: glioma, extracellular vesicles, exosomes, microvesicles, biophysical properties

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Authors: S. S. Sravanthi, Swati Ghosh Acharyya

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Automotive light weighting is of major prominence in the current times due to its contribution in improved fuel economy and reduced environmental pollution. Various arc welding technologies are being employed in the production of automobile components with reduced weight. The present study is of practical importance since it involves preferential substitution of Zinc coated mild steel with a light weight alloy such as 6061 Aluminium by means of Gas Metal Arc Welding (GMAW) – Brazing technique at different processing parameters. However, the fabricated joints have shown the generation of Al – Fe layer at the interfacial regions which was confirmed by the Scanning Electron Microscope and Energy Dispersion Spectroscopy. These Al-Fe compounds not only affect the mechanical strength, but also predominantly deteriorate the corrosion resistance of the joints. Hence, it is essential to understand the phases formed in this layer and their crystal structure. Micro area X - ray diffraction technique has been exclusively used for this study. Moreover, the crevice corrosion analysis at the joint interfaces was done by exposing the joints to 5 wt.% FeCl₃ solution at regular time intervals as per ASTM G 48-03. The joints have shown a decreased crevice corrosion resistance with increased heat intensity. Inner surfaces of welds have shown severe oxide cracking and a remarkable weight loss when exposed to concentrated FeCl₃. The weight loss was enhanced with decreased filler wire feed rate and increased heat intensity. 

Keywords: automobiles, welding, corrosion, lap joints, Micro XRD

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Authors: Imen Blibech, Mohiedine Ksantini, Mohamed Bouaziz

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Prays oleae is a major insect of olive in the Mediterranean Region. In an effort to find effective and affordable ways of controlling this pest, larvicidal activity of essential oils from Tunisian Thymus capitatus were analyzed in comparison to Azadirachtin, a biologically active compound insecticide. The essential oils were extracted by hydrodistillation, and their chemical composition was determined by gas liquid-chromatography coupled with mass spectroscopy. The main components of chemical components were oxygenated monoterpenes (60.24%). The most abundant oxygenated monoterpenes were carvacrol (54.11%). Monoterpenes hydrocarbons were much more abundant and dominated by the o-cymene (16.68%). Both active compounds of Azadirachtin and Thymus capitatus oil extracts exhibited significant larvicidal activity against P. oleae with LC50 values 81.30 ppm and 52.49 ppm respectively. Dose-response relationships were established with almost 100% mortality when using the highest dose 100 ppm of T. capitatus oil extracts and 80 ppm of Azadirachtin. At the lowest dose (10 ppm), T. capitatus oil extracts and Azadirachtin caused 60% and 76% larval mortality in 48 hours respectively. The larval mortality rate greatly decreased with increases of the dilution of both oil extract compounds. Larval development duration appeared to be prolonged to about 12 days for larvae feeding on control diet. The maximum antifeedant activity was shown by both T. capitatus oil extract and Azadirachtin at LC90 values (47.5 and 50.1 ppm respectively). Tunisian T. capitatus oil extract used at low concentrations could be considered as eco-friendly promising insecticide similar to Azadirachtin that has significant potential for the biological control of P. oleae.

Keywords: Thymus capitatus, chemical composition, azadirachtin, larvicidal effects, antifeedant activity, Prays oleae

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Authors: Tatyana T. Tabakova, Elitsa N. Kolentsova, Dimitar Y. Dimitrov, Krasimir I. Ivanov, Yordanka G. Karakirova, Petya Cv. Petrova, Georgi V. Avdeev

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The catalytic oxidation of CO and volatile organic compounds (VOCs) is considered as one of the most efficient ways to reduce harmful emissions from various chemical industries. The effectiveness of gold-based catalysts for many reactions of environmental significance was proven during the past three decades. The aim of this work was to combine the favorable features of Au and Cu-Ce mixed oxides in the design of new catalytic materials of improved efficiency and economic viability for removal of air pollutants in waste gases from formaldehyde production. Supported oxides of copper and cerium with Cu: Ce molar ratio 2:1 and 1:5 were prepared by wet impregnation of g-alumina. Gold (2 wt.%) catalysts were synthesized by a deposition-precipitation method. Catalysts characterization was carried out by texture measurements, powder X-ray diffraction, temperature programmed reduction and electron paramagnetic resonance spectroscopy. The catalytic activity in the oxidation of CO, CH₃OH and (CH₃)₂O was measured using continuous flow equipment with fixed bed reactor. Both Cu-Ce/alumina samples demonstrated similar catalytic behavior. The addition of gold caused significant enhancement of CO and methanol oxidation activity (100 % degree of CO and CH₃OH conversion at about 60 and 140 ^oC, respectively). The composition of Cu-Ce mixed oxides affected the performance of gold-based samples considerably. Gold catalyst on Cu-Ce/γ-Al₂O₃ 1:5 exhibited higher activity for CO and CH₃OH oxidation in comparison with Au on Cu-Ce/γ-Al₂O₃ 2:1. The better performance of Au/Cu-Ce 1:5 was related to the availability of highly dispersed gold particles and copper oxide clusters in close contact with ceria.

Keywords: CO and VOCs oxidation, copper oxide, Ceria, gold catalysts

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Authors: F. Yılmaz, Y. Saylan, A. Derazshamshir, S. Atay, A. Denizli

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Quartz crystal microbalance (QCM), high-resolution mass-sensing technique, measures changes in mass on oscillating quartz crystal surface by measuring changes in oscillation frequency of crystal in real time. Protein adsorption techniques via hydrophobic interaction between protein and solid support, called hydrophobic interaction chromatography (HIC), can be favorable in many cases. Some nanoparticles can be effectively applied for HIC. HIC takes advantage of the hydrophobicity of proteins by promoting its separation on the basis of hydrophobic interactions between immobilized hydrophobic ligands and nonpolar regions on the surface of the proteins. Lysozyme is found in a variety of vertebrate cells and secretions, such as spleen, milk, tears, and egg white. Its common applications are as a cell-disrupting agent for extraction of bacterial intracellular products, as an antibacterial agent in ophthalmologic preparations, as a food additive in milk products and as a drug for treatment of ulcers and infections. Lysozyme has also been used in cancer chemotherapy. The aim of this study is the synthesis of hydrophobic nanoparticles for Lysozyme detection. For this purpose, methacryoyl-L-phenylalanine was chosen as a hydrophobic matrix. The hydrophobic nanoparticles were synthesized by micro-emulsion polymerization method. Then, hydrophobic QCM nanosensor was characterized by Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM) and zeta size analysis. Hydrophobic QCM nanosensor was tested for real-time detection of Lysozyme from aqueous solution. The kinetic and affinity studies were determined by using Lysozyme solutions with different concentrations. The responses related to a mass (Δm) and frequency (Δf) shifts were used to evaluate adsorption properties.

Keywords: nanosensor, HIC, lysozyme, QCM

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Authors: Mudawi M. Nour

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Background: Now a days, the multidisciplinary scientific research conception in the field of nanotechnology has witnessed development with regard to the numerous applications and synthesis of nanomaterials. Objective: The current investigation has been conducted with the main focus on the green synthesis of silver nanoparticles from the leaves of Salvadora persica and its antibacterial activity against MDR pathogens E. coli and S. aureus. Methodology: Silver nanoparticles (AgNPs) were prepared after addition of aqueous extract of Salvadora persica leaves. The UV-Vis spectrophotometer, Transmission Electron Microscopy (TEM), zeta potential and Scanning Electron Microscopy (SEM) were employed to detect the particle size and morphology, besides Fourier transform infra-red spectrometer (FTIR) analysis was performed to determine the capping and stabilizing agents in the extract. Antibacterial assay for the biogenic AgNPs was conducted against E. coli and S. aureus. Results: Color change of the mixture from yellow to dark brown is the first indication to AgNPs formation. Furthermore, 420 nm was the peak value for UV-Vis spectroscopy absorption of the mixture. Besides, TEM and SEM micrographs showed wide variability in the diameter of smaller NPs aggregated together with spherical shapes, and zeta sizer showed about 153.3 nm as an average size of nanoparticles. Microbial suppression was noticed for the tested microorganisms. Furthermore, with the help of FTIR analysis, the biomolecules that act as capping and stabilizing agents of AgNPs are proteins and phenols present in the plant extract. Conclusion: Salvadora persica leaves extract act as a reducing and stabilizing agent for the synthesis of AgNPs, keeping its ability to suppress the MDR pathogen.

Keywords: green synthesis, FTIR, MDR pathogen, salvadora persica

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Authors: Anoff Anim, Lila Mahmoud, Maria Katsikogianni, Sanjit Nayak

Abstract:

Sustained and controlled delivery of antimicrobial drugs have been largely studied recently using metal organic frameworks (MOFs)and different polymers. However, much attention has not been given to combining both MOFs and biodegradable polymers, which would be a good strategy in providing a sustained gradual release of the drugs. Herein, we report a comparative study of the sustained and controlled release of widely used antibacterial drugs, cephalexin and metronidazole, from zinc-based MOF-5 incorporated in biodegradable polycaprolactone (PCL) and poly-lactic glycolic acid (PLGA) membranes. Cephalexin and metronidazole were separately incorporated in MOF-5 post-synthetically, followed by their integration into biodegradable PLGA and PCL membranes. The pristine MOF-5 and the loaded MOFs were thoroughly characterized by FT-IR, SEM, TGA and PXRD. Drug release studies were carried out to assess the release rate of the drugs in PBS and distilled water for up to 48 hours using UV-Vis Spectroscopy. Four bacterial strains from both the Gram-positive and Gram-negative types, Staphylococus aureus, Staphylococuss epidermidis, Escherichia coli, Acinetobacter baumanii, were tested against the pristine MOF, pure drugs, loaded MOFs and the drug-loaded MOF-polymer composites. Metronidazole-loaded MOF-5 composite of PLGA (PLGA-Met@MOF-5) was found to show highest efficiency to inhibit the growth of S. epidermidis compared to the other bacteria strains while maintaining a sustained minimum inhibitory concentration (MIC). This study demonstrates that the combination of biodegradable MOF-polymer composites can provide an efficient platform for sustained and controlled release of antimicrobial drugs and can be a potential strategy to integrate them in biomedical devices.

Keywords: antimicrobial resistance, biodegradable polymers, cephalexin, drug release metronidazole, MOF-5, PCL, PLGA

Procedia PDF Downloads 134

Authors: H. H. Lee, D. Y. Kim, S. W. Lee, J. H. Kim, J. H. Kim, W. Z. Oh, S. J. Choi

Abstract:

In recent years, carbon nanotubes (CNTs) have been widely employed as a sorbent for the removal of various metal ions from water due to their unique properties such as large surface area, light mass density, high porous and hollow structure, and strong interaction between the pollutant molecules and CNTs. To apply CNTs to the sorption of Cs+ from aqueous solutions, they must first be functionalized to increase their hydrophilicity and therefore, enhance their applicability to the sorption of polar and relatively low-molecular-weight species. The objective of this study is to investigate the preparation of magnetically separable multi-walled carbon nanotubes (MWCNTs-m) as a sorbents for the removal of Cs+ from aqueous solutions. The MWCNTs-m was prepared using pristine MWCNTs and iron precursor Fe(acac)3. For the selective removal of Cs+ from aqueous solutions, the MWCNTs-m was functionalized with zinc hexacyanoferrate (MWCNTs-m-ZnFC). The physicochemical properties of the synthesized sorbents were characterized with various techniques, including transmission electron microscopy (TEM), specific surface area analysis, Fourier transform-infrared (FT-IR) spectroscopy, and vibrating-sample magnetometer. The MWCNTs-m-ZnFC was found to be easily separated from aqueous solutions by using magnetic field. The MWCNTs-m-ZnFC exhibited a high capacity for sorbing Cs+ from aqueous solutions because of their strong affinity for Cs+ and specific surface area. The sorption ability of the MWCNTs-m-ZnFC for Cs+ was maintained even in the presence of co-existing ions (Na+). Considering these results, the CNT-m-ZnFCs have great potential for use as an effective sorbent for the selective removal of radioactive Cs+ ions from aqueous solutions.

Keywords: multi-walled carbon nanotubes, magnetic materials, cesium, zinc hexacyanoferrate, sorption

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Authors: Thidarat Imyen, Paisan Kongkachuichay

Abstract:

Cu-Zn/core-shell Al-MCM-41 catalyst with various copper species, prepared by a combination of three methods—substitution, ion-exchange, and impregnation, was studied for the selective catalytic reduction (SCR) of NO with NH3 at 300 °C for 150 min. In order to investigate the effects of Zn introduction on the nature of the catalyst, Cu/core-shell Al-MCM-41 and Zn/core-shell Al-MCM-41 catalysts were also studied. The roles of Zn promoter in the acidity and the NOx adsorption properties of the catalysts were investigated by in situ Fourier transform infrared spectroscopy (FTIR) of NH3 and NOx adsorption, and temperature-programmed desorption (TPD) of NH3 and NOx. The results demonstrated that the acidity of the catalyst was enhanced by the Zn introduction, as exchanged Zn(II) cations loosely bonded with Al-O-Si framework could create Brønsted acid sites by interacting with OH groups. Moreover, Zn species also provided the additional sites for NO adsorption in the form of nitrite (NO2–) and nitrate (NO3–) species, which are the key intermediates for SCR reaction. In addition, the effect of Zn on the nature of copper was studied by in situ FTIR of CO adsorption and in situ X-ray adsorption near edge structure (XANES). It was found that Zn species hindered the reduction of Cu(II) to Cu(0), resulting in higher Cu(I) species in the Zn promoted catalyst. The Cu-Zn/core-shell Al-MCM-41 exhibited higher catalytic activity compared with that of the Cu/core-shell Al-MCM-41 for the whole reaction time, as it possesses the highest amount of Cu(I) sites, which are responsible for SCR catalytic activity. The Cu-Zn/core-shell Al-MCM-41 catalyst also reached the maximum NO conversion of 100% with the average NO conversion of 76 %. The catalytic performance of the catalyst was further improved by using Zn promoter in the form of ZnO instead of reduced Zn species. The Cu-ZnO/core-shell Al-MCM-41 catalyst showed better catalytic performance with longer working reaction time, and achieved the average NO conversion of 81%.

Keywords: Al-MCM-41, copper, nitrogen oxide, selective catalytic reduction, zinc

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Authors: Tannaz Alimardani, Amirhossein Moghanian, Morteza Elsa

Abstract:

Bioactive glasses (BGs) are a group of surface-reactive biomaterials used in clinical applications as implants or filler materials in the human body to repair and replace diseased or damaged bone. Sol-gel technique was employed to prepare a SiO₂-CaO-P₂O₅ glass with a nominal composition of 58S BG with the addition of Sr and Li modifiers which imparts special properties to the BG. The effect of simultaneous addition of Sr and Li on bioactivity and biocompatibility, proliferation, alkaline phosphatase (ALP) activity of osteoblast cell line MC3T3-E1 and antibacterial property against methicillin-resistant Staphylococcus aureus (MRSA) bacteria were examined. BGs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy before and after soaking the samples in the simulated body fluid (SBF) for different time intervals to characterize the formation of hydroxyapatite (HA) formed on the surface of BGs. Structural characterization indicated that the simultaneous presence of 5% Sr and 5% Li in 58S-BG composition not only did not retard HA formation because of the opposite effect of Sr and Li of the dissolution of BG in the SBF, but also stimulated the differentiation and proliferation of MC3T3-E1s. Moreover, the presence of Sr and Li on the dissolution of the ions resulted in an increase in the mean number of DAPI-labeled nuclei which was in good agreement with the live/dead assay. The result of antibacterial tests revealed that Sr and Li-substituted 58S bioactive glass exhibited a potential antibacterial effect against MRSA bacteria. Because of optimal proliferation and ALP activity of MC3T3-E1cells, proper bioactivity and high antibacterial potential against MRSA, BG-5/5 is suggested as a multifunctional candidate for bone tissue engineering.

Keywords: alkaline, alkaline earth, bioglass, co-doping, ion release

Procedia PDF Downloads 228

Authors: Anoff Anim, Lila A. M. Mahmoud, Maria Katsikogianni, Sanjit Nayak

Abstract:

Sustained and controlled delivery of antimicrobial drugs have been largely studied recently using metal organic frameworks (MOFs)and different polymers. However, much attention has not been given to combining both MOFs and biodegradable polymers, which would be a good strategy in providing a sustained gradual release of the drugs. Herein, we report a comparative study of the sustained and controlled release of widely used antibacterial drugs, cephalexin and metronidazole, from zinc-based MOF-5 incorporated in biodegradable polycaprolactone (PCL) and poly-lactic glycolic acid (PLGA) membranes. Cephalexin and metronidazole were separately incorporated in MOF-5 post-synthetically, followed by their integration into biodegradable PLGA and PCL membranes. The pristine MOF-5 and the loaded MOFs were thoroughly characterized by FT-IR, SEM, TGA and PXRD. Drug release studies were carried out to assess the release rate of the drugs in PBS and distilled water for up to 48 hours using UV-Vis Spectroscopy. Four bacterial strains from both the Gram-positive and Gram-negative types, Staphylococus aureus, Staphylococuss epidermidis, Escherichia coli, Acinetobacter baumanii, were tested against the pristine MOF, pure drugs, loaded MOFs and the drug-loaded MOF-polymer composites. Metronidazole-loaded MOF-5 composite of PLGA (PLGA-Met@MOF-5) was found to show highest efficiency to inhibit the growth of S. epidermidis compared to the other bacteria strains while maintaining a sustained minimum inhibitory concentration (MIC). This study demonstrates that the combination of biodegradable MOF-polymer composites can provide an efficient platform for sustained and controlled release of antimicrobial drugs and can be a potential strategy to integrate them in biomedical devices.

Keywords: antimicrobial resistance, biodegradable polymers, cephalexin, drug release metronidazole, MOF-5, PCL, PLGA

Procedia PDF Downloads 140

Authors: Hadjer Didouh, Izzaddine Sameut Bouhaik, Mohammed Hadj Meliani

Abstract:

This research delves into the intricate dynamics of biofilm adhesion on surfaces, particularly focusing on the widely employed X52 surface in oil and gas industry pipelines. Biofilms, characterized by microorganisms within a self-produced matrix, pose significant challenges due to their detrimental impact on surfaces. Our study integrates advanced molecular techniques and cutting-edge microscopy, such as scanning electron microscopy (SEM), to identify microbial communities and visually assess biofilm adhesion. Simultaneously, we concentrate on the X52 surface, utilizing impedance spectroscopy and potentiodynamic polarization to gather electrochemical responses under various conditions. In conjunction with the broader investigation, we propose a novel approach to mitigate biofilm-induced corrosion challenges. This involves environmentally friendly inhibitors derived from plants, offering a sustainable alternative to conventional chemical treatments. Our inquiry screens and selects inhibitors based on their efficacy in hindering biofilm formation and reducing corrosion rates on the X52 surface. This study contributes valuable insights into the interplay between electrochemical processes and biofilm attachment on the X52 surface. Furthermore, the outcomes of this research have broader implications for the oil and gas industry, where biofilm-related corrosion is a persistent concern. The exploration of eco-friendly inhibitors not only holds promise for corrosion control but also aligns with environmental considerations and sustainability goals. The comprehensive nature of this research aims to enhance our understanding of biofilm dynamics, provide effective strategies for corrosion mitigation, and contribute to sustainable practices in pipeline management within the oil and gas sector.

Keywords: bio-corrosion, biofilm, attachment, X52, metal/bacteria interface

Procedia PDF Downloads 48

Authors: Marinos Xagoraris, Iliada K. Lappa, Charalambos Kanakis, Dimitra Daferera, Christina Papadopoulou, Georgios Sourounis, Charilaos Giotis, Pavlos Bouchagier, Christos S. Pappas, Petros A. Tarantilis, Efstathia Skotti

Abstract:

The aim of this work was to recover phenolic compounds from grape skins produced in Greek varieties of the Ionian Islands in order to form the basis of calculations for their further utilization in the context of the circular economy. Isolation and further utilization of phenolic compounds is an important issue in winery by-products. For this purpose, 37 samples were collected, extracted, and analyzed in an attempt to provide the appropriate basis for their sustainable exploitation. Extraction of the bioactive compounds was held using an eco-friendly, non-toxic, and highly effective water-glycerol solvent system. Then, extracts were analyzed using UV-Vis, liquid chromatography-mass spectrometry (LC-MS), FTIR, and Raman spectroscopy. Also, total phenolic content and antioxidant activity were measured. LC-MS chromatography showed qualitative differences between different varieties. Peaks were attributed to monomeric 3-flavanols as well as monomeric, dimeric, and trimeric proanthocyanidins. The FT-IR and Raman spectra agreed with the chromatographic data and contributed to identifying phenolic compounds. Grape skins exhibited high total phenolic content (TPC), and it was proved that during vinification, a large number of polyphenols remained in the pomace. This study confirmed that grape skins from Ionian Islands are a promising source of bioactive compounds, suggesting their utilization under a bio-economic and environmental strategic framework.

Keywords: antioxidant activity, grape skin, phenolic compounds, waste recovery

Procedia PDF Downloads 149

Authors: Yingjeng James Li, Yun Jyun Ou, Chih Chi Hsu, Chiao-Chih Hu

Abstract:

A fuel cell is a device that produces electric power by reacting fuel and oxidant electrochemically. There is no pollution produced from a fuel cell if hydrogen is employed as the fuel. Therefore, a fuel cell is considered as a zero emission device and is a source of green power. A membrane electrode assembly (MEA) is the key component of a fuel cell. It is, therefore, beneficial to develop MEAs with high performance. In this study, an MEA for proton exchange membrane fuel cell (PEMFC) was prepared from a 15-micron thick reinforced PEM. The active area of such MEA is 25 cm2. Carbon supported platinum (Pt/C) was employed as the catalyst for both anode and cathode. The platinum loading is 0.6 mg/cm2 based on the sum of anode and cathode. Commercially available carbon papers coated with a micro porous layer (MPL) serve as gas diffusion layers (GDLs). The original thickness of the GDL is 250 μm. It was compressed down to 163 μm when assembled into the single cell test fixture. Polarization curves were taken by using eight different test conditions. At our standard test condition (cell: 70 °C; anode: pure hydrogen, 100%RH, 1.2 stoic, ambient pressure; cathode: air, 100%RH, 3.0 stoic, ambient pressure), the cell current density is 1250 mA/cm2 at 0.6 V, and 2400 mA/cm2 at 0.4 V. At self-humidified condition and cell temperature of 55 °C, the cell current density is 1050 mA/cm2 at 0.6 V, and 2250 mA/cm2 at 0.4 V. Hydrogen crossover rate of the MEA is 0.0108 mL/min*cm2 according to linear sweep voltammetry experiments. According to the MEA’s Pt loading and the cyclic voltammetry experiments, the Pt electrochemical surface area is 60 m2/g. The ohmic part of the impedance spectroscopy results shows that the membrane resistance is about 60 mΩ*cm2 when the MEA is operated at 0.6 V.

Keywords: fuel cell, membrane electrode assembly, proton exchange membrane, reinforced

Procedia PDF Downloads 294

Authors: Sandeep Kaushal

Abstract:

Tetracycline (TC) is a widespread antibiotic that is utilised in a multitude of countries, particularly China, India, and the United States of America, due to its low cost and potency in boosting livestock production. Unfortunately, certain antibiotics can be hazardous to living beings due to metal complexation and aggregation, which can lead to teratogenicity and carcinogenicity. Heterojunction photocatalysts are promising for the effective removal of pollutants like antibiotics. Herein, a simple, economical, and pollution-less hydrothermal technique was used to construct SnO₂/MnV₂O₆heterojunction with varying amounts of tin dioxide (SO₂). Various sophisticated techniques like XRD, FTIR, XPS, FESEM, HRTEM, and PLand Raman spectroscopy demonstrated the successful synthesis of SnO₂/MnV₂O₆ heterojunction photocatalysts.BET surface area analysis revealed that the as-synthesized heterojunction has a favorable surface area and surface properties for efficacious degradation of tetracycline. Under the direct sunlight exposure, the SnO₂/MnV₂O₆ heterojunction possessed superior photodegradation activity toward TC than the pristine SnO₂ and MnV2O6owing to their excellent adsorption abilities suitable band positions, large surface areas along with the effective charge-transfer ability of the heterojunction. The SnO₂/MnV₂O₆ heterojunction possessed extraordinary efficiency for the photocatalytic degradation of TC antibiotic (98% in 60 min) with an apparent rate constant of 0.092 min–1. In the degradation experiments, photocatalytic activities of as-synthesized heterojunction were studied by varying different factors such as time contact, catalyst dose, and solution pH. The role of reactive species in antibiotics was validated by radical scavenging studies, which indicated that.OH, radical has a critical role in photocatalytic degradation. Moreover, liquid chromatography-mass spectrometry (LC-MS) investigations were employed to anticipate a plausible mechanism for TC degradation.

Keywords: photocatalytic degradation, tetracycline, heterojunction, LC-MS

Procedia PDF Downloads 107

Authors: Hong-Min Kim, Da-Som Han, Myong-Hoon Lee

Abstract:

CLCs (Cholesteric liquid crystals) draw tremendous interest due to their potential in various applications such as cholesteric color filters in LCD devices. CLC possesses helical molecular orientation which is induced by a chiral dopant molecules mixed with nematic liquid crystals. The efficiency of a chiral dopant is quantified by the HTP (helical twisting power). In this work, we designed and synthesized a series of new chiral dopants having a Schiff’s base imine structure with different alkyl chain lengths (butyl, hexyl and octyl) from chiral naphthyl amine by two-step reaction. The structures of new chiral dopants were confirmed by 1H-NMR and IR spectroscopy. The properties were investigated by DSC (differential scanning calorimetry calorimetry), POM (polarized optical microscopy) and UV-Vis spectrophotometer. These solid state chiral dopants showed excellent solubility in nematic LC (MLC-6845-000) higher than 17wt%. We prepared the CLC(Cholesteric Liquid Crystal) cell by mixing nematic LC (MLC-6845-000) with different concentrations of chiral dopants and injecting into the sandwich cell of 5μm cell gap with antiparallel alignment. The cholesteric liquid crystal phase was confirmed from POM, in which all the samples showed planar phase, a typical phase of the cholesteric liquid crystals. The HTP (helical twisting power) is one of the most important properties of CLC. We measured the HTP values from the UV-Vis transmittance spectra of CLC cells with varies chiral dopant concentration. The HTP values with different alkyl chains are as follows: butyl chiral dopant=29.8μm-1; hexyl chiral dopant= 31.8μm-1; octyl chiral dopant=27.7μm-1. We obtained the red, green and blue reflection color from CLC cells, which can be used as color filters in LCDs applications.

Keywords: cholesteric liquid crystal, color filter, display, HTP

Procedia PDF Downloads 267