scholarly journals Physico-chemical characterization of SOA derived from catechol and guaiacol – a model substance for the aromatic fraction of atmospheric HULIS

2011 ◽  
Vol 11 (1) ◽  
pp. 1-15 ◽  
Author(s):  
J. Ofner ◽  
H.-U. Krüger ◽  
H. Grothe ◽  
P. Schmitt-Kopplin ◽  
K. Whitmore ◽  
...  
Keyword(s):  
Functional Groups ◽  
Mass Spectroscopy ◽  
Chemical Characterization ◽  
Condensation Nucleus ◽  
Chemical Diversity ◽  
Spherical Particles ◽  
Visible Range ◽  
Vis Spectroscopy ◽  
Temperature Programmed ◽  
Particle Imaging

Abstract. Secondary organic aerosol (SOA) was produced from the aromatic precursors catechol and guaiacol by reaction with ozone in the presence and absence of simulated sunlight and humidity and investigated for its properties as a proxy for HUmic-LIke Substances (HULIS). Beside a small particle size, a relatively low molecular weight and typical optical features in the UV/VIS spectral range, HULIS contain a typical aromatic and/or olefinic chemical structure and highly oxidized functional groups within a high chemical diversity. Various methods were used to characterize the secondary organic aerosols obtained: Fourier transform infrared spectroscopy (FTIR) demonstrated the formation of several carbonyl containing functional groups as well as structural and functional differences between aerosols formed at different environmental conditions. UV/VIS spectroscopy of filter samples showed that the particulate matter absorbs far into the visible range up to more than 500 nm. Ultrahigh resolved mass spectroscopy (ICR-FT/MS) determined O/C-ratios between 0.3 and 1 and observed m/z ratios between 200 and 450 to be most abundant. Temperature-programmed-pyrolysis mass spectroscopy (TPP-MS) identified carboxylic acids and lactones/esters as major functional groups. Particle sizing using a condensation-nucleus-counter and differential-mobility-particle-sizer (CNC/DMPS) monitored the formation of small particles during the SOA formation process. Particle imaging, using field-emission-gun scanning electron microscopy (FEG-SEM), showed spherical particles, forming clusters and chains. We conclude that catechol and guaiacol are appropriate precursors for studies of the processing of aromatic SOA with atmospheric HULIS properties on the laboratory scale.

scholarly journals Physico-chemical characterization of secondary organic aerosol derived from catechol and guaiacol as a model substance for atmospheric humic-like substances

2010 ◽  
Vol 10 (7) ◽  
pp. 17369-17405 ◽  
Author(s):  
J. Ofner ◽  
H.-U. Krüger ◽  
H. Grothe ◽  
P. Schmitt-Kopplin ◽  
K. Whitmore ◽  
...  
Keyword(s):  
Functional Groups ◽  
Mass Spectroscopy ◽  
Secondary Organic Aerosols ◽  
Secondary Organic Aerosol ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Chemical Diversity ◽  
Spherical Particles ◽  
Aerosol Formation ◽  
Vis Spectroscopy

Abstract. Secondary organic aerosol was produced from the aromatic precursors catechol and guaiacol by reaction with ozone in the presence and absence of simulated sunlight and humidity and investigated for its properties as a proxy for humic-like substances (HULIS). Beside a small particle size, a relatively low molecular weight and typical optical features in the UV/VIS spectral range, HULIS contain a typical aromatic and/or olefinic chemical structure and highly oxidized functional groups within a high chemical diversity. Various methods were used to characterize the secondary organic aerosols obtained: Fourier transform infrared spectroscopy (FTIR) demonstrated the formation of different carbonyl containing functional groups as well as structural and functional differences between aerosols formed at different environmental conditions. UV/VIS spectroscopy of filter samples showed that the particulate matter absorbs far into the visible range up to more than 500 nm. Ultrahigh resolved mass spectroscopy (ICR-FT/MS) determined O/C-ratios between 0.3 and 1 and main molecular weights between 200 and 500 Da. Temperature-programmed-pyrolysis mass spectroscopy identified carboxylic acids and lactones as major functional groups. Particle sizing using CNC-DMPS demonstrated the formation of small particles during a secondary organic aerosol formation process. Particle imaging using field-emission-gun scanning electron microscopy (FEG-SEM) showed spherical particles, forming clusters and chains. Hence, secondary organic aerosols from catechol and guaiacol are appropriate model substances for studies of the processing of aromatic secondary organic aerosols and atmospheric HULIS on the laboratory scale.

Comparative analysis of anti-reflection coatings on solar PV cells through TiO2 and SiO2 nanoparticles

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rajkamal Sivakumar ◽  
Prabhakaran Gopalakrishnan ◽  
Mohamed Sikkander Abdul Razak
Keyword(s):  
Refractive Index ◽  
Solar Cells ◽  
Research Work ◽  
Photon Absorption ◽  
Visible Range ◽  
Bandgap Energy ◽  
Solar Pv ◽  
Electron Hole ◽  
Content Type ◽  
Vis Spectroscopy

Purpose Photon absorbance and reflectance are the most important parameters for the recombination of electron-hole pairs. Bandgap energy plays a vital role in photon absorption. That is, the photons with energy greater than band gap energy are absorbed. Also, the refractive index of semiconductors is responsible for photon reflection, as the surface with the highest refractive index will reflect more photons than a surface with have a low refractive index. The purpose of this paper is to improvise the absorbance and reduce the reflectance of photons on the front surface of solar cells. Design/methodology/approach Photon reflection is results in reduction in electron-hole pair generation due to the high refractive index of semiconductive materials. To overcome this problem, an Anti-reflection (AR) coating of TiO2 and SiO2 is undertaken on solar cells through the Sol-spin coating method. Finally, the effectiveness of the Anti-Reflection coating is scrutinized through UV Vis-Spectroscopy, which provides details regarding reflectance, absorbance and bandgap energy characteristics. Findings UV–visible spectroscopy was used to measure the responses from the samples. The samples responded to the ultraviolet and visible range of electromagnetic radiation perfectly. UV spectroscopy was done before and after the antireflection coating of TiO2 and SiO2 over the solar cell to find their corresponding extreme reflectance and absorbance values. The effects of TiO2 and SiO2 were evaluated from the results. Originality/value In this research work, the authors have done anti-reflection coating over solar cells with nanoparticles derived from sol-gel process. Absorbance of photons observed through diffuse reflection method.

scholarly journals A Comparison Study of Functional Groups (Amine vs. Thiol) for Immobilizing AuNPs on Zeolite Surface

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 1034 ◽  
Author(s):  
Xi Rao ◽  
Michaël Tatoulian ◽  
Cédric Guyon ◽  
Stephanie Ognier ◽  
Chenglin Chu ◽  
...  
Keyword(s):  
Functional Groups ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Gold Surface ◽  
Thiol Group ◽  
Wet Chemistry ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Group 3 ◽  
Diffuse Reflectance Infrared

Immobilization of gold nanoparticles (AuNPs) on the surface of zeolite has received a great interest due to Au@zeolite’s unique characteristics and high performance for catalysis. In this work we studied the grafting of two different functional molecules; one having an amine group (3-aminopropyl)triethoxysilane (APTES) and the second having a thiol group (3-mercaptopropyl)trimethoxysilane (MPTES) on the surface of zeolite using the same wet chemistry method. The modified zeolite surfaces were characterized using zeta potential measurements; diffuse reflectance infrared fourier transform (DRIFT) and X-ray photoelectron spectroscopy (XPS). The results confirmed a successful deposition of both functional groups at the topmost surface of the zeolite. Furthermore; transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy and XPS results clearly evidenced that APTES provided a better AuNPs immobilization than MPTES as a result of; (1) less active functions obtained after MPTES deposition, and (2) the better attaching ability of thiol to the gold surface.

scholarly journals Photocatalytic activity of graphene oxide–TiO 2 thin films sensitized by natural dyes extracted from Bactris guineensis

2019 ◽  
Vol 6 (3) ◽  
pp. 181824 ◽  
Author(s):  
William Vallejo ◽  
Angie Rueda ◽  
Carlos Díaz-Uribe ◽  
Carlos Grande ◽  
Patricia Quintana
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Graphene Oxide ◽  
Photocatalytic Degradation ◽  
Photoelectron Spectroscopy ◽  
Chemical Characterization ◽  
Sem Analysis ◽  
Visible Range ◽  
X Ray ◽  
Natural Sensitizer

This study synthesized and characterized composites of graphene oxide and TiO 2 (GO–TiO 2 ). GO–TiO 2 thin films were deposited using the doctor blade technique. Subsequently, the thin films were sensitized with a natural dye extracted from a Colombian source ( Bactris guineensis ). Thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements were used for physico-chemical characterization. All the samples were polycrystalline in nature, and the diffraction signals corresponded to the TiO 2 anatase crystalline phase. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) verified the synthesis of composite thin films, and the SEM analysis confirmed the TiO 2 films morphological modification after the process of GO incorporation and sensitization. XPS results suggested a possibility of appearance of titanium (III) through the formation of oxygen vacancies (O v ). Furthermore, the optical results indicated that the presence of the natural sensitizer and GO improved the optical properties of TiO 2 in the visible range. Finally, the photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution, and pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. These results indicated that the presence of GO has an important synergistic effect in conjunction with the natural sensitizer, reaching a photocatalytic yield of 33%.

scholarly journals Bio fabrication of silver nanoparticles with antibacterial and cytotoxic abilities using lichens

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Mona A. Alqahtani ◽  
Monerah R. Al Othman ◽  
Afrah E. Mohammed
Keyword(s):  
Silver Nanoparticles ◽  
Antibacterial Activity ◽  
Synergistic Effect ◽  
Cancer Cell ◽  
Spherical Particles ◽  
Diffusion Method ◽  
Gram Positive ◽  
Gram Negative ◽  
Vis Spectroscopy ◽  
Hct 116

Abstract Recently, increase bacterial resistance to antimicrobial compounds issue constitutes a real threat to human health. One of the useful materials for bacterial control is Silver nanoparticles (AgNPs). Researchers tend to use biogenic agents to synthesize stable and safe AgNPs. The principal aim of this study was to investigate the ability of lichen in AgNPs formation and to find out their suppression ability to MDR bacteria as well as their cytotoxic activity. In the current study, lichens (Xanthoria parietina, Flavopunctelia flaventior) were collected from the south of the Kingdom of Saudi Arabia. Lichens methanolic extracts were used for conversion of Ag ions to AgNPs. Prepared biogenic AgNPs were characterized by Ultraviolet–Visible (UV–Vis) Spectroscopy, Transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) and Zeta potential and Energy-Dispersive X-ray Spectroscopy (EDS). Lichens Secondary metabolites were determined by Fourier-Transform Infrared Spectroscopy (FTIR) and Gas Chromatography–Mass Spectrometry (GC–MS). The antibacterial activity and synergistic effect of AgNPs were evaluated against pathogenic bacteria, including gram-positive; Methicillin-resistant Staphylococcus aureus (MRSA), Vancomycin-resistant Enterococcus (VRE), and gram-negative; (Pseudomonas aeruginosa, Escherichia coli) as well as the reference strains (ATCC) using the agar disk diffusion method. Cytotoxic effect of biogenic AgNPs was tested against HCT 116 (Human Colorectal Cancer cell), MDA-MB-231 (Breast cancer cell), and FaDu (Pharynx cancer cell) by MTT test. TEM imaging showed well-dispersed spherical particles of 1–40 nm size as well as zeta size showed 69–145 nm. Furthermore, FTIR and GC–MS identified various lichen chemical molecules. On the other hand, the highest antibacterial activity of AgNPs was noticed against P. aeruginosa, followed by MRSA, VRE, and E. coli. AgNPs influence on gram-negative bacteria was greater than that on gram-positive bacteria and their synergistic effect with some antibiotics was noted against examined microbes. Moreover, higher cytotoxicity for biogenic AgNPs against FaDu and HCT 116 cell line in relation to MDA-MB-231 was noted. Given the current findings, the biogenic AgNPs mediated by lichens had positive antibacterial, synergistic and cytotoxic powers. Therefore, they might be considered as a promising candidate to combat the multi-drug resistance organisms and some cancer cells.

Activation energy of copper-induced thermal degradation of chitosan acetate functional groups

2015 ◽  
Vol 35 (3) ◽  
pp. 231-239 ◽  
Author(s):  
Maria Mucha ◽  
Sylwia Ksiazek ◽  
Halina Kaczmarek
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Thermal Degradation ◽  
Functional Groups ◽  
Chemical Structure ◽  
Acetic Acid Solution ◽  
Cuo Nanoparticles ◽  
Casting Method ◽  
Modified Chitosan ◽  
Vis Spectroscopy

Abstract Thin films of chitosan acetate (CSA)-copper (II) [Cu (II)] complex were prepared by mixing Cu (II) oxide (CuO) nanoparticles in acetic acid solution of chitosan and the casting method. The changes in chemical structure of modified chitosan were confirmed by UV-Vis spectroscopy. Fourier transform infrared (FTIR) spectroscopy was applied to monitor thermal degradation processes occurring in chitosan and its composites with Cu. The changes in concentration of chitosan functional groups were observed. On a base of the kinetic constants of group thermal degradation at various temperatures, the activation energies for various groups were calculated. It was found that the presence of Cu (II) ions accelerates the thermal degradation of chitosan acetate. The higher the Cu (II) content was in the CSA matrix, the lower was the activation energy.

EFFECTS OF SPRAY PYROLYSIS DEPOSITION PARAMETERS ON MORPHOLOGICAL, OPTICAL AND STRUCTURAL PROPERTIES OF WO3 NANOSTRUCTURED THIN FILMS

2020 ◽  
Vol 27 (09) ◽  
pp. 1950203
Author(s):  
ALI AKHAVAN MAVARDIANI ◽  
MOHAMMAD BAGHER RAHMANI
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Spray Pyrolysis ◽  
Precursor Solution ◽  
Cost Effective ◽  
Solution Concentration ◽  
Visible Range ◽  
Glass Substrates ◽  
Deposition Parameters ◽  
Vis Spectroscopy

In this experimental research, tungsten trioxide (WO3) thin films were deposited using ammonium tungstate ((NH4)2WO4) by a simple and cost-effective technique of spray pyrolysis on top of glass substrates. The surface morphology, structural and optical properties of prepared samples were studied using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) pattern analysis and UV–Vis spectroscopy techniques, respectively. Studied deposition parameters were: substrate temperature (300, 350, 400, 450 and 500∘C), concentration of the precursor solution (0.01, 0.02, 0.04, 0.08, 0.1 and 0.2[Formula: see text]M), volume of the precursor solution (50, 100, 150 and 200[Formula: see text]mL) and the effect of pulsed spraying at different concentrations (0.01, 0.1 and 0.2[Formula: see text]M). FESEM images showed that the surface morphology has formed like nested micro-fibrous rings with a uniform distribution all over the surface. The XRD patterns revealed that increasing the solution concentration to 0.2[Formula: see text]M shows some peaks which can be attributed to WO3 with the hexagonal crystal structure. Transmission spectra of the samples indicate that all of the prepared samples are transparent in the visible range, with the calculated direct bandgap ranging from about 2.93[Formula: see text]eV to 3.96[Formula: see text]eV, depending on the deposition conditions.

scholarly journals Optimization of biogenic synthesis of silver nanoparticles from flavonoid-rich Clinacanthus nutans leaf and stem aqueous extracts

2020 ◽  
Vol 7 (7) ◽  
pp. 200065 ◽  
Author(s):  
Siti Nur Aishah Mat Yusuf ◽  
Che Nurul Azieyan Che Mood ◽  
Nor Hazwani Ahmad ◽  
Doblin Sandai ◽  
Chee Keong Lee ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Functional Groups ◽  
Silver Ions ◽  
Cost Effective ◽  
Aqueous Extracts ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
The Face ◽  
Clinacanthus Nutans

Background : Silver nanoparticles (AgNPs) are widely used in food industries, biomedical, dentistry, catalysis, diagnostic biological probes and sensors. The use of plant extract for AgNPs synthesis eliminates the process of maintaining cell culture and the process could be scaled up under a non-aseptic environment. The purpose of this study is to determine the classes of phytochemicals, to biosynthesize and characterize the AgNPs using Clinacanthus nutans leaf and stem extracts. In this study, AgNPs were synthesized from the aqueous extracts of C. nutans leaves and stems through a non-toxic, cost-effective and eco-friendly method. Results : The formation of AgNPs was confirmed by UV-Vis spectroscopy, and the size of AgNP-L (leaf) and AgNP-S (stem) were 114.7 and 129.9 nm, respectively. Transmission electron microscopy (TEM) analysis showed spherical nanoparticles with AgNP-L and AgNP-S ranging from 10 to 300 nm and 10 to 180 nm, with average of 101.18 and 75.38 nm, respectively. The zeta potentials of AgNP-L and AgNP-S were recorded at −42.8 and −43.9 mV. X-ray diffraction analysis matched the face-centred cubic structure of silver and was capped with bioactive compounds. Fourier transform infrared spectrophotometer analysis revealed the presence of few functional groups of phenolic and flavonoid compounds. These functional groups act as reducing agents in AgNPs synthesis. Conclusion : These results showed that the biogenically synthesized nanoparticles reduced silver ions to silver nanoparticles in aqueous condition and the AgNPs formed were stable and less toxic.

High Mobility IGZO/ITO Double-layered Transparent Composite Electrode: A Thermal Stability Study

2013 ◽  
Vol 1577 ◽  
Author(s):  
Aritra Dhar ◽  
T. L. Alford
Keyword(s):  
Thin Film ◽  
Thermal Stability ◽  
Electrical Properties ◽  
Indium Tin Oxide ◽  
High Mobility ◽  
Bottom Layer ◽  
Optoelectronic Device ◽  
Stability Study ◽  
Visible Range ◽  
Vis Spectroscopy

ABSTRACTThe fabrication of a thin film optoelectronic device involves the exposure of the transparent conductive oxide (TCO) to a high process temperature. Indium gallium zinc oxide (InGaZnO4 or IGZO) is a well known TCO with high optical transparency, moderate conductivity and high mobility. However, its electrical properties deteriorate after subsequent high temperature processes in air atmosphere. On the other hand indium tin oxide (ITO) has higher conductivity than IGZO and better thermal stability. Therefore, IGZO/ITO bilayers have been deposited on glass by radio frequency magnetron sputtering at room temperature and subsequently annealed at high temperatures in order to study their thermal stability. In the present work, a-IGZO layers with a thickness ranging from 10 nm to 100 nm were deposited over a 50 nm thick ITO layer. Results are compared with those from a single IGZO layered thin film without the ITO bottom layer. The structural, optical and electrical properties of the multilayers are studied with the use of scanning electron microscopy, UV–Vis spectroscopy and Hall measurement. An IGZO optimal thickness of 50 nm is found to improve the bilayer thermal stability at temperatures upto 400 °C keeping good opto-electrical properties. The sheet resistance for the optimized IGZO/ITO composite films is about 22 Ohm/sq, and the transmittance in the visible range is about 90%. The composite shows an excellent mobility above 40 cm2 /V-s and thus can be potentially applied as channel layer in thin film transistors (TFTs)

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