Narrow Results

Amorphous carbon nitride (a-CN_x) films were deposited on quartz substrates by newly developed surface wave microwave plasma chemical vapor deposition (SWMP-CVD) of alcohol camphoric carbon plasma source at room temperature. Then the a-CN_x films were heat-treated at various annealing temperatures (AT) in the 100–500°C range. The effects of heat treatment on the structural modifications were studied by Visible-Raman spectroscopy through the evolution of D and G peaks. The spectral evolution observed on heat-treated a-CN_x shows progressive formation of crystallites. Raman spectra have revealed the amorphous structure of as-grown a-CN_x films and the growth of nanocrystallinity upon increase of AT. These structural changes were further correlated with optical band gap and fraction of sp³ bonded carbons present, derived respectively from the UV-visible and photoelectron spectroscopy. The wide range of optical absorption coefficient characteristics is observed depending on the AT. The optical band gap of as-grown a-CN_x films is found to be approximately 2.8 eV; it gradually decreases to 2.5 eV for the films heat-treated at 300°C and then it decreases rapidly to 0.9 eV at 500°C. The results obtained are discussed and compared with the literatures.

A new series of multi-walled carbon nanotube reinforced polybenzoxazine (MWCNT/PBZ) nanocomposites was successfully designed and developed. Three different maleimido terminal benzoxazine monomers (MI-BZs) were synthesized using N-(4-hydroxyphenyl) maleimide (HPM) and formaldehyde solution through Mannich condensation reaction and were characterized by FT-IR and NMR spectroscopy. Varying weight percentages (0 wt.%, 0.5 wt.%, 1.0 wt.% and 1.5 wt.%) of glycidyl-MWCNT were then incorporated into benzoxazine matrices to prepare MWCNT/PBZ nanocomposites. The nanocomposites having higher weight percentage of MWCNT were found to possess excellent thermal properties than those of neat PBZs. The developed nanocomposites exhibited better flame retardancy and higher dielectric constant. The optical properties ascertained from the UV-Vis absorption bands at the region of 300–350 nm and strong fluorescent emissions were observed in the wavelength range of 300–550 nm from Photoluminescence analysis. The intensity of characteristic diffraction peaks corresponding to g-MWCNT confirmed the reinforcement of MWCNT in the benzoxazine matrices, which indicated the successful formation of nanocomposites. The morphological studies ascertain the compatibility and uniform dispersion of MWCNT in the PBZ network.

Cheap and efficient dye sensitized solar cells (DSSCs) can be prepared using natural dyes responding in the visible region of solar spectrum. Localized surface plasmon resonance (LSPR) plays a very important role for the improvement in the efficiency of DSSCs by using Plasmonic nanoparticles (PNPs) for exploiting the visible portion of the solar radiation by transferring the energy from dye to PNP. This energy transfers from dye to semiconductor TiO₂ through PNP which increases the overall photo catalytic activity. In the present study, Al-doped TiO₂ photoanodes were prepared via sol–gel route and used for DSSC application. Various natural and synthetic dyes are prepared and the optical transmittance and absorbance of the dyes are measured in the wavelength range of 250–850nm using UV-Vis spectroscopy and they are used in DSSC. Natural dyes extracted from fruits and synthetic dye based on Ruthenium (Ru) metal complex is used as sensitizers. Power conversion efficiency (PCE) of solar cells utilizing different dyes is compared. Out of the various natural dyes, beetroot and strawberry extracts based dyes show good absorbance in the visible range of electromagnetic spectrum. On the other hand, synthetic dyes based on Ru complex show strong absorbance over a wide range of visible spectrum. The absorbance increases with increase in concentration of Ru in ethanol. The extracts of beetroot, strawberry and mixed fruits show a peak in absorbance spectra at 501nm, 416nm and 332nm, respectively, indicating the absorption over a wide range of visible spectrum. Maximum efficiency of DSSCs utilizing PNPs sensitized with beetroot and strawberry dyes are found to be 1.5% and 1.3%, respectively.

Theoretical and experimental results on the formation of gold nanoparticles under the influence of pulsed nanosecond laser irradiation of aqueous AuCl${}_4^{-}$ solution are presented. It is shown that high monodispersity of nanoparticles ensemble is related to the strong dependence of total absorbance of laser radiation on nanoparticles diameter and the conductive heat transfer to surrounding medium.

A water-chloroform interface was developed for the synthesis and assembly of the cadmium-mediated multiporphyrin arrays. With the use of a vertical dipping method, multilayers of the multiporphyrin can be deposited onto hydrophobic substrate surfaces. An in situ absorbance measurement at the water-porphyrin chloroform interface revealed a blue shift for the porphyrin Soret band after the addition of CdCl₂ into the water phase. The transferred multilayers showed a broad Soret band from 430 to 442 nm, which is ascribed to monomer-like porphyrin arrangement in the planar layer and aggregates in the interlayer. The orientation angle of porphyrin macrocycles is about 30°. The porphyrin emission properties in the present multilayers are compared to those in the monomer and aggregate prepared from the air-water/CdCl₂ subphase surfaces.

Noninvasive glucose monitoring development is critical for diabetic patient continuous monitoring. However, almost all the available devices are invasive and painful. Noninvasive methods such as using spectroscopy have shown some good results. Unfortunately, the drawback was that the tungsten halogen lamps usage that is impractical if applied on human skin. This paper compared the light emitting diode (LED) to traditional tungsten halogen lamps as light source for glucose detection where the type of light source plays an important role in achieving a good spectrum quality. Glucose concentration measurement has been developed as part of noninvasive technique using optical spectroscopy. Small change and overlapping in tungsten halogen results need to replace it with a more convenient light source such as LED. Based on the result obtained, the performance of LED for absorbance spectrum gives a significantly different and is directly proportional to the glucose concentration. The result shows a linear trend and successfully detects lowest at 60 to 160 mg/dL glucose concentration.

In this paper, we have discussed for the first time a detailed electronic absorption study of the mono-azo dye Direct Yellow 27 [C${}_{25}$H${}_{20}$N₄Na₂O₉S₃] (DY-27) with five different homogeneous media by applying experimental and theoretical techniques along with some new characteristics of DY-27 in the field of solar cells as well as antiviral activities. A clear absorption band in the UV-visible region was observed, although the absorption maxima lie in the visible region. The electronic absorption transitions observed in our study were fully spin and symmetry allowed transitions with $\pi$–${\pi }^{\ast }$ character. Time-dependent density functional theory (TD-DFT) analysis has been done for understanding the electronic and the charge transfer performance. Moreover, the impacts of polar protic and polar aprotic solvents in the structural variation of DY-27 have been reported here. Further, applications of the dye in the field of solar cell, as well as antiviral activity, were performed using molecular modeling approaches. The dye exhibited a D–$\pi$–A–A structure with a high light-harvesting efficiency (LHE) and good injection efficiency acts as an effective dye sensitized solar cell (DSSC). Molecular docking studies of the dye DY-27 performed with M-protease of the different corona viruses, MERS, SARS-CoV-1 and SARS-CoV-2 indicated comparable binding energies with the controlled inhibitors and best interactions are observed for the SARS-CoV-1.

Lanthanum (La) and cerium (Ce) atom-adsorbed graphene systems are investigated for a thorough understanding of the strongly coupling effects associated with the very complicated quasi-particle 4f orbital charges and spin configurations, such as the significant covalent bonds of C-sp3 and La-5d5/Ce-4f7 orbitals and their non-magnetic/ferromagnetic spin configurations. Their quasi-particle behaviors are expected to present a sharp contrast with those observed in alkalizations, oxidations, and halogenations.