Employable metal (Ag & Pd)@MIL-125-NH2@cellulose acetate film for visible-light driven photocatalysis for reduction of nitro-aromatics.

A scalable process for the production of Ag nanoparticles that gives complete conversion of the limiting reactant is analyzed in detail. The kinetics of silver nanoparticle synthesis using citrate reduction are investigated and used for development of a reaction engineering model to facilitate the reactor design. The effect of temperature, pH, concentration and mixing (axial dispersion) on the rates of nucleation and growth are analyzed quantitatively. An approach that considers reaction kinetics coupled with quality of dispersion is developed for reactor design as well as selection of reactor configurations for the synthesis of specific particle sizes. The developed approach has been used for continuous production of 10 L suspension Ag nanoparticles with very narrow particle size distribution.

Reaction Engineering for Continuous Production of Silver Nanoparticles

Spray pyrolysis deposited In2S3 thin films exhibit two prominent photoluminescent emissions. One of the emissions is green in color and centered at around ∼ 540 nm and the other is centered at around ∼ 690 nm and is red in color. The intensity of the green emission decreases when the films are subjected to annealing in air or vacuum. The intensity of red emission increases when films are air annealed and decreases when vacuum annealed. Vacuum annealing leads to an increase in work function whereas air annealing leads to a decrease in work function for this thin film system relative to the as deposited films indicating changes in space charge regions. Surface photovoltage analysis using a Kelvin probe leads to the conclusion that inversion of band bending occurs as a result of annealing. Correlating surface contact potential measurements using a Kelvin probe, x-ray photoelectron spectroscopy and photoluminescence, we conclude that the surface passivation plays a critical role in controlling the photoluminescence from the spray pyrolysis deposited for In2S3 thin films.

Photoluminescence in Spray Pyrolysis Deposited β-In 2 S 3 Thin Films

Diabetes is a serious disease with a huge number of patients worldwide. Glucose levels in people with diabetes are above 6.6 mM in blood samples and 200 μM in saliva samples. Metal-organic frameworks (MOFs) have outstanding properties for glucose sensors, such as a large surface area and being rich in active sites. In this research, a silver [email protected] ([email protected]) composite was synthesized through one-pot synthesis using a microwave at 130 °C for 1 hour at 200 W. The results showed that the 4%[email protected] carbon paste electrode obtained better sensor performance than Ni-BTC with a limit of detection (LoD) of 14.73 μM, a sensitivity of 6584.89 μA mM−1 cm−2, and a linear range of 10–1250 μM. The 4%[email protected] carbon paste electrode also had better stability than Ni-BTC and had good reproducibility. Glucose detection tests on salivary samples showed that the 4%[email protected] carbon paste electrode could be used to measure glucose levels in salivary samples. 

Facile One-Pot Microwave-Assisted Synthesis of Rod-Like and Hexagonal Plate-Like AgNP@Ni-BTC Composites for a Potential Salivary Glucose Sensor

Preparation and application of ecofriendly materials is becoming an urgent topic. In this work, a green approach for producing silver nanoparticles (AgNPs) embedded on natural Populus fibers (PF) was developed based on hydrothermal synthesis using polyamidoxime (PAO)-functionalized fibers (PF–g–PAO). Throughout the production process, PAO acts as a trapping, stabilizing, and reducing agent for AgNPs formation without involvement of any additional reagents. The effects of the hydrothermal synthesis temperature and PF–g–PAO immersion duration in silver ion solution on AgNPs formation were studied based on the morphology of the PF–g–PAO/AgNPs composites, and their application in catalytic reduction of 4-nitrophenol (4-NP) was investigated using scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) spectrophotometry. Under the optimal reaction condition, AgNPs with average size of 36 nm were embedded on the PF surface with high silver content (15.6 wt%), exhibiting high catalytic activity (2.40 s−1 g−1) and reusability (>5 cycles) in reduction of 4-NP to 4-aminophenol (4-AP). More importantly, the use of the renewable resource cellulose in this work represents a sustainable feature to reduce manufacturing cost and environmental impact.

Green planting silver nanoparticles on Populus fibers and the catalytic application

Silver nanoparticles are synthesized using N,N dimethyl formamide (DMF) both as reductant as well as solvent. The reaction is performed in the presence and absence of surfactants at room temperature to know the effect of the same on the size and shape of the silver nanoparticles. In this regard, two different surfactants viz. polyvinylpyrolidone (PVP) and cetyl trimethyl ammonium bromide (CTAB) are used. The rate of the reaction and the formation kinetics is continuously monitored by UV-vis spectroscopy at regular time intervals. The corresponding change in plasmonic peaks and full width half maxima (FWHM) is studied in detail. The particle size is determined using Mie plot.

Kinetics of Silver Nanoparticle Growth Using DMF as Reductant – Effect of Surfactants

The oxide thickness is of great concern today. The basic idea is to grow SiO2 layer on Silicon. The oxide is grown on intrinsic silicon substrate by thermal oxidation i.e., wet oxidation and dry oxidation. The thickness is compared for both the oxidation processes after different oxidation cycles. The capacitance per unit length is also calculated for the oxide growth in above. The percentage oxide thickness is also estimated and the oxide is found to grow more into the substrate with time and number of cycles.

Numerical simulation of dry and wet oxidation of Silicon by TCAD Sprocess

We report on the exciton–plasmon interaction and fluorescence resonance energy transfer controlled photoluminescence quenching and switching in β-In2S3 microflowers dispersed in Au nanoparticle colloid. The strong resonant interaction of excited β-In2S3 microflowers with the surface plasmons of Au nanoparticles (~520 nm) lead to shift in the excitonic binding energy (2.4 eV) with a magnitude of ~50 meV. In the proximity of Au nanoparticles, the broad emission spectrum of β-In2S3 microflowers with prominent peak at wavelength of ~540 nm is quenched and the peak switches to wavelength of ~600 nm. We demonstrate that the quenching and switching of emission band depends on the rate of fluorescence resonance energy transfer, extent of spectral overlap and β-In2S3 microflowers (donor)- Au nanoparticles (acceptor) distance. This study opens the wide possibility of fabricating sensors and photonic devices with tunable optical properties.

https://iopscience.iop.org/article/10.1088/2053-1591/3/6/065016/pdf

Chithra Parameswaran

Papers

Kinetics of Silver Nanoparticle Growth Using DMF as Reductant – Effect of Surfactants

Numerical simulation of dry and wet oxidation of Silicon by TCAD Sprocess

FRET controlled photoluminescence in β-In2S3 microflower—Au nanoparticle ensemble