An efficient chemical sensor based on CeO2 nanoparticles for the detection of acetylacetone chemical

Evaluation of phytoactive contents and antibacterial activities of green synthesised cerium oxide nanoparticles using Melastoma sp. leaf extract as the capping agent

Simple and green methods of developing nanoparticles (NPs) have attracted the attention of researchers. Literature on utilising leaf extract to prepare cerium oxide (CeO2 NPs) is scarce. The present study synthesised leaf-mediated-CeO2 NPs to produce nanopowders of controllable sizes for further applications. The study is the first to report the optimised parameters (pH 7, 5 g/150 mL concentration of the leaf extract, and 3 h of reaction time) of procuring CeO2 NPs using Melastoma sp. leaf extract as the capping agent with excellent properties. The absorbance of the NPs suspension obtained in this study was recorded at approximately 252 nm with Ultraviolet-Visible (UV-Vis) Spectroscopy. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) were also utilised to characterise and confirm the CeO2 NPs prepared. The XRD spectra documented the purity of the NPs at specific diffraction patterns, while TEM revealed the spherical form of the NPs with a particle size of 16 nm. The formation of CeO2 NPs has been confirmed from the FTIR spectra procured, which exhibited a Ce-O peak at 555 nm. Phytochemical screening test and FT-IR analysis of leaf extract revealed the existence of flavonoids, terpenoids, sugars, saponins, quinones, and glycosides. The NPs suspensions of varying concentrations (control, 50, 100, 150, 200, and 250 μg/mL) were prepared and employed for evaluations against Gram-positive and -negative bacteria. Resultantly, CeO2 NPs demonstrated antibacterial activities against both bacteria types. The highest antibacterial activities were recorded against E. coli and K. pneumonia at 1.83 ± 0.137 and 1.83 ± 0.14 mm maximum inhibition zones, respectively, at 250 mg/uL of the NPs.

Nanostructured SnO2 Thin Films Based on a Convenient Chemical Deposition for Sensitive Detection of Ethanol

A specific matrix sensor that can operate at low temperatures and has a high sensing response is crucial for monitoring flammable VOC gases. In this study, a nanostructured SnO2 thin film was successfully produced using a suitable chemical deposition method, and its sensing properties were comprehensively analyzed. The SEM images revealed that the thin film of the nanostructured SnO2 is made up of two different sizes of broccoli-like structure nanoparticles. The sensor, which is based on this unique micronano structure, demonstrated a high sensing response (44), low operating temperature (200 °C), and fast response time (6s). Additionally, the nanostructured sensor exhibited excellent resistance to humidity interference and long-term stability. Moreover, DFT is employed to evaluate the electronic properties and to systematically explain the gas sensing mechanism of the nanostructured sensor based on the SnO2 thin film.

Template-Less and Surfactant-Less Synthesis of CeO2 Nanostructures for Catalytic Application in Ipso-hydroxylation of Aryl Boronic Acids and the aza-Michael Reaction

Due to its excellent physicochemical properties, CeO₂ has found great importance as an electrochemical and in electronics, photocatalysis, sensing, and heterogeneous catalysis. Herein, we report the surfactant-less and template-less synthesis of CeO₂ nanostructures by the hydrothermal method. The synthesized CeO₂ nanostructures have been characterized in detail by electron microscopy, spectroscopy, diffractometry, and other analytical methods. The XRD studies revealed the formation of pure crystalline CeO_2, possessing a cubic fluorite structure with an average crystallite size of 15.6 to 16.4 nm. Electron microscopy studies reveal the formation of cube-shaped CeO₂ nanostructures with sizes below 25 nm. The cube-shaped CeO₂ nanostructures exhibited a higher BET surface area compared to their bulk counterparts. The XPS analysis has confirmed the existence of Ce in the mixed oxidation states of +3 and +4, while O is present as O^2- in the sample. The as-synthesized CeO₂ nanostructures exhibit excellent catalytic activity in both the ipso-hydroxylation of aryl boronic acids and the aza-Michael reaction. The analysis of the used catalyst has confirmed its stability under the reported reaction conditions. The catalysts retain their catalytic activity up to the fifth run in both types of reactions, which is economically beneficial for industrial application.

Electrochemical detection of hydrogen peroxide using micro and nanoporous CeO2 catalysts

In this research work, focus has been made on a glassy carbon electrode (GCE) modified commercial micro and synthesized nano-CeO₂ for the detection of hydrogen peroxide (H₂O₂). Firstly, CeO₂ nanoleaves were prepared by solvothermal route. Both commercially available micro CeO₂ and synthesized nano-CeO₂ structures were analyzed by different characterization techniques. The Raman spectra of synthesized nano CeO₂ has more oxygen vacancies than micro CeO₂. SEM images revealed that the synthesized CeO₂ acquired leaf-like morphology. The catalyst nano CeO₂ offered mesoporosity from nitrogen adsorption-desorption isotherms with massive sites of activation for increasing efficiency. Experiments on determining H₂O₂ using micro CeO₂ or nano-CeO₂/GCE was conducted using cyclic voltammetry (CV) and amperometry. Enhanced H₂O₂ reduction peak current with lower potential was observed in nano-CeO₂/GCE. The influence of scan rate and H₂O₂ concentration on the performance of nano-CeO₂/GCE were also studied. The obtained results have indicated that nano-CeO₂/GCE showed improved electrochemical sensing behavior towards the reduction of H₂O₂ than micro-CeO₂/GCE and bare GCE. A linear relationship was obtained over 0.001 μM-0.125 μM concentration of H₂O₂, with good sensitivity 141.96 μA μM^-1 and low detection limit of 0.4 nM. Hence, the present nano-CeO₂ system will have a great potential with solvothermal synthesis approach in the development of electrochemical sensors.

CeO2 quantum dots for highly selective and ultrasensitive fluorescence detection of 4-nitrophenol via the fluorescence resonance energy transfer mechanism

A rapid and simple fluorescence probe based on CeO₂ quantum dots (QDs) was developed for highly selective and ultrasensitive direct determination of 4-nitrophenol (4-NP). CeO₂ QDs were prepared using the sol-gelmethod with the precursor of Ce(NO₃)₃·6H₂O as a cerium source. The products were characterized through high-resolution electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The fluorescent probe based on CeO₂ QDs exhibited a broad linear response to the concentration of 4-NP in the range of 0.005-75.00 μM and provided a low detection limit of 1.50 nM. The fluorescence of CeO₂ QDs was quenched by 4-NP through the fluorescence resonance energy transfer mechanism owing to the well overlaps between the fluorescence emission spectrum of CeO₂ QDs with the ultraviolet absorption spectrum of 4-NP. This result was confirmed by the time-resolved fluorescence spectra and the evaluation of the interaction distance between CeO₂ QDs and 4-NP. The prepared CeO₂ QDs are successfully applied to the determination of 4-NP in real water samples, where the spiked recoveries range from 98.2% to 102.4%.

Upshot of Concentration of Zirconium (IV) Oxynitrate Hexa Hydrate on Preparation and Analyses of Zirconium Oxide (ZrO₂) Nanoparticles by Modified Co-Precipitation Method

In the present work, pure nanocrystalline monoclinic Zirconia (ZrO₂) has been successfully synthesized and optimized by the modified co-precipitation method. The concentration of raw material has been optimized with the fixed amount of precipitation agent (Potassium hydroxide KOH). The thermal history of the precursor has been examined through TG/DTA analysis. All the samples are subjected to study the structure, fingerprints of the molecular vibrations, and morphology analyses. The representative sample has been analyzed through Transmission Electron Microscope (TEM) and X-ray Photo Electron Spectroscopy (XPS) analyses. The as-prepared sample exhibits the better crystallinity and surface morphology with lesser particle size (190 nm) when the raw material concentration is 0.2 M. The as-prepared ZrO₂ filler (0, 3, 6, 9, and 12 wt.%) is spread through the enhanced polymer electrolyte P(S-MMA) (27 Wt.%)-LiClO₄ (8 wt.%)-EC + PC (1;1 of 65 wt.%) complex system via solution casting method. The as-synthesized electrolyte films are examined via complex impedance analysis. P(S-MMA) (27 wt.%)-LiCIO₄ (8 wt.%)-EC + PC (1 ;1 of 65 wt.%)-6 wt.% of ZrO₂ shows the high ionic conductivity 2.35 × 10^-3 Scm^-1. Temperature-dependent ionic conductivity studies obey the non-linear behavior. The enhanced ZrO₂ has been expected to enhance the other electrochemical properties of the lithium secondary battery.