Morphology-Controlled Synthesis of α-Fe2O3 Nanocrystals Impregnated on g-C3N4-SO3H with Ultrafast Charge Separation for Photoreduction of Cr (VI) Under Visible Light.

Surface functionalization and shape modifications are the key strategies being utilized to overcome the limitations of semiconductors in advanced oxidation processes (AOP). Herein, the uniform α-Fe2O3 nanocrystals (α-Fe2O3-NCs) were effectively synthesized via a simple solvothermal route. Meanwhile, the sulfonic acid functionalization (SAF) and the impregnation of α-Fe2O3-NCs on g-C3N4 (α-Fe2O3-NCs@CN-SAF) were achieved through complete solvent evaporation technique. The surface functionalization of the sulfonic acid group on g-C3N4 accelerates the faster migration of electrons to the surface owing to robust electronegativity. The incorporation of α-Fe2O3-NCs with CN-SAF significantly enhances the optoelectronic properties, ultrafast spatial charge separation, and rapid charge transportation. The α-Fe2O3-HPs@CN-SAF and α-Fe2O3-NPs@CN-SAF nanocomposites attained 97.41% and 93.64% of Cr (VI) photoreduction in 10 min, respectively. The photocatalytic efficiency of α-Fe2O3-NCs@CN-SAF nanocomposite is 2.4 and 2.1 times higher than that of pure g-C3N4 and α-Fe2O3, respectively. Besides, the XPS, PEC and recycling experiments confirm the excellent photo-induced charge separation via Z-scheme heterostructure and cyclic stability of α-Fe2O3-NCs@CN-SAF nanocomposites.

Sonochemical synthesis and anchoring of zinc oxide on hemin-mediated multiwalled carbon nanotubes-cellulose nanocomposite for ultra-sensitive biosensing of H2O2.

In this work, the metal oxide and biopolymer nanocomposites on multiwalled carbon nanotubes (MWCNT) were prepared using a simple sonochemical method. The hexagonal nanorods of zinc oxide (ZnO NR) were synthesized by probe sonication (frequency = 20 kHz, amplitude = 50) method and were integrated on ultrasonically functionalized MWCNT-cellulose nanocrystals (MWCNT-CNC) for the first time. The stable hemin bio-composites also were prepared using the bath sonication (37 kHz of frequency, 150 W of power) method, and was used for the selective and ultrasensitive electrochemical detection of H2O2. The UV-Vis spectroscopy studies confirmed the presence of native hemin on MWCNT-CNC/ZnO NR nanocomposite. Cyclic voltammetry studies revealed that an enhanced redox electrochemical behaviour of hemin was observed on hemin immobilised MWCNT-CNC/ZnO NR nanocomposite than that of other hemin modified electrodes. Also, the MWCNT-CNC/ZnO NR/hemin modified SPCE showed 2.3 folds higher electrocatalytic activity with a lower reduction potential (-0.2 V) towards H2O2 than that of other investigated hemin modified electrodes including hemin/MWCNT and hemin/CNC-ZnO. The fabricated biosensor displayed a stable amperometric response (-0.2 V vs Ag/AgCl) in the linear concentration of H2O2 ranging up to 4183.3 µM with a lower detection limit of 4.0 nM.

Tin disulfide nanorod-graphene-ß-cyclodextrin nanocomposites for sensing dopamine in rat brains and human blood serum.

In the present work describes a facile synthesis of tin disulfide (SnS2) nanorods decorated graphene-ß-cyclodextrin (SnS2/GR-ß-CD) nanocomposite for robust and novel dopamine (DA) electrochemical biosensor applications. The DA biosensor was fabricated using the glassy carbon electrode (GCE) modified with SnS2/GR-ß-CD nanocomposite. The sonochemical and hydrothermal methods have been used for the synthesis of SnS2/GR-ß-CD. Different physicochemical methods were used to confirm the formation of the GR-ß-CD, SnS2, and SnS2/GR-ß-CD nanocomposite. The cyclicvoltammetric cathodic current response of DA was 5 folds higher than those observed at bare, ß-CD, SnS2-ß-CD, and GR-ß-CD modified GCEs. Under optimised conditions, the biosensor's DPV response current is linear to DA from the concentration of 0.01-150.76 µM. The detection limit of the biosensor was 4 nM. The SnS2/GR-ß-CD biosensor shows an excellent selectivity towards DA in the presence of common interfering species, including ascorbic acid and uric acid. Also, the as-prepared nanocomposite-modified electrode exhibited satisfactory long-term stability, sensitivity (2.49 µAµM-1 cm-2) along with reusability for detection of DA. The fabricated SnS2/GR-ß-CD biosensor was successfully used for the detection of DA in the rat brain and human blood serum samples.

Sonochemical synthesis of gum guar biopolymer stabilized copper oxide on exfoliated graphite: Application for enhanced electrochemical detection of H2O2 in milk and pharmaceutical samples.

A novel and cost-effective synthesis of biopolymer-based organic and inorganic composite materials have received substantial attention in a broad range application including electroanalysis of small molecules. In this perspective, we report the synthesis of gum guar (guar) biopolymer stabilized cupric oxide decorated on exfoliated graphite (GR-guar/CuO) composite. Different physicochemical characterization methods were used to confirm the successful exfoliation of graphite and formation of the GR-guar/CuO composite. A simple sonochemical method has been used for the preparation of guar stabilized exfoliated graphite (GR-guar). The flower-like CuO on GR-guar and guar stabilized CuO (CuO-guar) composites were synthesized using a hydrothermal method. Cyclic voltammetric studies revealed that the GR-guar/CuO composite modified screen-printed carbon electrode (SPCE) had enhanced electro-reduction ability towards H2O2 than GR-guar and pristine graphite/CuO-guar modified SPCEs. Under optimized experimental conditions, the GR-guar/CuO composite modified electrode detects H2O2 in the response ranges from 0.02 to 1296.6 µM. The sensor shows a lower detection limit of 5.8 nM with high sensitivity. The as-prepared GR-guar/CuO composite sensor is highly reproducible and had excellent selectivity and practicality towards the detection of H2O2. Consequently, the fabricated sensor can be used for the accurate detection of H2O2 in real samples.

Facile synthesis of cellulose microfibers supported palladium nanospindles on graphene oxide for selective detection of dopamine in pharmaceutical and biological samples.

The cost-effective synthesis of novel functional nanomaterials has received significant attention in the physical and chemical sciences due to their improved surface area, high catalytic activity along with unique morphological features. This paper reports a facile and eco-friendly synthesis of spindle-like palladium nanostructures (PdSPs) on graphene oxide-cellulose microfiber (GO-CMF) composite for the first time. The GO-CMF/PdSPs composite was synthesized by an electrochemical method without the use of additional surfactants and capping agents. The synthesized materials were characterized and confirmed by using transmission electron microscopy, high-resolution scanning electron microscopy, X-ray diffraction spectroscopy, Raman spectroscopy and Fourier-transform infrared spectroscopy. As-synthesized GO-CMF/PdSPs composite modified electrode was used as a selective electrocatalyst for the oxidation of dopamine (DA). The electrochemical redox behaviors of DA were investigated using cyclic voltammetry (CV). The CV results revealed that the GO-CMF/PdSPs composite modified electrode has 10 folds enhanced oxidation current response to DA than GO, PdSPs and GO-CMF modified GCEs. Under optimized conditions, the GO-CMF/PdSPs composite sensor exhibits a linear response to DA in the concentration range from 0.3 to 196.3 µM with the lower detection limit of 23 nM. The nanocomposite electrode also shows promising features towards the reliable and selective detection of DA, which includes high stability, reproducibility and high selectivity towards the commonly interfering species such as ascorbic acid, uric acid, and dihydroxybenzene isomers. The sensor was successfully tested for the real-time detection of DA in the commercial DA injections and human serum samples.

Novel electrochemical synthesis of cellulose microfiber entrapped reduced graphene oxide: A sensitive electrochemical assay for detection of fenitrothion organophosphorus pesticide.

Over the past decades, the synthesis of carbohydrate polymers incorporated graphene or reduced graphene oxide has received greater attention in different disciplines owing to their unique physicochemical properties. In this context, we report a facile electrochemical synthesis of cellulose microfibers supported reduced graphene oxide and its application towards enhanced and lower potential electrochemical detection of fenitrothion. The synthesized cellulose microfibers supported reduced graphene oxide composite was further characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy and high resolution scanning electron microscopy. Cyclic voltammetry studies reveal that cellulose microfibers supported reduced graphene oxide composite modified screen-printed carbon electrode exhibits a superior electro-reduction ability and lower reduction potential towards fenitrothion compared to screen-printed carbon electrodes modified with graphene oxide, graphene oxide-cellulose microfibers, and reduced graphene oxide. Furthermore, cellulose microfibers supported reduced graphene oxide composite modified electrode showed 141 mV lower reduction potential towards fenitrothion than the chemically reduced graphene oxide- cellulose microfibers composite modified screen-printed carbon electrode. The effect of accumulation time, catalyst loading, scan rate and pH for the detection of fenitrothion has been studied and discussed. Differential pulse voltammetric studies show that the fabricated composite electrode can detect the fenitrothion in a wider linear response range up to 1.134 mM with a detection limit of 8 nM. To validate the proof of concept, the fabricated sensor was successfully applied for the detection of fenitrothion in different water samples.

Enhanced reversible redox activity of hemin on cellulose microfiber integrated reduced graphene oxide for H2O2 biosensor applications.

In recent years, the carbohydrate polymers incorporated composite materials have shown significant interest in the bioanalytical chemistry due to their enhanced catalytic performances of various enzymes or mimics. This paper reports the fabrication of novel H2O2 biosensor using a hemin immobilized reduced graphene oxide-cellulose microfiber composite (hemin/RGO-CMF). The RGO-CMF composite was prepared by the reduction of GO-CMF composite using vitamin C as a reducing agent. Various physio-chemical methods have applied for the characterization of RGO-CMF composite. Cyclic voltammetry results revealed that the hemin/RGO-CMF composite shows a better redox electrochemical behavior than hemin/RGO and hemin/GO-CMF. Under optimized conditions, the hemin/RGO-CMF composite exhibit a linear response to H2O2 in the concentration range from 0.06 to 540.6 µM with the lower detection limit of 16 nM. The sensor also can able to detect the H2O2 in commercial contact lens solution and milk samples with functional recovery, which authenticates the potential ability in practical sensors.

Degradation of Methylene Blue Dye in the Presence of Visible Light Using SiO2@α-Fe2O3 Nanocomposites Deposited on SnS2 Flowers.

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS2 (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO2@α-Fe2O3 nanocomposites were then deposited on the top of the SnS2 flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV⁻Vis Spectroscopy, Brunauer⁻Emmett⁻Teller (BET) surface area analysis, and photoluminescence (PL) spectroscopy. The photocatalytic behavior of the SnS2-SiO2@α-Fe2O3 nanocomposites was investigated by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt % SiO2@α-Fe2O3 nanocomposites on SnS2 flowers.