Electrochemical impedimetric immunosensor based on stabilized lipid bilayer-tethered WS2@MWCNT for the sensitive detection of carcinoembryonic antigen.

An innovative and ultrasensitive electrochemical impedimetric immunosensor was developed for the quantitative detection towards carcinoembryonic antigen (CEA). CEA is a widely utilized tumour biomarker that is generated in a wide variety of cancers and it is a frequently used biomarker for clinical research and early detection of cancer. Novelty of the present work is the utilization of biomimetic membrane comprising gold nanoparticle-stabilized lipid bilayer (SLB) containing DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and DOTAP (N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethyl ammonium Propane) for easy protein insertion, bio-affinity, and bio-functionalization towards the detection of CEA. The SLB is tethered on stable tungsten disulfide decorated MWCNT (WS2@MWCNT) surface for the sensitive and selective detection of CEA. The WS2@MWCNT surface has been chosen to tether SLB due to its numerous unique characteristics such as greater surface area, high conductivity, and excellent electronic conductivity, which in turn leads to the improvement of the superior electrochemical sensing ability towards CEA. The lone SLB when used for protein insertion lacks space and impedes the functional incorporation of transmembrane proteins with hydrophilic domains on both sides and biosensing applications. The SLB-tethered WS2@MWCNT surface (SLB-WS2@MWCNT) was examined by studying the electrochemical changes in the existence of redox probe K3/K4 [Fe(CN)6] through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The combined excellent properties of WS2@MWCNT and SLB have shown to amplify the sensitive detection of CEA with a LOD value of 0.2 pg mL-1. The developed sensor provides higher stability, sensitivity, and excellent reproducibility towards the detection of CEA with relative standard deviation (RSD) of < 5%. The encouraging results demonstrate that the CEA impedimetric immunosensor has potential in practical analysis and lays a solid platform for additional biomarker detection in early clinical diagnosis.

Mesoporous nickel oxide nanostructures: influences of crystalline defects and morphological features on mediator-free electrochemical monosaccharide sensor application.

Morphological and surface features are the key tools used to tune the catalytic performance of any metal oxide. In the present study, nickel oxide nanoparticles (NiO NPs) with three different morphologies were prepared using a simple hydrothermal method. The electrocatalytic performance of the prepared NiO NPs was evaluated with regard to the detection of monosaccharide glucose. The physicochemical properties of prepared NiO nanostructures were confirmed using different conventional characterization techniques. The flower-like morphological NiO NPs with nanosized petals have a high surface area and a more defective surface, resulting in improved heterogeneous catalytic activity compared to hexagonal and spherical morphological NiO NPs in glucose oxidation. The anionic and cationic vacancies on the mesoporous surface of NiO nanopetals endorsed an enhanced charge transfer efficiency compared to other NiO morphologies. The effect of scan rate, confirmed by cyclic voltammetry analysis, ensured the diffusion-controlled quasi-reversible electrochemical reaction between surface-modified electrodes and analyte. The NiO petals showed a wide linear detection range (100 nmol L-1-12 mmol L-1) and a lower detection limit of 57 nmol L-1. In addition, the anti-interference ability, repeatability, stability and real sample analysis further affirmed the enhanced catalytic features of NiO nanopetals. The results showed that defective surfaces and surface features of the NiO nanostructures could be used to tune their overall sensor performance in future applications.

α-MoO3 nanostructure on carbon cloth substrate for dopamine detection.

Orthorhombic molybdenum oxide (α-MoO3) nanostructures were deposited on the surface of carbon cloth (CC) as a flexible and high conductive scaffold by reactive RF magnetron sputtering technique. Structure and morphology of the as prepared molybdenum coated carbon cloth (MoO3CC) were thoroughly characterized with field emission scanning electron microscopy, x-ray diffraction, energy dispersive x-ray and Raman spectroscopy. Benefiting from high surface area and superior conductivity of CC as well as electrocatalytic activity of α-MoO3 nanostructures, an electrochemical sensor was fabricated. The electrochemical behavior of this new sensor toward determination of dopamine was studied in detail by cyclic voltammetry, amperometry (AM) and square wave voltammetry (SWV). Results reported here reveal that using SWV not only enhances the sensitivity of sensors to dopamine by more than 14 times compared to AM, but also offers higher linear dynamic range (1-700 µM compared to 5-550 µM). Limit of detection, for signal to noise ratio 3, was calculated to be 0.48 µM. Applicability of the proposed sensor for measurement of dopamine in real samples, like urine and pharmaceutical formulation, was also evaluated that concluded to satisfactory results.

Ecological risk assessment of silicon dioxide nanoparticles in a freshwater fish Labeo rohita: Hematology, ionoregulation and gill Na(+)/K(+) ATPase activity.

The fate and effect of nanomaterials in the environment has raised concern about their environmental risk to aquatic organisms. Silica nanoparticles (SiO2-NPs) find its uses in various fields and are inevitably released into the environment. However, the ecotoxicological effects of SiO2-NPs on the freshwater fish remain poorly understood. The aim of this study was to evaluate the effect of different concentrations (1, 5 and 25mgL(-1)) of SiO2-NPs on certain hematological, ionoregulatory and enzymological profiles of a freshwater teleost fish Labeo rohita. Hematological parameters such as hemoglobin (Hb), hematocrit (Hct), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) values were altered in SiO2-NPs treated groups. Likewise, plasma electrolytes such as plasma sodium (Na(+)), potassium (K(+)) and chloride (Cl(-)) levels and Na(+)/K(+) ATPase activity in gill of SiO2-NPs treated groups were altered in all concentrations throughout the study period (96h). The alterations of these parameters were found to be dependent on dose and exposure period. The results of the present study indicate that the alterations of these parameters may relate to physiological stress system to SiO2-NPs toxicity and also demonstrate that manufactured metal oxide NPs in aquatic environment may affect the health condition of the aquatic organisms.

Effect of gamma-ray irradiated reduced graphene oxide (rGO) on environmental health: An in-vitro and in-vivo studies.

The unique properties of reduced graphene oxide (rGO) have drawn the attention of scientists worldwide since the last decade and it is explored for a wide range of applications. However, the rapid expansion of rGO use in various products will eventually lead to environenal exposure and rises a safety concern on the environment and humal health risk. Moreover, the utilization of toxic chemicals for the reduction of graphene oxide (GO) into rGO is not environmentally friendly, warranting the exploration of non-toxic approaches. In the present work, rGO was synthesized using a different dose of gamma-ray irradiation and characterized. The in-vitro and in-vivo analysis indicated that the gamma-irradiated rGO induced toxicity depending on its degree of reduction and dosage. In the L929 cells, rGO-30 KGy significantly induced cytotoxicity even at low concentration (1 mg L-1) by inducing reactive oxygen species (ROS), lactate dehydrogenase (LDH) enzyme production, nuclear fragmentation and apoptosis. The change in morphology of the cells like membrane blebbing and cell rounding was also observed via FESEM. In the in-vivo model Caenorhabditis elegans, rGO-30 KGy significantly affected the functioning of primary and secondary targeted organs and also negatively influenced the nuclear accumulation of transcription factors (DAF-16/FOXO and SKN-1/Nrf2), neuronal health, and antioxidant defense mechanism of the nematodes. The real-time PCR analysis showed significant up-regulation (ced-3, ced-4, cep-1, egl-1, and hus-1) and down-regulation (ced-9) of the gene involved in germ-line and DNA damage-induced apoptosis. The detailed toxicity mechanism of gamma irradiated rGO has been elucidated. This work highlights the toxicity of rGO prepared by gamma-ray radiation and paves way for understating the toxicity mechanism.

One-step preparation of N-doped grapheme quantum dots with high quantum yield for bioimaging and highly sensitive electrochemical detection of isoniazid.

Conventional techniques for synthesizing GQDs have a poor quantum yield (QY) that restricts their biological applications. Herein, we present a rapid, cost-effective and high quantum yield synthesis of nitrogen-doped graphene quantum dots (N-GQDs) through a scientific microwave reactor. The reaction parameters like microwave irradiation time, temperature, precursor concentration and pressure were optimized for achieving high quantum yield. The prepared N-GQDs exhibit bright blue fluorescence and excitation independent emission property with a quantum yield of 42.81%. In-vivo investigations on C. elegans revealed that the as-prepared N-GQDs are exceptionally biocompatible and maintain the normal physiological functioning of the primary and secondary targeted organs in nematodes. The synergetic effect of intestinal barrier and defecation behavior mitigates N-GQDs translocation into reproductive organs of nematode. In addition, the N-GQDs modified GCE was tested for electrochemical sensing characteristics towards the anti-tuberculosis drug isoniazid (INZ). The N-GQDs showed appreciable electrocatalytic performance towards INZ with high sensitivity (3.76 µA µM-1 cm-1). The differential pulse voltammetry (DPV) analysis of N-GQDs exhibit a lower detection limit of 10.91 nM for INZ. The N-GQDs modified sensor exhibits good reproducibility, excellent anti-interference ability and excellent analytical performance for INZ in real samples like human blood serum and urine samples.

Highly effective and stable MWCNT/WO3 nanocatalyst for ammonia gas sensing, photodegradation of ciprofloxacin and peroxidase mimic activity.

The present study discusses the ammonia (NH3) sensing characteristics, photocatalytic degradation of emerging pollutants, and peroxidase mimic activity of multifunctional multi-walled carbon nanotube-tungsten oxide nanocomposite (MWCNT/WO3) prepared by conventional solvothermal method. The prepared MWCNT/WO3 nanocomposites were characterized by various analytical techniques like XRD, Raman, XPS, N2 adsorption, FESEM with elemental analysis and diffuse reflection spectroscopy. The prepared 1% MWCNT/WO3 nanocomposite showed better gas sensing performance for the NH3 vapors at 10-100 ppm than the pristine WO3 and the response and recover time of about 13 and 15s towards 20 ppm of ammonia (NH3) was achieved. The photocatalytic activity of MWCNT/WO3 towards organic dyes such as Rhodamine-B (Rh.B) methylene blue (MB) and pharmaceutical compound ciprofloxacin (CIP) were studied and achieved above 90% degradation at 160 min for CIP and 60 min for MB and Rho-B respectively. The radicle scavenging activity for MWCNT/WO3 nanocomposite showed the predominant formation of hydroxyl (OH•) and superoxide radicle (•O2-). Further, the MWCNT/WO3 nanocomposite showed peroxidase mimic activity and exhibit the limit of detection (LOD) of about 321 nM. From the overall analysis, MWCNT/WO3 hybrid seems to have potential characteristics that can be explored for multiple functional applications.

NiCo2O4 nanoparticles inlaid on sulphur and nitrogen doped and co-doped rGO sheets as efficient electrocatalysts for the oxygen evolution and methanol oxidation reactions.

The present work depicts the fabrication of NiCo2O4 decorated on rGO, and doped and co-doped rGO and its electrocatalytic activity towards the oxygen evolution reaction and methanol oxidation reaction. The NiCo2O4 catalyst with S-doped rGO outperformed the other catalysts, indicating that the sulphur atoms attached on rGO possess low oxophilicity and optimum free energy. This results in facile adsorption of the intermediate products formed during the OER and a rapid release of O2 molecules. The same catalyst requires an overpotential of 1.51 V vs. RHE to attain the benchmark current density value of 10 mA cm-2 and shows a Tafel slope of 57 mV dec-1. It also reveals outstanding stability during its operation for 10 h with a minimum loss in potential. On the other hand, NiCo2O4/S,N-rGO reveals superior activity with high efficiency and stability in catalyzing methanol oxidation. The catalyst delivered a low onset potential of 0.12 V vs. Hg/HgO and high current density of 203.4 mA cm-2 after addition of 0.5 M methanol, revealing the outstanding performance of the electrocatalyst.

Correction: NiCo2O4 nanoparticles inlaid on sulphur and nitrogen doped and co-doped rGO sheets as efficient electrocatalysts for the oxygen evolution and methanol oxidation reactions.

[This corrects the article DOI: 10.1039/D1NA00135C.].

Rapid one-pot synthesis of PAM-GO-Ag nanocomposite hydrogel by gamma-ray irradiation for remediation of environment pollutants and pathogen inactivation.

Designing a cost-effective, high potential and recyclable catalyst remains a challenge. In the present work, a monolithic PAM-GO-Ag hydrogel is prepared by a facile, eco-friendly method using gamma-ray irradiation. The formation of GO-Ag composite by gamma radiation is also investigated and it is authenticated by XRD, FTIR, Raman, XPS and TEM analysis. The PAM-GO-Ag hydrogel exhibits excellent catalytic activity to different catalysant like methylene blue, Rhodamine-B, and pharmaceutical compound ciprofloxacin. The high catalyst carrying capacity and rapid electron shuttling ability of GO plays a significant role in the high performance of PAM-GO-Ag hydrogel. The PAM-GO-Ag hydrogel also exhibits excellent antibacterial activity. The damaged cell membrane, protein leakage, and increased ROS level contribute to the antibacterial activity of PAM-GO-Ag. The monolithic structure of PAM-GO-Ag hydrogel makes it easy to handle, recover, and reuse for several runs without significant loss of catalytic and antibacterial activity. All these results showed the possible application of PAM-GO-Ag hydrogel as a promising catalyst for the reduction of different pollutants and antibacterial agents on a large scale with good reusability.

Enhanced electrochemical activities of morphologically tuned MnFe2O4 nanoneedles and nanoparticles integrated on reduced graphene oxide for highly efficient supercapacitor electrodes.

The morphology of a nanoparticle strongly controls the path of electronic interaction, which directly correlates with the physicochemical properties and also the electrochemical comportment. Combining it with a two-dimensional (2D) material for a layer-by-layer approach will increase its possibilities in applications such as energy conversion and storage. Here, two different morphologies of MnFe2O4, nanoparticles and nanoneedles, are developed by a facile hydrothermal approach and sandwiched with reduced graphene oxide for constructing a 2D/3D sandwiched architecture. The rGO planar structure with abundant hierarchical short pores facilitates the thorough utilization of the utmost surface area to permeate the electrolyte within the structure to minimize the accumulation of rGO nanosheets laterally. The ferrite composited with rGO manifests high specific capacitance as the EDLC behaviour surpasses the faradaic pseudocapacitance boosting electrical conductivity compared to the as-synthesized MnFe2O4 structures. Benefiting from a 3D structure and the synergetic contribution of the MnFe2O4 nanoneedles and electrically conductive rGO layer, the MnFe2O4 nanoneedles@rGO electrode exhibits a high areal capacitance of 890 mF cm-2 and a remarkable specific capacitance of 1327 F g-1 at a current density of 5 mA cm-2. 93.36% of the initial capacitance was retained after 5000 cycles in 1 mol L-1 Na2SO4 indicating its high cycling stability. The synthesis route proves to be beneficial for a comprehensive yield of MnFe2O4@rGO nanosheets of different morphologies for use in the sophisticated design of energy-storing devices. This research strongly suggests that nanoparticle geometry, in addition to two-dimensional carbon-based materials, is a critical factor in a supercapacitor design.

A nanocomposite of NiFe2O4-PANI as a duo active electrocatalyst toward the sensitive colorimetric and electrochemical sensing of ascorbic acid.

A non-enzymatic ascorbic acid sensor using a nickel ferrite/PANI (NF-PANI) nanocomposite and based on colorimetric and electrochemical sensing methods was investigated in this study. The nanocomposite was prepared by an in situ polymerization and utilized as an electrocatalyst to sense ascorbic acid (AA) through the peroxidase mimic sensing of H2O2 in the presence of 3,5,3,5-tetramethylbenzidine (TMB) as a coloring agent. It was also utilized to detect AA present in real samples prepared from fruit extracts, commercial beverages, and vitamin-C tablets. The limit of detection (LoD) for AA sensing by the peroxidase mimic method was found to be 232 nM. The relative standard deviation (RSD) calculated for analysis of the real samples analysis ranged from 1.7-3.2%. Similarly, the electrochemical sensing of AA by NF-PANI was examined by cyclic voltammetric, chronoamperometric, and differential pulse voltammetric analyses. The LoD for the electrochemical method applied to AA sensing was 423 nM. The nanocomposite functioned as an effective electrocatalytic sensing agent in both methods to selectively detect AA due to the combined effect of NF and PANI. Thus, it was shown that the nanocomposites could be utilized for the laboratory-based detection of AA by various methods and could give rapid results.

Development of BiFeO3/MnFe2O4 ferrite nanocomposites with enhanced magnetic and electrical properties.

Herein we report the development of novel multiferroic nanocomposites for their enhanced magnetic and electrical properties by employing a simple cost-effective chemical process at low temperatures. Novel perovskite-mixed spinel nanocomposites of (1 - x)BiFeO3/xMnFe2O4 where x = 0.1-0.5 have been prepared by a sol-gel auto-combustion technique. The calcination temperature was optimized and the phase formation of BiFeO3/MnFe2O4 nanocomposites was confirmed from the X-ray diffraction patterns for the samples calcined at 500 °C for 2 h. The grain sizes have been found to vary from 60 to 90 nm. The vibrational modes of the prepared nanocomposites were studied using Raman spectroscopy and FESEM and EDX were used to carry out the microstructural and composition analysis respectively. The magnetic properties seemed to have a strong dependence on the concentration of the spinel ferrite in the composite system. Saturation magnetization and coercivity exhibit an increase with increase in the MnFe2O4 content. The electrical properties from solid state impedance analysis confirm the non-Debye characteristics and the maximum activation energy is 0.931 eV for the 0.5BiFeO3/0.5MnFe2O4 nanocomposite. Dispersion in the dielectric constant and dielectric loss in the low frequency range has also been determined, which decreases with increase in temperature at lower ac frequencies.

Magnetic graphene/chitosan nanocomposite: A promising nano-adsorbent for the removal of 2-naphthol from aqueous solution and their kinetic studies.

In this study, magnetic/graphene/chitosan nanocomposite (MGCH) is prepared through facile solvothermal process and employed as an adsorbent for the removal of 2-naphthol from aqueous solution. The physico-chemical characteristic results of FESEM, Raman, FTIR, XRD and VSM confirms that the MGCH nanocomposite is effectively prepared. The FESEM and EDS analysis reveals that the high density of spherical-like Fe3O4 nanoparticles and chitosan are successfully assembled on the surfaces of the graphene sheets. VSM result of MGCH composite exhibited higher saturation magnetization of 46.5 emu g-1 and lower coercivity (Hc) of 50 Oe. This result discloses that MGCH possesses enough response required for the separation from aqueous solution. The batch mode adsorption studies demonstrates that MGCH based adsorbent showed almost 99.8% adsorption of 2-naphthol with a maximum adsorption capacity of 169.49 mg g-1 at pH 2. Moreover, the kinetic studies of the samples are performed by fitting adsorption models to ensure the nature of the adsorption system. This work proves that MGCH nanocomposite can be used as high-performance adsorbent for removing of phenolic pollutants from contaminated wastewater.

Engineering the surface of graphene oxide with bovine serum albumin for improved biocompatibility in Caenorhabditis elegans.

Graphene oxide (GO) has been extensively studied for its potential biomedical applications. However, its potential risk associated with the interactions of GO in a biological system hampers its biomedical applications. Therefore, there is an urgent need to enhance the biocompatibility of GO. In the present study, we decorated the surface of GO with bovine serum albumin (GO-BSA) to mitigate the in vivo toxic properties of GO. An in vivo model Caenorhabditis elegans has been used to study the potential protective effect of BSA decoration in mitigating GO induced toxicity. The BSA decoration on the surface of GO prevents the acute and prolonged toxicity induced by GO in primary and secondary organs by maintaining normal intestinal permeability, defecation behavior, development, and reproduction. Notably, GO-BSA treatment at 0.5-100 mg L-1 does not affect the intracellular redox status and lifespan of C. elegans. Reporter gene expression analysis revealed that exposure to GO-BSA (100 mg L-1) did not significantly influence the nuclear accumulation and expression patterns of DAF-16/FOXO and SKN-1/Nrf2 transcription factors and their downstream target genes sod-3, hsp-16.2, ctl-1,2,3, gcs-1, and gst-4 when compared to exposure to pristine GO. Also, quantitative real-time PCR results showed that GO-BSA did not alter the expression of genes involved in regulating DNA damage checkpoints (cep-1, hus-1 and egl-1) and core signaling pathways of apoptosis (ced-4, ced-3 and ced-9), in contrast to GO treatment. All these findings will have an impact on the future development of safer nanomaterial formulations of graphene and graphene-based materials for environmental and biomedical applications.

Carbon fiber based electrochemical sensor for sweat cortisol measurement.

This study examines the use of a conductive carbon fiber to construct a flexible biosensing platform for monitoring biomarkers in sweat. Cortisol was chosen as a model analyte. Functionalization of the conductive carbon yarn (CCY) with ellipsoidal Fe2O3 has been performed to immobilize the antibodies specific to cortisol. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) chemistry has been used to immobilize the antibodies onto the Fe2O3 modified CCY. Crystallinity, structure, morphology, flexibility, surface area, and elemental analysis were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FE-SEM/EDS) and Brunauer-Emmett-Teller (BET) analysis. Mechanical properties of the fiber such as tensile strength, young's modulus have also been investigated. Under optimal parameters, the fabric sensor exhibited a good linearity (r2 = 0.998) for wide a linear range from 1 fg to 1 µg with a detection limit of 0.005 fg/mL for the sensitive detection of cortisol. Repeatability, reliability, reproducibility, and anti-interference properties of the current sensor have been investigated. Detection of cortisol levels in human sweat samples has also been investigated and the results were validated with commercial chemiluminescence immunoassay (CLIA) method.

Enhanced electrochemical performances of peanut shell derived activated carbon and its Fe3O4 nanocomposites for capacitive deionization of Cr(VI) ions.

Capacitive deionization (CDI) is one of the most efficient and emerging techniques for the removal of toxic metal ions from aqueous solutions. In this study, mesoporous peanut shell derived activated carbon (PSAC) was prepared by low temperature pyrolysis at 500 °C. Subsequently, a novel iron oxide/PSAC (Fe3O4/PSAC) nanocomposite adsorbent was prepared via facile one-pot hydrothermal synthesis method at 180 °C. Nucleation growth mechanism and appropriate characterizations of prepared nanocomposites were investigated. The obtained Fe3O4/PSAC possessed a highly mesoporous structure, and a large specific surface area (680 m2/g). The electrochemical analysis showed that the obtained Fe3O4/PSAC nanocomposites exhibited higher capacitance (610 F/g at 10 mV/s), good stability and low internal resistance. A batch mode adsorption and CDI based Cr(VI) removal studies were conducted. Effects of solution pH and cycle time on Cr(VI) electrosorption capacity were further investigated. The Fe3O4/PSAC based electrodes exhibit a maximum electrosorption capacity of 24.5 mg/g at 1.2 V, which was remarkably larger than other reported materials. The fabricated composite displayed higher electrosorption capacity with rapid time and a favorable reduction of Cr (VI) to Cr(III). Studies indicated that the Fe3O4/PSAC based CDI electrode possesses a good potential to be applied for the removal of toxic metal ions from wastewater.

Porous reduced graphene oxide (rGO)/WO3 nanocomposites for the enhanced detection of NH3 at room temperature.

Incorporation of reduced graphene oxide (rGO) modifies the properties of semiconducting metal oxide nanoparticles and makes it possible to tune the surface area and pore size to optimum values, which in turn improves their gas sensing properties. In this work, to improve the ammonia (NH3) gas sensing characteristics, reduced graphene oxide (rGO) was incorporated into tungsten oxide (WO3) nanospheres using a simple ultrasonication method. The rGO-WO3 nanocomposites exhibited porous nanosheets with nanospherical WO3 as observed with field-emission scanning electron microscopy (FE-SEM). The oxidation state of the rGO-WO3 nanocomposite was determined using X-ray photoelectron spectroscopy (XPS). Three ratios of (1, 5 and 10% rGO/WO3) nanocomposites and pure WO3 showed good selectivity towards NH3 at 10-100 ppm, and more remarkably at room temperature in the range of about 32-35 °C and at a relative humidity (RH) of 55%. The limit of detection (LOD) of the synthesized rGO-WO3 nanocomposites was 1.14 ppm, which will highly favour low detection ranges of NH3. The sensor response was 1.5 times higher than that of the bare WO3 nanospheres. The sensors showed excellent selectivity, ultrafast response/recovery times (18/24 s), reproducibility and stability even after one month of their preparation. We believe that metal oxides using the rGO modifier can improve the sensitivity and reduce the LOD towards NH3 and can be used effectively in real-time environmental monitoring.

Sunlight-Induced photochemical synthesis of Au nanodots on α-Fe2O3@Reduced graphene oxide nanocomposite and their enhanced heterogeneous catalytic properties.

In this present study, we report the synthesis of Au nanodots on α-Fe2O3@reduced graphene oxide (RGO) based hetero-photocatalytic nanohybrids through a chlorophyll mediated photochemical synthesis. In this process, chlorophyll induces a rapid reduction (30 min) of Au3+ ions to Au° metallic nanodots on α-Fe2O3@RGO surface under sunlight irradiation. The nucleation growth process, photo-induced electron-transfer mechanism and physico-chemical properties of the Au@α-Fe2O3@RGO ternary nanocomposites were systematically studied with various analytical techniques. This novel photochemical synthesis process is a cost-effective, convenient, surfactant-less, and scalable method. Moreover, the prepared ternary nanocomposites enhanced catalytic activity as compared to pure α-Fe2O3 and α-Fe2O3@RGO. The advantages and synergistic effect of Au@α-Fe2O3@RGO exhibit, (i) a broader range of visible-light absorption due to visible light band gap of α-Fe2O3, (ii) lower recombination possibility of photo-generated electrons and holes due to effect of Au and (iii) faster electron transfer due to higher conductivity of RGO. Therefore, the prepared Au@α-Fe2O3@RGO hetero-photocatalytic nanohybrids exhibited a remarkable photocatalytic activity, thus enabling potential active hetero-photocatalyst for industrial and environmental applications.

Cytotoxic consequences of Halloysite nanotube/iron oxide nanocomposite and iron oxide nanoparticles upon interaction with bacterial, non-cancerous and cancerous cells.

Cytotoxic effects of iron oxide (Fe3O4) nanoparticles and Halloysite nanotube/iron oxide (HNT/Fe3O4) nanocomposite are compared based on their interaction with Gram-negative bacteria Escherichia coli and Gram-positive bacteria Bacillus subtilis. Similarly, the action of these two nanomaterials on non-cancerous Vero cell lines and human lung cancerous (A-549) cell lines are compared. The cytotoxicity studies on Fe3O4 nanoparticles and HNT/Fe3O4 nanocomposite showed difference in the rate of killing of bacterial cells. This is reflected in differential cell growth, cell membrane integrity loss, lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) production. These factors are measured over a range of concentrations of Fe3O4 nanoparticles and HNT/Fe3O4 nanocomposite and at specified time intervals, to test if there is any statistically significant difference between the toxicity of the two nanomaterials. Between the two nanomaterials, HNT/Fe3O4 nanocomposite is found to be less toxic to bacterial cells than Fe3O4 nanoparticles. HNT, when attached to the Fe3O4 nanoparticles, changes their surface characteristics and suppresses their inherent toxicity on bacteria. In the study on the effect on cell lines, Fe3O4 nanoparticles and HNT/Fe3O4 nanocomposite are both seen to be biocompatible with Vero cell lines. However, HNT/Fe3O4 nanocomposite showed more cytotoxicity than Fe3O4 nanoparticles on A-549 cell lines.