Fabrication of 2D+1D nanoarchitecture for transition metal oxide modified CdS nanorods: A comparative study on their photocatalytic hydrogen-generation efficiency.

We report the formation of Mo1-xWxO3-CdS (0 ≤ x ≤1) nanophotocatalysts by a combination of solid-state and solution-impregnation processes. The formation of 2D+1D heterostructured composite was revealed by electron microscopy and the structure of ternary co-catalyst and photocatalysts were confirmed by spectroscopic analyses. The H2evolution activity of the nanocomposites was assessed via photocatalytic splitting of water under the irradiation of visible light. All the nanocomposites studied here exhibit notable catalytic activity and good photostability using lactic acid as the sacrificial electron donor compared to a pristine compound. Among these nanocomposites, WO3-CdS shows superior activity with H2evolution rates of 15.19 mmolg-1h-1, 28 times higher than the pure CdS. The WO3-CdS photoactivity is not only superior among all the composites studied here but also highest among the reported WO3composite catalysts to date. The novel construction of the oxide-based nanocomposite photocatalyst shown here efficiently enhances the catalytic activity by effective separation of charge carriers and inhibits photocorrosion of CdS nanorods. The apparent quantum yield of the hydrogen evolution for WO3-CdS was found to be 8% in the visible spectral range. The disparity of the catalytic ability between MoO3and WO3and the variance among the compositions was unraveled through optical band-offset alignment with respect to CdS. Though the 2D+1D novel fabrication is common to all the composites, the difference in the type of band alignment MoO3(type-I) and WO3(type-II) with CdS plays a highly significant role in the co-catalytic activity.

Photoluminescence, antibacterial, X-ray/gamma ray absorption, supercapacitor and sensor applications of ZrTiO4 nanorods.

In the present communication, ZrTiO4 nanoparticles (NPs) are synthesized by the solution combustion method using urea (ZTOU) and oxalyl dihydrazide (ODH) (ZTODH) as fuel and calcined at 700 °C. The synthesized samples were characterized with different techniques. Powder X-ray diffraction studies show the presence of diffraction peaks corresponding to ZrTiO4. In addition to these peaks, a few additional peaks corresponding to the monoclinic and cubic phases of ZrO2 and the rutile phase of TiO2 are observed. The surface morphology of ZTOU and ZTODH consists of nanorods with different lengths. The TEM and HRTEM images confirm the formation of nanorods along with NPs, and the estimated crystallite size matches well with that of PXRD. The direct energy band gap was calculated using Wood and Tauc's relation and was found to be 2.7 and 3.2 eV for ZTOU and ZTODH respectively. The photoluminescence emission peaks (λ = 350 nm), CIE and CCT of ZTOU and ZTODH clearly confirm that the present nanophosphor might be a good nanophosphor material for blue or aqua green light emitting diodes. Furthermore, antibacterial activity and a viability test were conducted on two food borne pathogens. The X-ray/gamma ray absorption properties are also studied, which clearly show the ZrTiO4 might be a good absorbing material. Furthermore, cyclic voltammetry (CV) analysis of ZTOU nanorods shows very good redox peaks compared to that of ZTODH. From the electrochemical impedance spectroscopy (EIS) measurements, the charge-transfer resistances for prepared nanorods ZTOU and ZTODH are found to be 151.6 Ω, and 184.5 Ω respectively. The modified graphite electrode with ZTOU shows good sensing activity for both paracetamol and ascorbic acid, compared to ZTODH.

Green-engineered synthesis of Bi2Zr2O7 NPs: excellent performance on electrochemical sensor and sunlight-driven photocatalytic studies.

In this rapid growing eco-friendly research world, synthesis of non-toxic, highly effective photocatalyst for potential applications is necessary. Herein, a strong ability Bi2Zr2O7 nanoparticle (BZO NP) with pyrochlore structure was fabricated by solution combustion synthesis using green (Mentha spicata) and chemical (Glycine) fuels. The X-ray diffraction analysis confirms the formation of pure phase for synthesized BZO NP using pudina extract (BZOP NP) compared to BZO NP using Glycine fuel (BZOG NP). The lower energy band gap of synthesized BZOP NP was observed than BZOG NP and its values were found to be 2.26 and 2.49 eV measured by UV-visible absorbance spectral technique. The morphological analysis of pores and voids formation as examined by scanning electron microscopy (SEM) technique. The synthesized BZOP NP shows excellent photocatalytic activity for degradation of three different dyes under sunlight irradiation for about 150 min with 97.9% for Rose Bengal (RB) dye with lower charge transfer resistance (Rct) value. For the very first time, the synthesized NPs can be utilized as supercapacitor with good specific capacitance (SPCcv) value of 14.3 F/g and SPCGD (12.5 F/g) for BZOP compared to BZOG indicating pseudocapacitance nature. The synthesized nanoparticles (NPs) can sense lead nitrate and dextrose at concentration 1-5 mM in the potential range of - 1.0 to + 1.0 V. Accordingly, the reduction potential peak at - 0.25 V and oxidation potential peak found at - 0.82 V confirms the presence of lead content and presence of additional potential peaks at - 0.37 V and - 0.71 V for detection of dextrose biochemical. Recyclability experiment showed the retainment of photocatalytic activity up to five cycles indicating the photostability.

Synthesis of nano hydroxyapatite from Hypopthalmichthys molitrix (silver carp) bone waste by two different methods: a comparative biophysical and in vitro evaluation on osteoblast MG63 cell lines.

More than a thousand tonnes of fish bone wastes can be transformed into biomedical products annually. Alkaline hydrolysis and thermal calcification were used to create nanosized hydroxyapatite (HAp) crystals from Silver carp bone wastes. Biophysical tests were used to determine the nano size and chemical composition of synthesised hydroxyapatite. Alkaline hydrolysis hydroxyapatite (AH-HAp) was 58.3 nm, while Thermal calcination hydroxyapatite (TC-HAp) was 64.3 nm in size, confirmed by Atomic Force Microscopy. Energy Dispersive X-ray Analysis studies showed Ca/P (Calcium phosphate) ratio of AH-HAp to be 1.65, whereas TC-HAp as 1.45, confirming AH-HAp to be organically rich along with a similar Ca/P ratio as natural HAp. Fourier Transform Infrared Spectroscopy spectra indicated HAp formation from both procedures, however AH-HAp had superior crystallinity than TC-HAp confirmed from X-Ray Diffraction spectra. MG63 osteoblast cell lines showed 91% cell viability in cytotoxicity studies and 70.1% proliferation efficiency in Alkaline Phosphatase assay, which was higher than TC-HAp. The present study shows that HAp produced via alkaline hydrolysis has better biocompatibility which enhances its applicability as a biomaterial, than HAp synthesized through thermal calcination, which tends to incinerate organic moieties.

Carbon dots decorated cadmium sulphide heterojunction-nanospheres for the enhanced visible light driven photocatalytic dye degradation and hydrogen generation.

Carbon dots (C-dots) developed from beetroot is used for the rational design of cadmium sulphide based heterojunction photocatalysts (C-dots@CdS) using hydrothermal technique. The crystal structure, phase, morphology and optical characteristics of the synthesised materials are determined using X-ray diffraction (XRD), High resolution transmission electron microscopy (HR-TEM), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL spectroscopy), BET adsorption, X-ray photoelectron spectroscopy (XPS) and electrochemical studies. Using C-dots@CdS catalytic system, a superior photocatalytic activity relative to the undecorated CdS is observed. Among the C-dots@CdS samples, the CdS loaded with 6 wt% of C-dots exhibited enhanced hydrogen evolution rate compared with other samples considered for the study. CdS nanospheres modified with C-dots (6 wt%) resulted in the photocatalytic hydrogen evolution rate of 1582 µmolg-1 against 849 µmolg-1 evolution rate obtained for CdS nanospheres within 3 h. In spite of being 0D/0D type nano-heteroarchitecture, C-dots@CdS system obtained an apparent quantum yield of 6.37 % for the catalytic dosage of 20 mg under the irradiation of visible light. CdS in the C-dots@CdS system serves as the light harvester while C-dots with discernible edges can maintain the continuous supply of photo-excited charge carriers and hence can reduce the charge-carrier recombination. Further, the photodegradation of crystal violet dye using the optimised dosage of C-dots@CdS-6 exhibited an efficiency of 97.3 % in 120 min of visible light irradiation under neutral conditions. The detailed kinetic study reveals that the mechanism of photodegradation of crystal violet dye using C-dots@CdS system can be described using pseudo-second-order kinetics. The presence of oxygen rich hydrophilic surface functionalities of C-dots, the formation of near-surface heterojunction and the suitable band structure of C-dots@CdS system leading to the optimum charge carrier separation kinetics can be attributed to the enhanced photocatalytic performance. This work offers a promising strategy to develop bio-derived C-dots based heterojunction photocatalyst to address the burgeoning energy and environmental demands.

Carbon dots derived from Beta vulgaris: evaluation of its potential as antioxidant and anticancer agent.

Carbon dots (CDs) endowed with outstanding physico-chemical characteristics expeditiously garnered tremendous popularity in the scientific community. CDs can be synthesized from a variety of natural resources and can replace metal semiconductor quantum dots in the range of applications such as bio-imaging, sensing and catalysis. Herein, CDs are green synthesized fromBeta vulgarisvia a single step hydrothermal approach (b-CDs). The synthesized carbon dots are characterized using UV-visible spectrophotometry, Fluorescence spectroscopy, High resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction technique (XRD) and Raman spectroscopy. The b-CDs hence developed exhibited the signature 'excitation-dependent fluorescence emission' with its most intense emission in the green region. The quantum yield for the b-CDs obtained by this synthetic approach evinced an appreciable value of 11.6%. The antioxidant property of b-CDs are evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay to obtain a maximum scavenging activity of 94.5% at a concentration of 1000µg ml-1and its underlying mechanisms are illustrated. The blood compatibility of b-CDs are assessed using haemolysis assay and the cytotoxicity evaluated using MTT assay shows significant cell growth-inhibition against the human breast cancer (MCF-7) and hepatocellular carcinoma (HepG2) cell lines. This succinct study demonstrates the inherent therapeutic potential of biocompatible carbon dots.

'Luminescent carbon nanodots: Current prospects on synthesis, properties and sensing applications'.

'Nanocarbon science' ignited interest owing to its substantial scope in biomedicine, energy and environment-beneficial applications. Carbon dots (C-dots), a multi-faceted nanocarbon material, emerged as a homologue to graphene and henceforth geared extensive investigation both on its properties and applications. Eximious properties like excitation-wavelength tunable fluorescence emission, up-converted photoluminescence, photon-induced electron transfer, low cytotoxicity, chiroptical behavior, high chemical and photostability set the ground for astounding applications of carbon dots. Abundant availability of raw 'green' precursors complementary to other molecular/graphitic precursors make them environmentally benign, inexpensive and ultimately 'nanomaterials of the current decade'. This review focuses on the synthesis of carbon dots not only from natural sources but also from other carbonaceous precursors and contemplates the inherent but controversial properties. We also aim to garner the attention of readers to the recent progress achieved by C-dots in one of its prestantious area of applications as nanosensors.

Green Synthesized Luminescent Carbon Nanodots for the Sensing Application of Fe3+ Ions.

A single step hydrothermal mode of carbon nanodots (C-dots) synthesis from house-hold kitchen garbage such as snake gourd peel extract was successfully carried out. Characterisation of green synthesized C-dots were accomplished using UV-Visible and FTIR spectroscopy, Spectrofluorimetry and HRTEM. C-dots exhibited an appreciable quantum yield of 28.6%. Excitation-dependent photoluminescence emission properties and pH-sensitivity of C-dots were also studied in detail. C-dots exhibited strikingly selective detection of Fe3+ ions via fluorescence quenching mechanism. Linearity was obtained in a concentration range of 10-100 µM with detection limit of 0.398 µM in accordance with the Stern-Volmer relation. The existence of oxygen containing functional moieties in luminescent C-dots could be attributed to the effectual complexation between the metal ion and C-dots. The selective sensing property of C-dots towards Fe3+ ions provide avenue for biochemical analysis related to iron metabolism and diagnosis of anaemia.

Photoluminescence, TGA/DSC and photocatalytic activity studies of Dy3+ doped SrY2O4 nanophosphors.

Dy3+:SrY2O4 nanophosphors were prepared via a solution combustion method using glycine as an organic fuel. The structural, optical, and thermal properties of the nanophosphors were studied. Strain and crystal size were calculated via W-H analysis. The direct energy band gap is nearly 4.9 eV and photocatalytic studies reveal that Rh-B degradation of almost 50% can be achieved.

Green and Cost Effective Synthesis of Fluorescent Carbon Quantum Dots for Dopamine Detection.

Carbon quantum dots (CQDs) due to its high fluorescent output is evolving as novel sensing material and is considered as future building blocks for nano sensing devices. Hence, in this investigation we report microwave assisted preparation and multi sensing application of CQDs. The microwave derived CQDs are characterized by Dynamic Light Scattering (DLS) experiment and Fourier Infrared spectra (FTIR) to investigate the size distribution and chemical purity respectively. Fluorescent emission spectra recorded at varying pH shows varying fluorescence emission intensities. Further, emission spectra recorded at different temperatures shows that fluorescence emission of CQDs greatly depends on temperature. Therefore, we demonstrate the pH and temperature sensing characteristics of CQDs by fluorescence quenching behaviour. In addition, the interaction and sensing behaviour of CQDs for dopamine is also presented in this work with a detection limit of 0.2 mM. The steady state and time-resolved methods have been employed in fluorescence quenching methods for sensing dopamine through CQDs at room temperature. The bimolecular quenching rate constants for different concentration have been measured. The interaction between CQDs and dopamine indicates fluorescence quenching method is an elegant process for detecting dopamine through CQDs.

Novel metal-organic photocatalysts: synthesis, characterization and decomposition of organic dyes.

An efficient method for the photocatalytic degradation of methylene blue in an aqueous medium was developed using metal-organic complexes. Two novel complexes were synthesized using, Schiff base ligand, N'-[(E)-(4-ethylphenyl)methylidene]-4-hydroxybenzohydrazide (HL) and Ni(II) (Complex 1)/Co(II) (Complex 2) chloride respectively. These complexes were characterized using microanalysis, various spectral techniques. Spectral studies reveal that the complexes exhibit square planar geometry with ligand coordination through azomethine nitrogen and enolic oxygen. The effects of catalyst dosage, irradiation time and aqueous pH on the photocatalytic activity were studied systematically. The photocatalytic activity was found to be more efficient in the presence of Ni(II) complexes than the Co(II) complex. Possible mechanistic aspects were discussed.

Design and synthesis of metal complexes of (2E)-2-[(2E)-3-phenylprop-2-en-1-ylidene]hydrazinecarbothioamide and their photocatalytic degradation of methylene blue.

The photocatalytic degradation has been considered to be an efficient process for the degradation of organic pollutants, which are present in the effluents released by industries. The photocatalytic bleaching of cationic dye methylene blue was carried out spectrometrically on irradiation of UV light using Cu(II), Ni(II), and Co(II) complexes of (2E)-2-[(2E)-3-phenylprop-2-en-1-ylidene]hydrazinecarbothioamide (HL). The effects of pH and metal ion were studied on the efficiency of the reaction. Cu(II) complex shows better catalytic activity and the highest percentage degradation (~88.8%) of methylene blue was observed at pH 12. A tentative mechanism has also been proposed for the photocatalytic degradation of methylene blue.