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We present here a facile method for nonaqueous synthesis of highly crystalline nitrogen-doped carbon dots (N-CDs) via oligomerization of ethylene glycol while heating with β-alanine at 170 °C for 3...

Ever-degrading environment due to the application of a large amount of agrochemicals, like fertilizers into the soil, has raised the concern for implementing such measures which would not only reduce the chemical incorporation into the soil, but will also benefit the crops by shooting up the fertilizer utilization by the same. Henceforth, biodegradable formulations for phosphate are essentially required to undergird the evolution of modern day agriculture. Naturally occurring phosphate could not suffice the demands of global agriculture, and so, it has to be applied synthetically in the form of agrochemical. Taking the very facts into consideration, the preparation of a novel biodegradable formulation of nanocomposite hydrogel using PVA as polymeric matrix, kaolin clay as mechanical binder and DAhP as phosphate fertilizer is attempted in the present study. The analysis of final formulation was done using techniques like FT-IR, XRD and SEM. The synthesized compound is named PDK. It shows 66.6 g/g equilibrium swelling; shows 10 times swelling its own weight in 1 h of immersion and attained equilibrium after 3 h. Factors affecting swelling behavior like content of kaolin, temperature and pH have also been investigated which revealed that 1–3 wt% kaolin, 35–40 °C temperature and 6–7 pH are the best optimum conditions for PDK hydrogel to show best results in release and swelling. The release study for phosphate was done by volumetric ammonium phosphomolybdate method by dispersing the sample in water and soil and checking the release at an interval of 3 days for 30 days which revealed 88.8% release in water and 76.3% release in soil. The formulation shows considerable controlled release of DAhP and also presents a scope for the development of biodegradable phosphate-based controlled release fertilizer.

Detection of residual organic and inorganic species in water bodies, including drinking water, has led to developing strategies for their removal. Here, we report a very efficient method of removing Cr(VI), organic dye, and antibiotic from water using a type-II heterojunction based on Sn

Effective mitigation of polar organic impurities from industrial effluents is a global environmental challenge. Here, we describe the solvothermal synthesis of ammonia-functionalized graphene oxide (NH

Coal is primarily a fuel material but lately it has been utilized as an adsorbent for removing toxic metal ions. However, its usage for removing organic pollutants is not well studied. We report here a systematic study on the use of coal samples of varying carbon contents as adsorbents for removing Basic Blue 41 as a model cationic dye. The coal samples were collected from coal mines and were thoroughly characterized. The concentrations of carbon, hydrogen, oxygen, nitrogen and sulphur contents were measured by CHNS analyzer. The concentrations of aluminum, silicon, sulphur, titanium and iron were determined by EDXRF, which corresponded to silicon dioxide (quartz) and aluminium silicate (kaolinite) as the major mineral inclusions, corroborated by XRD results and micrographs showing elemental maps determined from SEM-EDAX. The coal samples with low carbon content revealed higher adsorption capacity (qe ∼ 8.0–9.3 mg/g) of Basic Blue dye at optimized adsorbent dose (2 mg/mL), pH 9 and contact time (120 min). The adsorption kinetic studies satisfied pseudo second order model and the intra-particle diffusion of the dye was evident. The dye adsorption followed Langmuir adsorption isotherm, and the qmax values ranged between 17 and 30 mg/g for low carbon content coal. The FT-IR, Brunauer-Emmett-Teller (BET) surface area and zeta potential results of the coal samples could explain the adsorption phenomenon of cationic dye. The kinetic and thermodynamic studies revealed that the adsorption of Basic Blue 41 dye was based on chemisorptions mechanism.

Graphene oxide reduced by adenosine 5′-monophosphate (RGO-AMP) has been developed as a smart nanoscale adsorbent for unprecedented high removal of uranyl ions from aqueous medium. The amine/amide and phosphate groups of AMP are grafted in the graphene oxide structure by reducing the carboxylic acid groups of GO to facilitate a stronger affinity for interaction with uranyl ions. An array of characterization techniques, e.g., Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), zeta potential and BET surface area measurements confirmed the functionalization of graphene oxide by AMP. The uranyl ion adsorption on RGO-AMP was qualitatively revealed from 2D elemental mapping recorded by field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray analysis (EDX) and by XPS analysis. The quantitative estimation of uranyl ion adsorption on RGO-AMP was done by inductively coupled plasma optical emission spectroscopy (ICP-OES). The adsorption followed a pseudo second order kinetic model and Langmuir adsorption isotherm, which revealed an adsorption capacity (qmax) of 3024 mg g−1 corresponding to 93% removal of uranyl ions in 240 s at an optimized adsorbent dose of 5 mg per 100 mL adsorbate solution taken at pH 6. Such high uranyl ion adsorption is attributed to the chelation of uranyl ions with the phosphate oxygen and with the aromatic nitrogen of the purine residue of AMP. This method exhibited high uranyl ion selectivity in the presence of interfering cations, viz. Al3+, Cd2+, Co2+, Cu2+, Fe2+, Hg2+, Pb2+, Mn2+, Zn2+, and Ni2+. The uranyl ion adsorption was thermodynamically favourable, spontaneous and endothermic in nature, while the XPS studies highlighted a probable adsorption mechanism. The sustainability of RGO-AMP as an adsorbent has been demonstrated by showing the regeneration and re-usability of the adsorbent for 5 cycles.

Low grade coals with high sulphur contents are not suitable as fuels in thermal power plants due to generation of high ash content and emission of toxic sulphur oxide gases. Here we have demonstrated an alternate use of pyrite rich coal as a source for sustainable generation of hydrogen peroxide and hydroxyl radicals in aqueous medium via solar light induced photo-Fenton process which were utilized for degradation of toxic azo-dyes. The textural, compositional and morphological features of pristine pyritic coals with varying sulphur concentrations are studied by an array of characterization techniques. The dye degradation capacities of pyrite rich coal are studied using model dye solutions e.g., Basic Blue 41 containing single azo group per unit and Trypan Blue containing two azo groups per unit. The rate of degradation (k) is faster for Basic Blue-41 (0.0192 min−1, ∼99% degradation) at optimized solar radiation exposure time, pH 6 and dose of 1 g/L pyritic coal. The dye degradation is presented as a measure of solar radiation accumulation energy per unit volume, and it is attributed to in-situ generation of hydrogen peroxide and hydroxyl radicals, and re-confirmed from scavenging studies. The dye degradation mechanism by pyritic coal is discussed in the light of solar photo-Fenton mechanism with respect to (1) qualitative identification of trace quantities of degradation products by gas chromatography-mass spectrometry technique; (2) leaching of 2700 mg/L iron in the reaction medium, estimated by inductive coupled plasma optical emission spectrometry, and (3) and changes in the chemical speciation of iron, sulphur and oxygen in the used coal by X-ray photoelectron spectroscopy.

Phthalic acid esters or phthalates in wastewater are priority pollutants and demand efficient method for remediation. Here we present a novel utilization of low grade coal, which is otherwise a waste, modified by chitosan as adsorbent for removal of diethyl phthalate (DEP) via adsorption. A low carbon and high silicate content coal was chosen, characterized by CHN analyzer, energy dispersive X-ray analysis and by X-ray diffraction. A composite of mineral rich coal and chitosan is prepared via electrostatic interaction and hydrogen bonding between the hydroxyl groups of chitosan and the silicate group of coal; confirmed by Fourier transformed infrared spectroscopy, thermogravimetry analysis and zeta potential measurements. An optimized 9:1 weight ratio of coal-chitosan composite exhibited a positive zeta potential value in aqueous medium and corresponded to 91.1% DEP adsorption at an optimized condition e.g., pH 5.8, adsorbent dose of 4 mg/mL and contact time of 4 h. The adsorption is thermodynamically favorable and followed pseudo-second order kinetics, and attributable to chemisorption process, is attributed to electrostatic interaction and hydrogen bonding between the DEP and the functional groups in the composite. The adsorption isotherm data was best fitted non-linearly by Sips isotherm model, which is consistent with Freundlich adsorption isotherm for lower concentration of DEP (5 to 100 mg/L), while Langmuir adsorption was favored for adsorption of higher DEP concentrations (100 to 400 mg/L). The qmax was 42.67 mg/g, which is a significant improvement in DEP sorption from aqueous medium among the readily degradable adsorbents reported so far. The practical application of coal-chitosan composite as adsorbent has been demonstrated by its re-usability and ability for sorption of DEP from spiked municipal wastewater, supported by decrease in chemical oxygen demand value of treated wastewater.

Brominated aromatic compounds including bromophenols are hazardous and are being fast recognized as priority pollutants. We present here a novel photo-Fenton based degradation system using selenium doped copper oxide nanoparticles (Se-doped CuO NPs)/H2O2/UV, which facilitated 99.5% degradation of 4-bromophenol in 90 min at a rate of 0.057 min−1. The Se-doped CuO NPs are prepared by precipitation method, and their structural, morphological and optical properties are characterized. The selenium doping is chosen owing to its favorable photo-absorption property and its doping in CuO NPs improved charge transfer properties and resulted in enhanced in-situ generation of hydroxyl radicals. The selenium doping also restricted the growth of CuO crystals, due to which the surface area of the nanoparticles increased and led to higher rate of photochemical reaction. The degradation profile is measured by high performance liquid chromatography method. The photo-Fenton process is initiated by extraneous H2O2 and the reaction is sustained by the in-situ generation of hydroxyl radicals, as demonstrated from the ROS scavenger studies. The de-bromination, formation of 4-benozoquinone as an intermediate degradation product and production of anionic species in residual solution after degradation due to cleavage of the molecular structure of 4-bromophenol are the key events confirmed by ion chromatography and gas chromatography coupled with mass spectrometry studies. The robustness of the Se-doped CuO NPs as catalyst has been confirmed from the re-usability studies for seven cycles.

Here we present a simple yet efficient analytical method for sensing ultratrace levels of Hg2+ ions by highly water soluble CdS quantum dots functionalized with thiourea as a probe. The bluish photoluminescence emission of the probe responded to a systematic linear photoluminescence quenching in the presence of increasing concentration of Hg2+ ions. The photoluminescence quenching by Hg2+ ions was attributed to agglomeration of the quantum dots, which has been confirmed by zeta potential measurements. The sensitivity (31.38 L/mg) and LoD (0.11 μg/L) of Hg2+ ion detection by our method are two folds improved with respect to the existing data of CdS as sensor. The improved detection is attributable to synthesis of less than 3 nm diameter CdS quantum dots which rendered very high water solubility and hence facilitated better interaction with Hg2+ ions. The detection of Hg2+ ion was free from most interfering cations and anions, except for minor interference from Cu2+ and Pb2+ corresponding their concentrations expected in ground water. Further, the scope for visual detection of Hg2+ was explored, which revealed naked eye recognizable photoluminescence quenching of the probe treated 0.3 mg/L of Hg2+ ion when excited by a light source of 365 nm. The suitability of our probe to analyze Hg2+ in real samples has been demonstrated by Hg2+ spike analysis in groundwater and river water samples.

The presence of phenolic compounds in petroleum refinery wastewater is a matter of significant environmental concern. Its removal is achieved through various methods, among which adsorption is an efficient and economically viable option. This study reports the development of activated biochar (EABC) from Eucalyptus wood pyrolytic biochar (EPBC) to remove phenols from petroleum refinery wastewater. The best activation strategy involved ball-milling of KOH and EPBC in the ratio 3:1, followed by annealing at 800 °C under an N2 atmosphere. The activated biochar (EABC-3–800) exhibited high phenol adsorption capacity (308.9 mg/g), attributed to the presence of heterogeneous pores, corroborated by large BET surface area (2048 m2 /g). As determined through HPLC, the EABC-3–800 could remove nearly 95% phenol (C0=114 ppm) from the wastewater of the delayed coking unit of a petroleum refinery. The best-fitting of the adsorption results in the Freundlich isotherm model substantiates the hypothesis of pore-based adsorption of phenol compared to the surface-adsorption-based Langmuir isotherm. The phenol adsorption kinetics followed the pseudo-second-order model, indicating weak chemical interactions between phenol and activated biochar. The regeneration and reuse of EABC-3–800 for a minimum of five operational cycles demonstrate its potential for industrial wastewater remediation.

BACKGROUND Cardiovascular Disease (CVD) is the largest single contributor to global morbidity and mortality in the adult population and will continue to dominate the trends in the future. The aim of the study is to find out the association of Body Mass Index (BMI) with some of the risk factors of cardiovascular disease. MATERIALS AND METHODS A community-based cross-sectional study was conducted in the urban slums of Dibrugarh, to find the association of BMI with some of the risk factors of cardiovascular disease in the adult population of 45 years and above living in the urban slums of Dibrugarh. This study was conducted among 208 subjects from May 2015-October 2015. Each study subject was interviewed on sociodemographic variables with the help of a pretested questionnaire. The blood pressure of participants was measured following the standard operation procedures as laid down by the WHO. Height, weight, waist circumference and hip circumference were measured. Data were analysed by use of percentage and Chi-square tests. RESULTS The overall prevalence of hypertension and diabetes from history and medical records was 46.63% and 14.90%, respectively. Hypertension was predominant in females 50 (46.3%) than males 43 (43%), while diabetes was predominant among males 18% (18) than females 12.04% (13). A 33.17% of the study participants had a BMI of 18.5-22.9. Abnormal waist-hip ratio (>0.9 cm in males) was observed in 76% and (>0.85 cm in females) was observed in 75.93%, respectively. A statistical significance exists between WHR and BMI in both males (p

The affinity of uranyl ions for binding with nitrogen bearing ligands has led to development of several amine/amide reduced graphene oxides as adsorbent for uranyl ion removal. We have developed a novel nano-adsorbent (referred as CARGO) with an aim of increasing nitrogen groups in reduced graphene oxide (GO) for enhanced uranyl ion removal. There are two important stages in this work: (a) synthesis of CARGO, which comprises of GO reduction by the as synthesized l -cysteine amide and (b) optimization of uranyl ion adsorption by CARGO. The synthesis of l -cysteine amide (precursor) is confirmed by FT-IR and 1 H NMR. Reduction of GO by l -cysteine amide is revealed from decrease in the acidic functionalities of GO and characterized by XRD, UV-vis, Raman and FT-IR spectroscopy techniques. The FE-SEM and TEM studies CARGO revealed flake like morphology. The uranyl ion adsorption on CARGO surface was confirmed from EDX analysis and supported by two dimensional elemental maps of uranium and carbon. The regeneration, re-usability and selectivity of uranium adsorption by CARGO have been studied. The uranyl adsorption was kinetically and thermodynamically favorable, which accounted for 88.9% uranyl ion removal in 60 min at an optimized pH 5 via chemisorption mechanism and the corresponding q max derived from Langmuir adsorption isotherm was 337.93 mg/g. Such high uranyl ion adsorption capacity is attributed to more amine and/or amide binding sites on CARGO, high BET surface area (57.086 m 2 /g) and negative zeta potential values of the adsorbent.

There has been consistent effort on manipulating surface properties of ZnO NPs to produce higher concentration of reactive oxygen species (ROS) to enhance sustained photocatalytic degradation. Here we present a very simple strategy of synthesizing nanocomposites of ZnO NPs and ammonia modified graphene oxide (ZG) as an efficient photocatalyst for enhanced ROS generation and degradation of trypan blue azo dye and 4-nirophenol. The batch of photocatalyst made of ZnO NPs and 5 wt% ammonia modified graphene oxide (ZG5) has been well characterized and its stability in aqueous medium is confirmed from minimal zinc leaching. The photocatalytic degradation of the dye and 4-nitrophenol followed Langmuir-Hinshelwood kinetics model. At optimized conditions, i.e., NH3 concentration for modifying graphene oxide, photocatalyst dose (ZG5), pH of the medium and contact time, the rate of photocatalytic degradation of trypan blue (k = 7.3 × 10−3 min−1) and 4-nitrophenol (k = 5.5 × 10−3 min−1), were more than 7–10 folds higher than that of pristine ZnO NPs. The enhanced rate of photocatalytic degradation by the ZG5 nanocomposite was correlated with higher ROS generation, owing to diffusion of photoexcited electrons and holes to the surface of the nanocomposite via conducting reduced graphene oxide to favour ROS generation. The ROS scavenger studies confirmed in-situ generation of superoxide radicals, hydroxyl radicals and singlet oxygen in the reaction medium. The degradation pathway for 4-nitrophenol has been proposed via formation of 1,4-benzoquinone as revealed from HPLC studies. The GC–MS studies confirmed nearly complete mineralization of the dye and 4-nitrophenol without formation of any by-product.

We present here a simple thermal route for synthesizing 5.1 wt% cobalt doped CuO nanoparticles (NPs) as the optimized composition of the best heterogeneous CuO catalyst for catalytic reduction of toxic 4-nitrophenol to industrially beneficial 4-aminophenol. The reduction is completed in merely 3 min in the presence of 8 mM NaBH4 as reducing agent. The optimized catalyst dose was 2 mg/L for converting 0.12 mM 4-nitrophenol and the corresponding rate constant (k) for reduction reaction was 43.8 × 10−3 s−1 per mg of catalyst. The catalytic reduction reaction was monitored by UV–vis spectroscopy method and by HPLC analysis. The mechanism is discussed in the light of hydride transfer phenomenon facilitated by large surface area and positive surface charge of the cobalt doped CuO nanoparticles. The cobalt doping resulted in: (a) increasing surface area due to decrease in particle size of the CuO NPs to 10 nm, measured by HRTEM; (b) improve stability of the cobalt doped CuO NPs. The cobalt dopant occupied the grain boundaries of CuO to reduce the particle size as derived from positron annihilation lifetime spectroscopy. The X-ray photoelectron spectroscopy analysis of unused catalyst and the spent catalyst revealed occurrence of Co2+ and Co3+ states at the surface. While the X-ray diffraction studies of spent catalyst confirmed the inhibition of reduction of the surface CuO to metallic copper in the presence of NaBH4, attributable to cobalt doping. It was concluded that cobalt doping led to stable and efficient CuO NPs as catalyst for reduction reaction.

Presented here is a simple yet rapid and efficient analytical method for visual as well as spectroscopic method for sensing of trace concentrations of Cu2+ ions in aqueous medium by systematic photoluminescence quenching of a highly water soluble probe made of CdS quantum dots surface modified by thiourea. The salient features of this work describe rapid detection (2 min equilibration time) of Cu2+ ions at wider linear concentration range (0.025 - 10 mg/L) corresponding to a sensitivity of 2.81(mg/L)-1 and limit of quantification of 47.3 μg/L, respectively, suitable for Cu2+ sensing in drinking water and ground water. Further, the detection of Cu2+ ion was free from most interfering cations and anions, except for minor interference from Cr3+, Hg2+ and Pb2+. The robustness of our probe for Cu2+ sensing is demonstrated from efficient Cu2+ spike recovery analysis in groundwater and river water samples.

Adsorption is considered to be one of the most efficient and cost-effective processes for the removal of pollutants including dyes from polluted water bodies. Wide range of materials is being studied for removing dye molecules that impart colour to water. Chitosan has emerged as a low-cost, non-toxic, biodegradable and easily available option for removing dye molecules by adsorption. The functional groups in chitosan, e.g. the hydroxyl and the amino groups, are responsible for the adsorption of cationic as well as anionic dyes. Here we have discussed some of the significant cases of cationic and anionic dye adsorption by chitosan. Broadly, chitosan-based adsorbent can be categorized as (a) grafted and cross-linked chitosan to enhance adsorption capacity and also to impart superior mechanical stability so that the adsorbent can be used in harsh condition and (b) composites with wide range of materials, e.g. clay, carbon materials, other polymers and metal oxides. Further sizes and morphologies, e.g. sphere, beads, nanofibres, have effects on the adsorption capacities. In addition, the scope for adsorptive photocatalytic dye degradation has been discussed. For this purpose, ZnO–chitosan nanocomposite is taken as a model adsorbent cum photocatalyst for removing Congo red anionic dye, where chitosan facilitated adsorption while ZnO favoured dye degradation.

Here we have demonstrated a methodology for detecting nickel ions in aqueous medium using photoluminescence (PL) lifetime of the probe made of glutathione capped CdTe/CdS core-shell quantum dots. The ratio of (τavg)probe/(τavg)probe+Ni2+ has been developed as an analytical signal for detecting Ni2+ ions. The plot of (τavg)probe/(τavg)probe+Ni2+ versus concentration of Ni2+ revealed a linear positive slope and the sensitivity was 0.61 L/mg, which is in good agreement with that determined from conventional Stern-Volmer plot (i.e., 0.64 L/mg). The limit of Ni2+ detection was 23 μg/L. The temperature dependent steady state PL quenching, time-resolved PL decay and photocatalytic dye degradation in absence and in presence of Ni2+ suggested that the PL quenching by Ni2+ is due to pure collision based dynamic quenching with favourable electron transfer process. On the other hand, the present method was not applicable for Cu2+ detection as the ratio of (τavg)probe/(τavg)probe+Cu2+ was non-responsive over the given range of Cu2+ concentration. The PL quenching by Cu2+ comprised of a combination of dynamic quenching and due to interaction of Cu2+ with the probe. It has been concluded that ratio of (τavg)probe/(τavg)probe+analyte can be a promising analytical signal for detecting metal ions, particularly for those exhibiting dynamic PL quenching.

A rapid and simple aqueous method has been developed for synthesizing CdTe/CdS core shell quantum dots (QDs) by refluxing glutathione (GSH) with Cd2+ and Te2− precursors at 100 °C without using inert medium. Here GSH has dual role, i.e., as an in-situ source of sulphide for deposition of CdS on CdTe and as a capping agent to stabilize the CdTe/CdS QDs. As the refluxing time was enhanced from 15 min to 105 min, the sizes of the spherical shaped CdTe/CdS QDs increased from 2.8 ± 0.8 nm to 3.9 ± 1.1 nm, the crystalline nature improved, GSH capping content decreased and the CdS shell deposition was increased. The size dependent change in photoluminescence (PL) from green to red was observed. The photoluminescence quantum yield (PLQY) was improved with refluxing time and maximum PLQY was obtained for the batch synthesized by 60 min refluxing. The PL of these QDs were drastically quenched by ppb levels of Cu2+ ions. Instead of the batch with maximum PLQY, the best Cu2+ sensitivity and selectivity was obtained for the batch synthesized by refluxing for 30 min. This is due to optimal GSH capping content required for availability of Cu2+ ions at the surface of the QDs for favorable electron transfer process, confirmed by PL decay kinetic studies.

We report methodology for developing three different surface modified biochars produced from rice straw, bagasse, and eucalyptus wood for the adsorptive removal of benzoic acid as a model pollutant for remediation of naphthenic acid-rich petroleum refinery wastewater. Solid-phase extraction or miniaturized column format packed with (a) untreated biochars; (b) acid-treated (HCl and HNO3) biochars; and (c) non-covalent PDDA (cationic polyelectrolyte) wrapped biochars were employed for the adsorption studies. The benzoic acid loading capacities were in the range of 0.46 and 7.97 mg g−1, with an order of loading as: HCl-treated > HNO3-treated > PDDA-treated > untreated biochar. The acid-treated biochars revealed an increase in the oxygen content (wt %) owing to –COOH groups, corroborated by FTIR studies and point of zero charges (pHzpc) = 2.40. The best loading result, attributed to dipole-based or π-π stacking, was obtained for HCl-treated rice straw biochars. Its BET surface area increased from 18.45 m2 g−1 (untreated) to 49.01 m2 g−1 HCl-treated, with pore volume (0.067 cm3 g−1) and pore diameter (55.27 A), corroborated by observation of pores of different sizes and patterns by scanning electron microscopy. The optimum pH for maximum adsorption of benzoic acid was 2, and 3 mL methanol was used to regenerate the biochar column with up to 90% removal of the adsorbate. Validation of experimental parameters was performed through naphthenic acid spiked water, and the results were also compared with adsorption over activated carbon. Our results are optimistic towards developing biochars as a low-cost and eco-friendly option to manage agricultural waste for removing pollutants from water.

Structural modification of semiconductor type nanoparticles by doping with metals and non-metals renders versatility of the material. Here, we report the synthesis of

Surface defects are potential sites for modifying the activities of photoexcited electrons and holes, and may consequently affect photocatalytic activity. Here we have demonstrated how surface defects in copper oxide nanoparticles can be engineered by electron rich capping agent (like TPPO) to drastically improve the rate of photocatalytic degradation of rhodamine B dye. The steady state photoluminescence spectroscopy indicated metal vacancies and cluster vacancy defects in the as synthesized batches of bare, PVP (polyvinylpyrrolidone) capped and TPPO (triphenylphosphine oxide) capped copper oxide nanoparticles (NPs). The positron annihilation lifetime spectroscopy studies confirmed that these electron deficient defects were mainly located at the grain boundaries. As compared to the bare and the PVP capped CuO NPs, the positron lifetime parameter ‘τ1’ for TPPO capped CuO NPs was significantly small, which is due to faster annihilation of positrons trapped in free volume defect sites by the local electrons. Unlike PVP, the electron rich TPPO is capable of transporting more electrons to the electron deficient defect sites, due to which the rate of photocatalytic dye degradation was three to four folds higher for the TPPO capped CuO NPs (k = 0.556 h−1) than polyvinylpyrrolidone (PVP) capped CuO NPs (k = 0.168 h−1) and bare CuO NPs (k = 0.143 h−1). The reduced rate of photocatalytic dye degradation for bare and PVP capped CuO NPs were attributable to trapping of photoexcited electrons at the defect sites. The photocatalytic dye degradation was associated with generation of hydroxyl radicals and H2O2 species. The maximum photocatalytic dye degradation by TPPO capped CuO NPs was corroborated with highest concentration of H2O2 detection (125 μM), followed by 79 μM for PVP capped CuO NPs and 65 μM for bare CuO NPs. A detailed mechanism of the role of defects in photocatalytic process has been outlined.

A facile one pot method has been developed for synthesis of stable (ξ = −37.5 mV), orthorhombic structured SnS nanorods capped with mercaptoacetic acid by precipitation method. The SnS nanorods were measured to be about 45 nm long with a diameter of 20 nm, as studied by transmission electron microscopy (TEM). The band gap of the MAA capped SnS nanorods was 1.81 eV, measured by diffused reflectance spectroscopy and was larger than the bulk SnS. The relative positions of highest valence band and lowest conduction band were determined from theoretical band structure calculation as 1.58 eV and −0.23 eV, respectively. The UV–Visible–NIR fluorescence emission spectrum of the SnS nanorods revealed intense emission peak at 1000 nm (1.239 eV) and weaker peaks at 935 nm, 1080 nm, 1160 nm which is likely to be due to Sn2+ vacancies. The as-synthesized SnS nanorods exhibited more than 95% sunlight induced photocatalytic degradation of trypan blue in 4 h, following first order kinetics with high rate of degradation (k) (0.0124 min−1). The observed dye degradation is attributable to generation of reactive oxygen species (ROS), confirmed from terephthalic acid assay. The ROS generation has been explained on the basis of interaction between photoexcited electrons from conduction band with molecular oxygen adhered to the surface of nanorods owing to favourable redox potentials of O2/O2 − (−0.20 eV) in normal hydrogen electrode (NHE) scale.

Copper oxide thin film of about 260–280 nm thickness was deposited using pulsed laser deposition (PLD) on glass substrate at 350 °C and post depositional sample treatment was performed by ion implantation with 50 keV N 5+ ion beam with varying particle fluence. Amorphous copper oxide thin film deposited at 80 mTorr partial pressure of oxygen was transformed to cubic Cu 2 O phase (20.2 nm) when implanted at 1 × 10 16 particles/cm 2 . While mixed Cu 2 O and CuO phases in the thin film deposited at 100 mTorr oxygen pressure was transformed to single phase of Cu 2 O (23.5 nm), with enhanced crystallinity when implanted with 2.5 × 10 15 particles/cm 2 . The phase transformation and improved crystallinity is attributed to thermal effect owing to stopping of incident ion beam. Implantation with higher particle fluence led to transformation to CuO phase with reduced crystallite sized and the increased electrical conductivity.

Mercury is extremely toxic to the environment and is detrimental to human health. We describe here the development of an analytical method comprising mercaptoacetic acid capped CdS quantum dots (QDs) immobilized on calcium alginate microbeads (referred here as CA@CdS) for rapid, selective and quantitative detection of Hg2+ ions based on a fluorescence quenching phenomenon. The feasibility of detecting Hg2+ ions in this method is extended to real time analysis by spiking 0.5 mg L−1 and 1.0 mg L−1 Hg2+ ions in batches of municipal tap water. The mechanism of fluorescence quenching has been explained on the basis of adsorption of Hg2+ (adsorption capacity was determined to be 88.33 μg g−1). The selectivity of Hg2+ ions is attributable to its soft acid–soft base interaction between Hg2+ and the sulphydryl group of the mercaptoacetic acid capped CdS QDs. The fluorescence quenching phenomenon satisfied the Stern–Volmer equation and was linearly correlated with Hg2+ ions concentrations in the range of 0.015 and 2.0 mg L−1. The limit of detection of Hg2+ ion was determined to be 0.008 mg L−1 at an optimized condition, i.e., pH 6 and contact time 30 min; and the detection was not affected by other experimentally relevant cations like Na+, Mg2+, K+, Ca2+, Mn2+, Fe2+, Cu2+, Pb2+, Cr3+, Zn2+, As3+, Cd2+; and anions like Cl−, CO32−, HCO3−, HPO4−, SeO4−, SO42−. The major advantage of this nano-fluoroprobe is that it can detect as well as remove Hg2+ ions from an aqueous medium. The fluoroprobe can be recovered and re-used for subsequent cycles of detection and removal of Hg2+ ions.

Highly stable copper oxide (CuO) nanoparticles are synthesized by a precipitation method and stabilized by in situ capping with triphenylphosphine oxide (TPPO). The as-synthesized CuO nanoparticles were characterized for average particle size (8 nm) by transmission electron micrography (TEM); an optical band gap of 2.29 eV by diffused reflectance spectroscopy and a large BET surface area (105.82 m2 g−1). The sunlight induced photocatalytic activity towards the degradation of acid orange 74 (an azo dye) by TPPO capped CuO nanoparticles was attributed to unfavorable electron capturing by molecular oxygen to produce reactive oxygen species. This is demonstrated from theoretical band structure calculations which revealed valence band edge (2.59 eV) and conduction band edge (0.29 eV) for TPPO capped CuO nanoparticles, which are unfavourable for electron transfer with respect to the redox potentials of O2/O2˙− (−0.2 eV) and H2O/˙OH (2.2 eV) in the NHE scale. Strikingly, TPPO capped CuO nanoparticles when mixed with 5 mM K2S2O8 exhibited 99% degradation of acid orange-74 in 180 min under sunlight exposure. A similar dye degradation efficiency was observed when CuO nanoparticles were mixed with H2O2 in the reaction medium. The mechanism for the drastic improvement in the dye degradation due to the addition of K2S2O8 or H2O2 has been explained on the basis of favorable redox couples of S2O82−/SO4˙− (2.01 eV) and H2O2/˙OH (0.87 eV) which could accept photoexcited electrons from the conduction band of CuO to produce reactive hydroxyl radical species. Using selective scavenger for reactive oxygen species, the generation of O2˙− was ruled out and hydroxyl radicals were confirmed as the major reactive oxygen species for the degradation of acid orange-74 dye. Ion chromatography studies of the aliquot left after sunlight induced photocatalytic dye degradation revealed anions, viz. nitrate, sulphate, oxalate and formate, which are released due to mineralization of the dye solution by a photocatalytic process. The performance of the photocatalytic dye degradation was unchanged for 5 repetitive catalytic cycles and hence it was concluded that TPPO capped CuO nanoparticles offer excellent photocatalytic dye degradation ability when suitable electron capturing agents like potassium persulphate are used in tandem.

In this study we present quantitative elemental analysis techniques like energy dispersive X-ray fluorescence analysis and instrumental neutron activation analysis to assess the impact of industrial discharge on environment. Two cases are discussed, i.e., (a) enrichment of zinc levels in the soil (1080 ± 76 mg kg−1) and zinc uptake ranging between 628 and 40 mg kg−1 in edible plants and cereals grown in agricultural fields near an active zinc smelter, Rajasthan; (b) depth-wise distribution of Cr, Pb and other metals in the sediment core samples from Sundarban wetland, West Bengal, indicating waste discharge from tanneries and other industries.

ZnS nanoparticles implanted with 45 keV O5+ ion beam exhibited 83.6 % degradation of methyl blue in 2 h. This idea was utilized to fabricate nanocomposite system of ZnS and PMMA where ZnS nanoparticles were immobilized in PMMA film and irradiated with 45 keV O5+ ion beam at particle fluence of 2.5 × 1015, 1 × 1016 and 4 × 1016 particles/cm2. These irradiated batches of ZnS nanoparticle immobilized in PMMA batches revealed formation of porous structure characterized by scanning electron microscopy and these batches exhibited 54 % photocatalytic degradation of methyl blue in 80 min which was higher as compared to the pristine ZnS nanoparticles.

The total metal concentration and bioaccessible concentration of Cr, Mn, Fe, Cu, Zn, Se in Momordica charantia, Asparagus racemosus, Terminalia arjuna and Syzyzium cumini were measured by instrumental neutron activation analysis and by inductively coupled plasma mass spectrometry analysis (ICP-MS). The bioaccessible concentrations were determined in the gastrointestinal digest obtained after treating dried powdered samples sequentially in gastric and intestinal fluid of porcine origin at physiological conditions. The bioaccessible concentration of Fe was in the range of 58–67 mg kg−1, Mn was 10.2–14.6 mg kg−1, Cu was 3.7–4.8 mg kg−1 and Zn was 10.6–18.4 mg kg−1, were within the safety limits set for vegetable food stuff set by Joint FAO/WHO. The bioaccessibility of Zn, an essential element, was high (40–50 %) in M. charantia and in S. cumini. In addition, the total metal contents and bioaccessible concentration of Ni, Se, Cd and Pb in these samples were measured by ICP-MS. The total Cd content in S. cumini (2.6 ± 0.2 mg kg−1) and its bioaccessible concentration (0.6 mg kg−1) were strikingly high as compared to the other samples. Though total Hg contents were determined by ICP-MS, but their bioaccessible concentrations were below the detection limit (0.036 mg kg−1).

Selenium doped ZnO nanoparticles synthesized by mechanochemical method were spherically shaped of size distribution of 10.2 ± 3.4 nm measured by transmission electron microscopy. Diffused reflectance spectroscopy revealed increase in the band gap, ranging between 3.47 eV and 3.63 eV due to Se doping in ZnO nanoparticles. The antibacterial activity of pristine and Se doped ZnO nanoparticles was attributed to ROS (reactive oxygen species) generation in culture media confirmed by TBARS assay. Compared to complete inhibition of growth by 0.45 mg/mL of pristine ZnO nanoparticles, the batches of 0.45 mg/mL of selenium doped ZnO nanoparticles exhibited only 51% inhibition of growth of Escherichia coli . The reduced antibacterial activity of selenium doped ZnO nanoparticles was attributed to two opposing factors, e.g., ROS generation for inhibition of growth, countered by sustaining growth of E. coli due to availability of Se micronutrients in culture media, confirmed by inductively coupled plasma mass spectrometer measurement. Higher ROS generation by selenium doped ZnO nanoparticles was attributed to creation of oxygen vacancies, confirmed from green emission peak observed at 565 nm. The impact of higher ROS generation by selenium doped ZnO nanoparticles was evident from enhanced photocatalytic degradation of trypan blue dye, than pristine ZnO nanoparticles.

Semiconductor nanoparticles (NPs) have attracted much attention as a new class of fluorescent probe for many biological applications including biosensors for glucose, cholesterol, cysteine etc., which were based on their size dependent unique electrical and photophysical properties. One of the major challenges in fabricating nanomaterial based biosensor is conjugation of a suitable compound to quantum dots which is preferably selective to the analyte of interest. Here we report our studies on synthesis, characterization and application of jack bean meal urease immobilized on CdS quantum dots (QDs) for sensing of urea. The CdS QDs were synthesized by chemical precipitation method using Mercaptoacetic acid (MAA) for controlling size as well as for imparting functional group for conjugating urease. The urease immobilize on MAA capped CdS nanoparticle was characterized by an array of techniques, like, UV- visible, Fluorescence, XRD, FT-IR and SEM EDAX. The detection capability of urea was studied by fluorescence spectroscopy at an excitation wavelength of λex = 430 nm and emission wavelength of λem= 546 nm. This method was capable to detect urea in the concentration range of 0.1 µM to 1 mM. Copyright © 2013 VBRI press.

Se doped ZnO nanoparticles (NPs) were successfully synthesized by thermo-mechanical method whose band gap increased with concentration of Se doping. Transmission electron microscopy of 5 wt% Se doped ZnO NPs revealed spherical nanoparticles of average size of 9.5 nm. X-ray photoelectron spectroscopy (XPS) revealed Se 3d binding energy at 59.5 eV, confirmed SeO2 in the doped ZnO NPs. Fluorescence emission spectroscopy of Se doped ZnO NPs revealed oxygen vacancies which increased with the concentration of Se doping. The photodegradation efficiency of trypan blue (TB) using 30 W UV lamp was higher for Se doped ZnO NPs than pristine ZnO NPs, depended on Se doping concentrations, UV illumination, concentrations of photocatalyst and pH of the dye solution. The batch of 0.6 mg of 5 wt% Se doped in ZnO NPs per mL of TB dye maintained at pH 5 exhibited maximum photodegradation efficiency (89.2 ± 3.1%). Higher photocatalytic degradation efficiency for Se doped ZnO NPs was correlated with incorporation of oxygen vacancies due to Se doping, which were likely intermediate levels for transiting photoexcited charge carriers for generation of hydroxyl radicals and consequently facilitated photodegradation. Terephthalic acid assay confirmed formation of hydroxyl radicals in dye solution treated with photocatalyst.

Detection of ultratrace levels of aqueous uranyl ions without using sophisticated analytical instrumentation and a tedious sample preparation method is a challenge for environmental monitoring and mitigation. Here we present a novel yet simple analytical method for highly sensitive and specific detection of uranyl ions via photoluminescence quenching of CdS quantum dots. We have demonstrated a new approach for synthesizing highly water-soluble and strong photoluminescence-emitting CdS quantum dots (i.e., CdS-MAA and CdS-MAA-TU) of sizes less than 3 nm. The structural, morphological, and optical properties of both the batches of CdS quantum dots were thoroughly characterized by XRD, high-resolution transmission electron microscopy (HRTEM), zeta potential, UV-visible absorption, and photoluminescence spectroscopy. Compared to the batch of CdS quantum dots prepared by capping with only mercaptoacetic acid (CdS-MAA), the batch prepared by capping with mercaptoacetic acid and thiourea in tandem (CdS-MAA-TU) exhibited higher quantum yield= 16.64 ± 1.02%, and more importantly, CdS-MAA-TU exhibited significantly a higher order of photoluminescence quenching responses when treated with ultratrace concentrations of uranyl ions. Under the optimized conditions, the sensitivity of detecting uranyl ion by CdS-MAA-TU was several folds better (0.316 L/ μg) than that of CdS-MAA (0.0053 (L/μg/), as determined from their respective Stern-Volmer plots. Qualitatively, CdS-MAA-TU probe can be used for visual detection of uranyl ions of concentration greater than 5 μg/L. However, the instrumental method of analysis based on photoluminescence spectroscopy confirmed the feasibility for quantitative analysis of ultratrace concentrations of uranyl ions as implied from a very low limit of detection (LoD = 0.07 μg/L) and limit of quantification (LoQ = and 0.231 μg/L). Systematic studies revealed very high selectivity for uranyl ion detection, though minor interference from Cu(2+), Pb(2+), Hg(2+), CO3(2-), and SO4(2-) was found. The recovery analysis performed by spiking uranyl ions (0.5 μg/L to 10.0 μg/L) in groundwater and river water samples, confirmed the robustness of the as-developed CdS-MAA-TU QDs for detecting ultratrace levels of uranyl ions in real water sample matrix. The very simple and effective strategy reported here should facilitate developing reliable sensors for detecting uranyl ion contamination in drinking water.

A novel approach is presented to capture some of the potentially toxic elements (PTEs), other particulates and emissions during the heat treatment of e-waste using alumina adsorbents. Waste PCBs from mobile phones were mechanically crushed to sizes less than 1 mm; their thermal degradation was investigated using thermo-gravimetric analysis. Observed weight loss was attributed to the degradation of polymers and the vaporization of organic constituents and volatile metals. The sample assembly containing PCB powder and adsorbent was heat treated at 600 °C for times ranging between 10 and 30 min with air, nitrogen and argon as carrier gases. Weight gains up to ∼17% were recorded in the adsorbent thereby indicating the capture of significant amounts of particulates. The highest level of adsorption was observed in N2 atmosphere for small particle sizes of alumina. SEM/EDS results on the adsorbent indicated the presence of Cu, Pb, Si, Mg and C. These studies were supplemented with ICP-OES analysis to determine the extent of various species captured as a function of operating parameters. This innovative, low-cost approach has the potential for utilization in the informal sector and/or developing countries, and could play a significant role in reducing toxic emissions from e-waste processing towards environmentally safe limits.

A novel spherical magnetic nanocarrier of 100-150 nm dimensions made of pectin interacted with chitosan (MPCh-DS0.05) resulted in 99.5% encapsulation efficiency of diclofenac sodium (DS) as a model drug. Similarly, magnetic nanocarrier made of only pectin crosslinked with Ca(2+) (MPDS-0.05) resulted in only 60.6% encapsulation efficiency of DS. The increase in drug encapsulation efficiency (%) in MPCh-DS0.05 batch was due to synergistic drug encapsulation properties of pectin and chitosan. The structural and morphological features of these magnetic nanocarriers were studied by X-ray diffractometry (XRD), Fourier transform infrared-spectrometry (FT-IR), thermogravimetry, electron microscopy and dynamic light scattering (DLS) measurements. The magnetic properties were measured by vibrating sample magnetometer (VSM) and superconducting quantum unit interference device measurements (SQUID). The in vitro drug release was pH sensitive and exhibited sustained release sequentially in simulated gastric fluid (negligible release in 0-2h), simulated intestinal fluid (~69% release in 2-5h), simulated colonic fluid (5-60 h) and also in phosphate buffer at pH 7.4 (0-48 h). The drug release profile in phosphate buffer solution at pH 7.4 was in good agreement with swelling controlled mechanism on the basis of Korsemeyer-Peppas model.