Fluorometric detection of bisphenol A using ß-cyclodextrin-functionalized ZnO QDs.

The estrogenic property of bisphenol A (BPA) leads to potential adverse health and ecological effects. A simple, selective, and cost-effective sensor capable of detecting BPA would have a noteworthy relevance for the environmental system. The present work illustrates the synthesis and characterization of ß-cyclodextrin (ß-CD) functionalized zinc oxide (ZnO) quantum dots (QDs) for the selective detection of BPA. BPA has a fluorescence quenching effect on functionalized ZnO QDs, and the decrease in fluorescence intensity is associated with the BPA concentration between 2 and 10 µM. Under the optimum reaction condition, a good linear correlation was obtained between relative fluorescence-quenching intensity of ß-cyclodextrin-functionalized ZnO QDs and BPA concentration (R2 = 0.9891). The lower detection limit of functionalized QDs for BPA was estimated to be 0.19 µM, which is lower than the toxic limits in aquatic biota. The fluorescence-based detection of BPA may be ascribed to the electron transfer mechanism, which is elucidated with scientific details from the literature.

Photocatalytic degradation of p-nitrophenol using biologically synthesized ZnO nanoparticles.

The present work deals with the photocatalytic degradation of p-nitrophenol as it is a United States Environmental Protection Agency-listed priority pollutant and has adverse environmental and health effects. To eradicate the detrimental environmental impact of p-nitrophenol, the biologically synthesized ZnO nanoparticles were used as a photocatalyst. The degradation of p-nitrophenol was confirmed by decreasing the absorbance value at a characteristic wavelength of 317 nm using the UV-vis spectrophotometer. Reaction parameters such as ZnO photocatalyst concentration of 0.1 g/L at pH 11 in the presence of H2O2 (5 mM) were found to be optimum conditions for p-nitrophenol degradation. The photocatalytic degradation was slowly enhanced in the presence of H2O2 as an electron acceptor. The kinetics of nitrophenol degradation was studied, which follows the pseudo-first-order reaction. The photocatalytic degradation of p-nitrophenol was characterized by using total organic carbon, chemical oxygen demand, and high-performance liquid chromatography analyses. This method is found to be effective as it is environmentally friendly, free of toxic chemicals.

Removal of methylene blue dye using nano zerovalent iron, nanoclay and iron impregnated nanoclay - a comparative study.

There has been an increasing challenge from the emission of methylene blue (MB) dye-containing wastewater and its management methods in industry. The sorption process is one conventionally used method. In this study, nanoclay, nano zero valent iron (nZVI), and iron impregnated nanoclay were prepared and studied for the removal of MB dye in batch mode. The effects of operating parameters like pH, dye concentration, sorbent dosage, and contact time were investigated and optimized. The nZVI, nanoclay, and iron impregnated nanoclay sorbents showed zeta potentials of -32.1, -53.4, and -40.7 mV, respectively. All the nano adsorbents were crystalline. The nanoclay was characterized by an average surface area, pore volume and pore diameter of 43.49 m2 g-1, 0.104 cm3 g-1 and 2.806 nm, respectively. nZVI showed a surface area of 47.125 m2 g-1, pore volume of 0.119 cm3 g-1, and pore diameter of 3.291 nm. And iron impregnated nanoclay showed a surface area of 73.110 m2 g-1 with a pore volume of 15 cm3 g-1 and a pore diameter size of 3.83 nm. A Langmuir EXT nitrogen gas adsorption isotherm (R 2 ∼ 0.99) was the best fit. The thermodynamics parameters, such as ΔG° (-12.64 to -0.63 kJ mol-1), ΔH° (+0.1 to +62.15 kJ mol-1) and ΔS° (+0.10 to +0.22 kJ mol-1), confirmed that a spontaneous and endothermic adsorption process took place at a high rate of disorder. Iron impregnated nanoclay showed higher negative Gibbs free energy (-12.64 kJ mol-1), higher enthalpy change (+62.5 kJ mol-1) and entropy (+0.22 kJ mol-1) and gave a better MB removal performance. In addition, the lower negative heat of enthalpy for all adsorptions proved the dominance of physisorption. The methylene blue adsorption isotherm on nZVI and nanoclay showed the best fit with the Freundlich isotherm model with correlation coefficients (R 2) ∼0.98 and 0.99, respectively. Whereas the Langmuir adsorption isotherm was the best fit for iron impregnated nanoclay (R 2 ∼ 0.98). The adsorption activities of nZVI, nanoclay and iron impregnated nanoclay were fitted to a pseudo-second-order kinetic model with correlation coefficients (R 2) of 0.999, 0.997 and 0.983, respectively. The optimal pH 7.0 (RE: 99.1 ± 0.73%), initial MB concentration 40 ppm (RE: 99.9 ± 0.03%), contact time 120 min (RE: 99.9 ± 0.9%), and adsorbent dose 80 (99.9 ± 0.03%) were obtained for iron impregnated nanoclay. The optimal operational parameters of nanoclay and nZVI, respectively, were pH 11.0 and 13.0, initial MB concentration 20 and 20 ppm, adsorbent dose 100 and 140 mg, and contact time 120 and 140 min. In general, iron impregnated nanoclay has shown promising cationic dye adsorbance for industrial applications; but a recyclability test is suggested before scale-up.

Adsorptive removal of trivalent and pentavalent arsenic from aqueous solutions using iron and copper impregnated melanin extracted from the marine bacterium Pseudomonas stutzeri.

The metalloid arsenic is one of the most conspicuous groundwater contaminants in the Indian subcontinent and its removal from aqueous medium is the main focus of this study. The study aims at functionalising melanin using iron and copper for the efficient removal of arsenic and rendering water fit for consumption. Melanin obtained from the marine bacteria Pseudomonas stutzeri was functionalised by iron impregnation (Fe-melanin) and copper impregnation (Cu-melanin). Morphological studies using FESEM portrayed the impregnated iron and copper granules on the surface of melanin, while XRD analysis confirmed the presence of Fe2O3 and CuO on melanin. Adsorption studies on As (V) and As (III) were conducted using Fe-melanin and Cu-melanin for different operating variables like pH, temperature and contact time. More than 99% per cent of As (III) and As (V) from water was removed at a pH range between 4 and 6 within 50 min in the case of Fe-melanin and 80 min for Cu-melanin. Adsorption equilibrium studies showed better fit with Langmuir adsorption isotherm and had good agreement with Redlich-Peterson's three-parameter model. The maximum adsorption capacities of Fe-melanin and Cu-melanin obtained from Langmuir adsorption model are 50.12 and 20.39 mg/g, respectively, for As (V) and similarly 39.98 and 19.52 mg/g, respectively, for As (III). Arsenic-binding to the functionalised melanin was confirmed using FT-IR and the XPS analysis. Reuse of the adsorbent was effectively done by desorbing the iron and copper together with the bound As (III) and As (V) and further re-impregnation of iron and copper in melanin. Re-functionalised melanin showed 99% adsorption efficiency up to four cycles of adsorption/desorption.

Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes.

Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon-Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up.

Solar assisted photocatalytic degradation of organic pollutants in the presence of biogenic fluorescent ZnS nanocolloids.

The main aim of this study was to ascertain the photocatalytic degradation of organic pollutants present in aqueous phase using fluorescent biogenic ZnS nanocolloids produced from an endophytic fungus Aspergillus flavus. The degradation studies were carried out using different organic pollutants such as methyl violet (MV), 2,4-dichlorophenoxyacetic acid (2,4-D) and paracetamol (PARA) for 120 min, 270 min and 240 min, respectively, at pH varying from 3.0 to 11.0. The results from this study indicate that the degradation efficiency of ZnS nanocolloids for MV, 2,4-D and PARA were 87%, 33% and 51%, respectively, at the optimum concentration of 100 mg/L of the tested organic pollutants. At different time intervals, the samples were analyzed for their chemical oxygen demand (COD) and total organic carbon (TOC) contents. The reduction of COD and TOC were 78% and 74% for MV at 120 min; 55.5% and 57.2% for 2,4-D at 270 min and 47.6% and 44.5% for PARA at 240 min, respectively. The degradation pathway was determined based on the mass spectrum and the intermediates formed; in addition, the interaction between organic pollutants and nanocolloids was also elucidated based on atomic force microscopy (AFM) and fluorescence spectrum.

Bioinspired ZnS:Gd Nanoparticles Synthesized from an Endophytic Fungi Aspergillus flavus for Fluorescence-Based Metal Detection.

Recently, several nonconventional sources have emerged as strong hotspots for the biosynthesis of chalcogenide quantum dots. However, studies that have ascertained the biomimetic methodologies that initiate biosynthesis are rather limited. The present investigation portrays a few perspectives of rare-earth(Gd)-doped ZnS biosynthesis using the endophytic fungi Aspergillus flavus for sensing metals based on their fluorescence. Analysis of ZnS:Gd nanoparticles was performed by elemental analysis, energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), and transmission electron microscopy (TEM). The results of TEM demonstrated that the particles were polycrystalline in nature, with a mean size of 10-18 nm. The fluorescence amenability of the biogenic ZnS nanoparticles was further used for the development of a simple and efficient sensing array. The results showed sensitive and detectable quenching/enhancement in the fluorescence of biogenic colloidal ZnS nanoparticles, in the presence of Pb (II), Cd (II), Hg (II), Cu (II) and Ni (II), respectively. The fluorescence intensity of the biogenic ZnS:Gd nanoparticles was found to increase compared to that of the ZnS nanoparticles that capacitate these systems as a reliable fluorescence sensing platform with selective environmental applications.

Adsorption of ibuprofen using cysteine-modified silane-coated magnetic nanomaterial.

Industrialization and growth of the pharmaceutical companies have been a boon to the mankind in our day to day life in myriad ways. However, due to the uninhibited release of these active pharmaceutical compounds into the water systems has caused detrimental effects to the genetic pool. In this study, L-cysteine-modified 3-glycidyloxypropyltrimethoxysilane-coated magnetic nanomaterial showed a maximum removal of the efficiency of 82.90% for the nanomaterial dosage of 30 mg at an initial concentration of 50 mg L-1 at pH 6.0. Further, the nanomaterial showed reusability efficiency up to 80% for three cycles. The adsorption kinetics follow the pseudo-second-order reaction and the adsorption isotherm model best fits the Langmuir isotherm proving the adsorption process to be a monolayer sorption on a monolayer surface. This magnetic nanomaterial could serve as a promising tool for the removal of pharmaceutical compounds from aqueous solutions. Graphical abstract ᅟ.

Impact of precursor concentration on biological synthesis of cobalt oxide nanoparticles.

The data provided in the article is in association with the journal article "Synthesis of cobalt oxide nanoparticles using endophytic fungus Aspergillus nidulans". Characterization data (ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS) analysis, scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM)) of nanoparticles synthesized using different precursor concentrations (2 mM and 10 mM) have been presented in this article. Data obtained by t-test and F-test have been given for absorbance values exhibited by nanoparticles synthesized using different concentrations. Required figures and table have been depicted.

Data on the removal of heavy metals from aqueous solution by adsorption using melanin nanopigment obtained from marine source: Pseudomonas stutzeri.

Heavy metals are one of deadly contaminants in ground water across the globe. Thus, herein, this data set comprises experimental and modelled data on the removal of heavy metals from ground water using melanin synthesized by the marine bacteria Pseudomonas stutzeri. Characterization of biosynthesized melanin and modelling of the kinetic and the thermodynamic study on adsorption of heavy metals such as mercury (Hg(II)), lead (Pb(II)), chromium (Cr(VI)), and copper (Cu(II)) are included in this article. Apart from the study of parameters involved in adsorption such as pH, temperature, concentration and time; the data from these studies are modelled to analyze the nature and characteristic of heavy metals adsorbing to melanin nanoparticles. The figures from models, results from models as tables, characterization and analytical figures are depicted in this work.

Biosynthesis of cobalt oxide nanoparticles using endophytic fungus Aspergillus nidulans.

Metallic oxide nanoparticles have profound applications in electrochemical devices, supercapacitors, biosensors and batteries. Though four fungi were isolated from Nothapodytes foetida, Aspergillus nidulans was found to be suitable for synthesis of cobalt oxide nanoparticles, as it has proficient tolerance towards metal under study. The broth containing precursor solution and organism Aspergillus nidulans had changed from pink to orange indicating the formation of nanoparticles. Characterization by x-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray analysis (EDX) confirmed the formation of spinel cobalt oxide nanoparticles at an average size of 20.29 nm in spherical shape with sulfur-bearing proteins acting as a capping agent for the synthesized nanoparticles. The nanoparticles could be applied in energy storage, as a specific capacitance of 389 F/g showed competence. The study was a greener attempt to synthesize cobalt oxide nanoparticles using endophytic fungus.

Source apportionment studies on particulate matter (PM10 and PM2.5) in ambient air of urban Mangalore, India.

Particulate matter (PM10 and PM2.5) samples were collected from six sites in urban Mangalore and the mass concentrations for PM10 and PM2.5 were measured using gravimetric technique. The measurements were found to exceed the national ambient air quality standards (NAAQS) limits, with the highest concentration of 231.5 µg/m3 for PM10 particles at Town hall and 120.3 µg/m3 for PM2.5 particles at KMC Attavar. The elemental analysis using inductively coupled plasma optical emission spectrophotometer (ICPOES) revealed twelve different elements (As, Ba, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Sr and Zn) for PM10 particles and nine different elements (Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr and Zn) for PM2.5 particles. Similarly, ionic composition of these samples measured by ion chromatography (IC) divulged nine different ions (F-, Cl-, NO3-, PO43-, SO42-, Na+, K+, Mg2+ and Ca2+) for PM10 particles and ten different ions (F-, Cl-, NO3-, PO43-, SO42-, Na+, NH4+, K+, Mg2+ and Ca2+) for PM2.5 particles. The source apportionment study of PM10 and PM2.5 for urban Mangalore in accordance with these six sample sites using chemical mass balance model (CMBv8.2) revealed nine and twelve predominant contributors for both PM10 and PM2.5, respectively. The highest contributor of PM10 was found to be paved road dust followed by diesel and gasoline vehicle emissions. Correspondingly, PM2.5 was found to be contributed mainly from two-wheeler vehicle emissions followed by four-wheeler and heavy vehicle emissions (diesel vehicles). The current study depicts that the PM10 and PM2.5 in ambient air of Mangalore region has 70% of its contribution from vehicular emissions (both exhaust and non-exhaust).

Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri.

The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution.

Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection.

Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II-IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2+ and Mn2+ in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV-Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem.

Exploring the fungal protein cadre in the biosynthesis of PbSe quantum dots.

While a large number of microbial sources have recently emerged as potent sources for biosynthesis of chalcogenide quantum dots (QDs), studies regarding their biomimetic strategies that initiate QD biosynthesis are scarce. The present study describes several mechanistic aspects of PbSe QD biosynthesis using marine Aspergillus terreus. Scanning electron microscopic (SEM) studies indicated distinctive morphological features such as abrasion and agglomeration on the fungal biomass after the biosynthesis reaction. Further, the biomass subsequent to the heavy metal/metalloid precursor was characterized with spectral signatures typical to primary and secondary stress factors such as thiol compounds and oxalic acid using Fourier Transform Infra-Red Spectroscopic (FTIR) analysis. An increase in the total protein content in the reaction mixture after biosynthesis was another noteworthy observation. Further, metal-phytochelatins were identified as the prominent metal-ion trafficking components in the reaction mixture using Liquid Chromatography Mass Spectroscopic analysis (LCMS). Subsequent assays confirmed the involvement of metal binding peptides namely metallothioneins and other anti-oxidant enzymes that might have played a prominent role in the microbial metal detoxification system for the biosynthesis of PbSe QDs. Based on these findings a possible mechanism for the biosynthesis of PbSe QDs by marine A. terreus has been elucidated.

Microbial synthesis of chalcogenide semiconductor nanoparticles: a review.

Chalcogenide semiconductor quantum dots are emerging as promising nanomaterials due to their size tunable optoelectronic properties. The commercial synthesis and their subsequent integration for practical uses have, however, been contorted largely due to the toxicity and cost issues associated with the present chemical synthesis protocols. Accordingly, there is an immediate need to develop alternative environment-friendly synthesis procedures. Microbial factories hold immense potential to achieve this objective. Over the past few years, bacteria, fungi and yeasts have been experimented with as eco-friendly and cost-effective tools for the biosynthesis of semiconductor quantum dots. This review provides a detailed overview about the production of chalcogen-based semiconductor quantum particles using the inherent microbial machinery.

Optimization and kinetic modeling of cell-associated camptothecin production from an endophytic Fusarium oxysporum NFX06.

The production of cell-associated camptothecin (CPT) from an endophytic fungus Fusarium oxysporum NFX06 isolated from Nothapodytes foetida and its kinetics studies were proposed. Response surface methodology (RSM) based on central composite design (CCD) was used to construct a model to describe the effects of substrate concentration. Three independent variables (dextrose, peptone, and MgSO4) were successfully employed to study the yield of CPT under submerged fermentation. The maximum yield of CPT obtained from CCD was about 598.0 ng/g biomass. The model-validated optimum predicted CPT yield and experimental CPT yield from the biomass were found to be 628.08 ng/g and 610.09 ng/g at the concentrations of dextrose 42.64 (g/L), peptone 9.23 (g/L), and MgSO4 0.26 (g/L) respectively. The predicted yield of CPT was 4.90% higher than the value obtained from CCD and 2.85% higher than the value obtained from experiment conducted at optimum conditions. The kinetic parameters, maximum specific growth rate µmax=1.212 day(-1), growth-associated CPT production coefficient (α=29.35 ng/g biomass), and non-growth-associated CPT production coefficient (ß=0.03 ng CPT/g biomass-day) were obtained. The logistic model was found suitable to predict mycelial growth with a high determination coefficient (R2). Luedeking-Piret and modified Luedeking-Piret models were employed to represent the product kinetics and substrate consumption kinetics. A good concurrence was found between the experimental and predicted values, representing that the unstructured models were able to illustrate the fermentation profile effectively.

The uptake mechanism of Cd(II), Cr(VI), Cu(II), Pb(II), and Zn(II) by mycelia and fruiting bodies of Galerina vittiformis.

Optimum concentrations of heavy metals like copper, cadmium, lead, chromium, and zinc in soil are essential in carrying out various cellular activities in minimum concentrations and hence help in sustaining all life forms, although higher concentration of these metals is lethal to most of the life forms. Galerina vittiformis, a macrofungus, was found to accumulate these heavy metals into its fleshy fruiting body in the order Pb(II) > Cd(II) > Cu(II) > Zn(II) > Cr(VI) from 50 mg/kg soil. It possesses various ranges of potential cellular mechanisms that may be involved in detoxification of heavy metals and thus increases its tolerance to heavy metal stress, mainly by producing organic acids and phytochelatins (PCs). These components help in repairing stress damaged proteins and compartmentalisation of metals to vacuoles. The stress tolerance mechanism can be deduced by various analytical tools like SEM-EDX, FTIR, and LC-MS. Production of two kinds of phytochelatins was observed in the organism in response to metal stress.