In this study, we present a simple colorimetric probe for detecting chromium species, i.e. Cr(vi) and Cr(iii), in aqueous solution using as-synthesized citrate-capped silver nanoparticles without further functionalization. Two types of silver nanoparticles, AgNP-I (10 ml sodium borohydride) and AgNP-II (30 ml sodium borohydride) were synthesized by varying the volume of the reducing agent. AgNP-I was proven to be specific for Cr(iii) only whereas AgNP-II would measure total chromium in a binary mixture of Cr(iii) and Cr(vi). The probe was tested in a binary mixture at a 1:1 ratio, containing the total chromium concentrations in the range of 500-5000 ppb. The sensing method was also successfully applied in a portable colorimeter with similar binary combinations paving the way for further on-site applications. © 2014 The Royal Society of Chemistry.

Amitava Mukherjee

Centre for Nanobiotechnology

Vellore Campus

Chandra Sekaran N

Elavarasi M

Rajeshwari A

Alex S.A

Nanda Kumar D

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Analytical Methods

A highly sensitive colorimetric sensor for Hg2+ was developed with unmodified AgNPs using an enzyme-based indirect method.

New Journal of Chemistry

Acetylcholinesterase inhibition-based colorimetric determination of Hg2+ using unmodified silver nanoparticles

In this study we present a colorimetric detection method for Cr (VI) in aqueous solution based on as synthesized silver nanoparticles (Ag NPs) without surface functionalization. The method principle involves reduction of Cr (VI) to Cr (III) by excess reductant present in as synthesized Ag NP dispersion, and subsequent aggregation of Ag NPs by Cr (III) leading to red-shift of the surface plasmon resonance (SPR) peak. The UV-vis absorption spectra, Zeta potentials, dynamic light scattering measurements, and scanning electron microscopy (SEM) confirmed the aggregation of the Ag NPs. Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.981) was obtained between the ratio of the absorbance at 550 nm to that at 390 nm (A 550/390) and the concentration of Cr (VI) over the range of 10 -3-10 -9 M [50 mg/L to 50 ng/L]. The reported probe has a limit of detection down to 1 nM, which, to the best of our knowledge, is the lowest ever reported for the colorimetric detection of Cr (VI). Furthermore, a remarkable feature of this method is that it involves a simple technique exhibiting high selectivity to Cr (VI) over other tested heavy metal ions. © 2012 Elsevier B.V. All rights reserved.

Sensors and Actuators B: Chemical

Selective colorimetric detection of nanomolar Cr (VI) in aqueous solutions using unmodified silver nanoparticles

In the current study we present a fluorescence probe for Cr(iii) in aqueous solution employing as-synthesized silver nanoparticles (Ag NPs) without surface labeling by any extrinsic fluorophore. The principle of the method involves aggregation of Ag NPs by Cr(iii) leading to a red-shift of the fluorescence emission peak from 420 to 684 nm for a corresponding excitation wavelength of 340 nm. The UV-visible absorption spectral studies, dynamic light scattering measurements, and scanning electron microscopy (SEM) corroborated the aggregation of the Ag NPs upon interaction with Cr(iii). Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.975) was observed between concentration of Cr(iii) and the fluorescence intensity at 684 nm in the range of 1 × 10 -3 to 2 × 10 -9 M (50 mg L -1 to 100 ng L -1). The reported probe has a limit of detection as low as 2 nM, which, to the best of our knowledge, is the lowest ever reported for the fluorescence detection of Cr(iii). The developed sensor was successfully tested with chromium containing real samples, such as groundwater and fresh water, demonstrating potential application in the field of environmental sensing. © The Royal Society of Chemistry. 2012.

Studies on fluorescence determination of nanomolar Cr(iii) in aqueous solutions using unmodified silver nanoparticles

Owing to widespread applications, synthesis and characterization of silver nanoparticles is recently attracting considerable attention. Increasing environmental concerns over chemical synthesis routes have resulted in attempts to develop biomimetic approaches. One of them is synthesis using plant parts, which eliminates the elaborate process of maintaining the microbial culture and often found to be kinetically favourable than other bioprocesses. The present study deals with investigating the effect of process variables like reductant concentrations, reaction pH, mixing ratio of the reactants and interaction time on the morphology and size of silver nanoparticles synthesized using aqueous extract of Azadirachta indica (Neem) leaves. The formation of crystalline silver nanoparticles was confirmed using X-ray diffraction analysis. By means of UV spectroscopy, Scanning and Transmission Electron Microscopy techniques, it was observed that the morphology and size of the nanoparticles were strongly dependent on the process parameters. Within 4 h interaction period, nanoparticles below 20-nm-size with nearly spherical shape were produced. On increasing interaction time (ageing) to 66 days, both aggregation and shape anisotropy (ellipsoidal, polyhedral and capsular) of the particles increased. In alkaline pH range, the stability of cluster distribution increased with a declined tendency for aggregation of the particles. It can be inferred from the study that fine tuning the bioprocess parameters will enhance possibilities of desired nano-product tailor made for particular applications. © 2009 Springer Science+Business Media B.V.

Journal of Nanoparticle Research

Process variables in biomimetic synthesis of silver nanoparticles by aqueous extract of Azadirachta indica (Neem) leaves

Sensitive and selective detection of trivalent chromium using hyper Rayleigh scattering with 5,5′-dithio-bis-(2-nitrobenzoic acid)-modified gold nanoparticles

Journal	Data powered by TypesetAnalytical Methods
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	1759-9660
Open Access	0