University of Johannesburg

About: University of Johannesburg is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Tourism. The organization has 8070 authors who have published 22749 publications receiving 329408 citations. The organization is also known as: UJ.

Towards green synthesis of monodisperse Cu nanoparticles: An efficient and high sensitive electrochemical nitrite sensor

Abstract: The development of highly stable and biocompatible Cu nanocomposite has been employed herein as an electrocatalytic active material for electrochemical sensing. The synthesis of carboxymethyl cellulose (CMC) stabilized Cu nanoparticles in aqueous medium under room temperature has been carried out. To identify the surface properties of the synthesized Cu nanoparticles, X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) studies have been carried out. The as-prepared Cu nanoparticles were dispersed with multi-walled carbon nanotubes (MWCNTs) and the resultant dispersion has been deposited over glassy carbon (GC) electrode to obtain Cu/MWCNTs/GC modified electrode. The Cu/MWCNTs modified GC electrode exhibits a well-defined oxidation peak at Epa = 0.93 V (vs. SCE) towards the oxidation of nitrite. Amperometric investigations of the modified electrode revealed a wide linear range for nitrite from 5 μM to 1260 μM with a sensitivity and detection limit of 455.84 μA mM−1 cm−2 and 1.8 μM, respectively. The proposed modified electrode displayed excellent selectivity and reproducibility and has been successfully utilized for determination of nitrite in real samples.

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

Abstract: 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. (C) 2012 Elsevier BM. All rights reserved.

Search for a light charged Higgs boson in the decay channel H+ -> c(s)over-bar in t(t)over-bar events using pp collisions at root s=7 TeV with the ATLAS detector

Abstract: A search for a charged Higgs boson (H+) in t (t) over bar decays is presented, where one of the top quarks decays via t -> H(+)b, followed by H+ -> two jets (c (s) over bar). The other top qu ...