Nadeem Baig

Impact of nanoparticles on human and environment: review of toxicity factors, exposures, control strategies, and future prospects

Nanotechnology has revolutionized the world through introduction of a unique class of materials and consumer products in many arenas. It has led to production of innovative materials and devices. Despite of their unique advantages and applications in domestic and industrial sectors, use of materials with dimensions in nanometers has raised the issue of safety for workers, consumers, and human environment. Because of their small size and other unique characteristics, nanoparticles have ability to harm human and wildlife by interacting through various mechanisms. We have reviewed the characteristics of nanoparticles which form the basis of their toxicity. This paper also reviews possible routes of exposure of nanoparticles to human body. Dermal contact, inhalation, and ingestion have been discussed in detail. As very limited data is available for long-term human exposures, there is a pressing need to develop the methods which can determine short and long-term effects of nanoparticles on human and environment. We also discuss in brief the strategies which can help to control human exposures to toxic nanoparticles. We have outlined the current status of toxicological studies dealing with nanoparticles, accomplishments, weaknesses, and future challenges.

Graphite pencil electrodes as electrochemical sensors for environmental analysis: a review of features, developments, and applications

Graphite pencil electrodes (GPEs) are carbon-based electrodes that are recognized by their low cost, simplicity, commercial availability, ease of modification and disposability. GPEs are attractive substrates for electrochemical sensing because of their unique feature of “disposability” compared to other commonly used carbon-based electrodes. Mechanically rigid GPEs are easy to modify and miniaturize. The sensitivity and selectivity of GPE toward certain analytes can be enhanced by applying different modification materials. The primary focus of this review article is to highlight the applications of GPEs in the analysis of inorganic and organic pollutants in different environmental matrices. This review gives a brief overview of the various types of inorganic and organic pollutants and their impact on the environment. The key features of modified GPEs that enhance their electrocatalytic activity toward detection of certain target analytes are critically appraised. In the end, we summarize the current status, weaknesses and future prospects of GPE based sensors for environmental analysis.

A novel, fast and cost effective graphene-modified graphite pencil electrode for trace quantification of L-tyrosine

A simple and novel method for detecting L-tyrosine in urine was introduced using a graphene-modified graphite pencil electrode (GR-modified GPE). Graphene oxide (GO) was directly reduced using cyclic voltammetry (CV) on the surface of the GPE. The synthesized GO was characterized by FTIR and Raman spectroscopy. The morphology of the electrode surface was characterized by field emission-scanning electron microscopy (FE-SEM) and the electrochemical properties were characterized by CV, electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV). The graphene layer on the GPE dramatically enhanced the electroactive surface area and electrochemical oxidation of L-tyrosine. A satisfactory linear response was obtained in the square wave voltammogram from 0.8 μM to 60 μM, with a regression constant (R2) of 0.9995. The modified electrode yielded a low L-tyrosine limit of detection of 0.07 μM. The present modification process is completed within 5 min compared to other reported time-consuming methods. The modified electrode surface was free from interfering species and successfully applied to the determination of L-tyrosine in human urine. The low cost and easy to modify electrode displayed excellent sensitivity, selectivity, and reproducibility, a low limit of detection and a wide linear response range.

A cost-effective disposable graphene-modified electrode decorated with alternating layers of Au NPs for the simultaneous detection of dopamine and uric acid in human urine

A disposable electrode based on a highly sensitive and readily fabricated arrangement of alternating AuNP and graphene layers was introduced for the simultaneous determination of dopamine and uric acid. The process by which the disposable electrodes were fabricated is simple, fast, and accomplished through the direct electrochemical reduction of graphene oxide and Au(III) onto a graphite pencil electrode surface. Extraordinary electrocatalytic activities of the graphene nanocomposite were observed in the presence of dopamine and uric acid. The synthesized graphene oxide was characterized by Raman and FTIR spectroscopy. The surface morphology, elemental, and electrochemical characterization of the bare and modified electrodes were analyzed by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Good linear sensitivity was obtained over the ranges of 0.1–25 μM for dopamine and 0.09–25 μM for uric acid under optimal conditions using square wave voltammetry. Very low limits of detection of 0.024 μM (dopamine) and 0.029 μM (uric acid) were attained from the fabricated electrochemical sensors. The dopamine and uric acid peak separation was 151 mV. The graphene nanocomposite on the GPE surface effectively improved the peak separation, electroactive surface area, sensitivity, selectivity, and reproducibility. The fabricated electrode behaved well in the presence of high concentrations of ascorbic acid and in the presence of other potentially interfering compounds. The electrochemical sensors did not undergo surface fouling, particularly in the presence of dopamine, which tends to severely foul surfaces after a single measurement. The cost effectiveness of the sensor, the short fabrication time, and the lack of surface fouling, especially in the presence of dopamine, render these novel electrodes both multi-use and disposable.

Bis(selenobenzoato)dibutyltin(IV) as a single source precursor for the synthesis of SnSe nanosheets and their photo-electrochemical study for water splitting

A new organo-tin complex has been synthesized and used as a single source precursor for the synthesis of SnSe nanosheets by the hot injection method and thin films by the aerosol assisted chemical vapor deposition (AACVD) method. The films were deposited on glass substrates at three different temperatures. The textural quality and preferential growth were found to be significantly altered by changes in the deposition temperature. Oleylamine capped nanosheets and the as-deposited thin films by AACVD were characterized by powder X-ray diffraction (p-XRD) and microscopic techniques. The thin films were also studied by Raman spectroscopy. The stoichiometry is marginally affected by temperature, and all films were slightly selenium deficient. The synthesized material was also evaluated for the photoelectrochemical (PEC) splitting of water. The PEC study revealed the bifunctional nature of the material, which can be applied for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), by switching the applied potential.

Synthesis, structural characterization, electrochemical behavior and anticancer activity of gold(III) complexes of meso-1,2-di(1-naphthyl)-1,2-diaminoethane and tetraphenylporphyrin

Three gold(III) complexes, [Au(npen)Cl2]Cl·2H2O (1), [Au(npen)2]Cl3 (2) and [Au(TPP)]Cl (3) (npen = meso-1,2-di(1-naphthyl)-1,2-diaminoethane, TPP = meso-tetraphenylporphyrin) have been synthesized and characterized using elemental analysis, IR and NMR spectroscopy, and one of them (1) by X-ray crystallography. The structure of 1 consists of a [Au(npen)Cl2] complex ion, a chloride counter ion and two water molecules. The gold atom in the complex ion adopts a distorted square planar geometry. The interactions of 1 and 2 with L-tyrosine, glutathione and lysozyme were studied electrochemically. The electrochemical measurements indicated that gold(III) remained stable and did not undergo reduction upon interaction with proteins. The in vitro cytotoxic properties of the complexes as well as of cisplatin were evaluated on three human cancer cell lines, A549 (lung cancer cells), MCF7 (breast cancer cells) and HCT15 (colon cancer cells) using MTT assay. The results indicated that the prepared gold(III) complexes were more potent than cisplatin in inhibiting the growth of the selected cancer cells. The IC50 data revealed that complex 3 was the most effective antiproliferative agent.

A new water stable zinc metal organic framework as an electrode material for hydrazine sensing

Metal–organic frameworks (MOFs) are an emerging class of materials exhibiting high surface areas, controlled pore sizes, open metal sites and organic linkers. Utilizing MOFs as direct electrode materials for electrochemical sensing can offer inherent advantages such as containing a sensing element and a redox mediator in a single molecule; however, the direct use of MOFs as electrode materials is hindered because of their insulating nature and less stability in an aqueous medium. In this study, a new water stable Zn-MOF was synthesized and used directly as an electrode material. The Zn-MOF possesses good ability to electrocatalyze the hydrazine oxidation reaction. The Zn-MOFs inherent poor conductivity was overcome by including a hydrophobic electrolyte, tetrakis(4-chlorophenyl)borate tetradodecylammonium salt (ETH 500), during the fabrication of the Zn-MOF membrane. After coating a thin film of the nafion-ETH500 supported Zn-MOF over a glassy carbon electrode (GCE), the response for hydrazine oxidation was substantially improved. Linear sweep voltammetry (LSV) demonstrated a wide linear range from 20 to 350 μM (R2 = 0.9922) for hydrazine. A detection limit of 2 μM (n = 3) was observed. The electrochemical behavior of the ZnMOF/ETH500/nafion modified GCE revealed that MOFs have a promising future as electrode materials for direct electrochemical sensing.

Natural‐Light‐Initiated 3D Macro Zigzag Architecture of Graphene‐Reinforced Polystyrene for Gravity‐Driven Oil and Water Separation

Abstract Superhydrophobic 3D robust materials are introduced for the separation of hexane and water. For the first time, novel 3D zigzag polystyrene on graphene‐incorporated polyurethane (3D zz‐PS/GR/PU) is prepared using exclusively natural sunlight without any chemical initiator. The zigzag polystyrene growth is accomplished by polymerizing the styrene vapors. The natural sunlight provides a compact 3D zz‐PS/GR/PU material with superoleophilic and hydrophobic channels that allow for the rapid passage of oil, whereas water is entirely prevented from passing. The 3D zz‐PS/GR/PU compact channels are transformed into the compressible material by treating them with toluene without affecting the hydrophobicity of the material. The 3D zz‐PS/GR/PU displays a high‐water contact angle of approximately 150°. The developed materials are characterized by FTIR, SEM, and BET. The graphene incorporation makes surface area of the 3D zz‐PS/GR/PU substantially large compared with PU. It is improved from 15 to 67 m2 g−1. The pore size of the adsorption and desorption in the 3D zz‐PS/GR/PU is also reduced from 354 and 352 Å to 34 and 33 Å. The 3D zz‐PS/GR/PU satisfies the requirement of high‐demanding superhydrophobic materials, like a low‐cost fabrication process, reusability, and tunability. This strategy can trigger large‐scale production with a controlled morphology.