Rapid and high precision detection of toxic metal ions is one of the chief requirements today to combat environment pollution. Gold nanoparticles play a key role in this by assisting the development of smart sensors and detection agents. Their high surface to volume ratio and unique optical property facilitates the development of high sensitive analytical GNP based bio-sensing tools. Recently, a major research thrust area has been the design and development of smartly fabricated GNPs as probes for selective detection of toxic contaminates and metal pollutants. In this review we focus on the use of GNPs and its functionalization for colorimetric detection of metal ions. Colorimetric detection enables cost effective and simple monitoring of toxic ions accompanied with the advantages of on-site applicability, avoids complex instrumentation, ease of analysis and usage. We also discuss the promising prospects and future potentiality of GNPs to serve as next generation multi-functional sensing tools and “lab-on-chip” detection agents.

Gold nanoparticles as efficient sensors in colorimetric detection of toxic metal ions: A review

The stress response is protective: cross protection in fish

Lead toxicity is a major public health issue in developed and developing countries. Both acute and chronic lead exposure has the potential to cause many deleterious systematic effects including hypertension, frank anemia, cognitive deficits, infertility, immune imbalances, delayed skeletal and deciduous dental development, vitamin D deficiency, and gastrointestinal effects. The underlying mechanisms for all these systemic effects have not been elucidated completely. However, the most plausible cause is free radical damage. In addition to this, lead being a divalent cation can surrogate for calcium at multiple levels affecting various cell signaling pathways. The molecular basis of lead exposure resulting in various systemic effects is being extensively explored. The reports include single nucleotide polymorphisms, epigenetic modifications in susceptible individuals, and the most recent reports also feature regulatory RNA molecules - miRNAs. However, many genetic targets are identified, but their possible mechanisms are still an area to be explored. Additional studies are needed in different population groups to validate the existing findings, as well as to find newer targets that may help in better understanding the molecular mechanisms contributing to lead toxicity. Furthermore, newer strategies for lead risk assessment becomes necessary as the previously recognized "safe" level of lead is also being found to be associated with negative health outcomes.

Clinical and molecular aspects of lead toxicity: An update

Antioxidant defense system, immune response and erythron profile modulation in gold fish, Carassius auratus, after acute manganese treatment

Manganese dioxide (MnO2 ) is a promising photo-thermo-electric-responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO2 single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO2 -based composites via the construction of homojunctions and MnO2 /semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO2 -based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high-efficiency MnO2 -based materials for comprehensive environmental applications is provided.

MnO2 -Based Materials for Environmental Applications.

In this study, the biosorption mechanisms of methylene blue (MB) and Cr(III) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with ab initio simulations. Factors that affect the adsorption such as pH, adsorption time, adsorbent dosage and initial adsorbate concentration, are fully considered. Five isotherm models—Langmuir, Freundlich, Sips, Temkin, and Dubinin–Radushkevich—are employed to estimate the capacity of pomelo peel adsorption, whereas four kinetic models—pseudo-first-order, pseudo-second-order, Elovich and intra-diffusion models—are also used to investigate the mechanisms of the uptake of MB and Cr(III) onto the pomelo fruit peel. The maximum biosorption capacities calculated from the Langmuir models for MB and Cr(III) at 303 K are, 218.5 mg g−1 and 11.3 mg g−1, respectively. In particular, by combining, for the first time, the experimental FT-IR spectra with those obtained from ab initio calculations, we are able to demonstrate that the primary adsorption mechanisms of the uptake of MB onto pomelo fruit peel are electrostatic attraction and hydrogen-bond formations, whereas the adsorption mechanisms for Cr(III) are electrostatic attraction and n–d interactions.

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Insight into the adsorption mechanisms of methylene blue and chromium(iii) from aqueous solution onto pomelo fruit peel

Chitosan-MnO2 nanocomposite for effective removal of Cr (VI) from aqueous solution

Diazo-coupled calix[4]arenes for qualitative analytical screening of metal ions.

Transition metal ion selective ortho-ester diazophenylcalix[4]arene.

Experimental results proved that the development of Colletotrichum capsici B4 is extremely sensitive to water-soluble chitosan (WSC) and inhibitory effects increase with increasing concentrations of WSC In the in vitro test, the results showed that the entire prevention of conidial germination and mycelial diameter development are recognized in a potato dextrose agar medium containing 04% and 08% WSC, respectively WSC was more efficient in a potato dextrose broth where it absolutely prevented the mycelial development of C capsici B4 at a concentration of 032% WSC treatments considerably decreased disease prevalence and the lesion diameter of anthracnose disease on chilli pepper fruits in the in vivo experiments Experiments in biochemistry indicated that the activities of the key defense-related enzymes in peel, consisting of chitinase, β-1,3-glucanase and total phenolic content, were increased by both C capsici B4 infection and C capsici B4 treatment, and was further treated with a 05% WSC concentration

Practical applications
From the present studies we conclude that water-soluble chitosan (WSC) can directly inhibit the development of C capsici B4 isolated from infected chili pepper fruits showing typical symptoms of anthracnose in in vitro and effectively control anthracnose in chili pepper fruit in in vivo with concentration-dependent antifungal effects These findings suggest that WSC may be recognized as a feasible effective alternative to artificial fungicides for postharvest disease control of chili pepper fruits

Le Van Tan

Papers

Insight into the adsorption mechanisms of methylene blue and chromium(iii) from aqueous solution onto pomelo fruit peel

Chitosan-MnO2 nanocomposite for effective removal of Cr (VI) from aqueous solution

Diazo-coupled calix[4]arenes for qualitative analytical screening of metal ions.

Transition metal ion selective ortho-ester diazophenylcalix[4]arene.

Antifungal activity of water‐soluble chitosan against Colletotrichum capsici in postharvest chili pepper