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We present here a surface-enhanced Raman spectroscopy (SERS)-based platform for selectively detecting electrolyte cations. This platform facilitates the reorientation of the chromoionophore I (CHI) molecule positioned on the surface of silver nanoparticles, regulated by the targeted electrolyte cation within the ionophore-based ion-selective sensing framework. When exposed to the target ions, leading to deprotonation, the aromatic plane of the CHI molecule shifts from an endwise to an edgewise configuration on the SERS substrate surface. This reorientation improves the coupling of the induced dipole within the molecule and the induced electromagnetic field normal to the surface, leading to a heightened and more discernible SERS signal. Additionally, NMR data revealed a protonation-dependent conformational change in the CHI molecules. Upon protonation, the side chain of the CHI molecule extends away from its aromatic ring, whereas upon deprotonation, the carbon chain folds back and closely approaches the edge of the aromatic plane, further confirming this conclusion. Using Ca 2+ and Na + as examples, this method shows a detection limit of 0.1 μM for Ca 2+ and 1 μM for Na + with high selectivity. The successful application of the versatile and rapidly advancing SERS technique for electrolyte cation detection shows a promising pathway for enhancing current ion detection capabilities. As a preliminary demonstration, the total Ca 2+ concentration in undiluted human serum was successfully determined, with common matrix interference effectively circumvented.

Exposure to dust particles enriched with arsenic (As) is a significant health threat for populations living in Southeast Asian megacities. The mineralogical composition of dust particles is the key factor that controls the retention and release of As. This study investigated the degree of metal(oid)s pollution (As, Ca, Fe, K, Ga, Rb, Sr, Ti, V, Y, and Zr) in road dust of Dhaka city, Bangladesh. Enrichment factor and geoaccumulation index suggested that the road dust was heavily enriched with As, which triggers a comprehensive investigation of its controlling mechanisms and potential health risks by combining physicochemical and mineralogical information with multivariate analysis and a simulated probabilistic risk estimation model. Alkaline road dust (pH 1:5 ranges from 8.02 to 10.34) in Dhaka city was found to have significant enrichment of As. Dust alkalinity was possibly controlled by the presence of carbonate minerals, such as calcite. Quartz was identified as the dominant mineral phase followed by magnesium carbon arsenide (MgCAs 2 ). Carbonate mineral driven alkaline pH conditions in road dust would potentially trigger the release and mobilization of As to the environment. However, organic complexation can stabilize As on particle surfaces. Monte Carlo simulation-based health risk forecast suggested that the probability of As associated cancer risk has greatly exceeded the threshold value of 1E-4 for adults and children, and children are more vulnerable than adults. According to sensitivity analysis, the concentration of As and exposure duration (ED) posed the most significant impact (>58%) on risk estimation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Contaminants in road dusts can directly pose significant human health risks through oral ingestion, particle inhalation, and dermal contact. Therefore, this study has been designed to analyze heavy metal contaminations in 88 street dusts collected from the 22 high traffic sites and industrial areas of the Southeast Asian Megacity: Dhaka (capital of Bangladesh) using energy dispersive X-ray fluorescence (EDXRF) spectroscopy. This study revealed that the maximum Pb, Cd, Zn, Cr, Ni, As, Mn and Cu contents in the street dust samples were 18.9, 11.6, 239.2, 144.3, 37.1, 8.1, 261.5 and 49.6 mg/ kg respectively in which Ni and Pb concentration were 2 times, and Cd concentration was 200 times higher than the background level in soil; and As concentration was slightly higher than soil background level. The spatial distribution of heavy metal concentrations in street dust samples in Dhaka City was revealed that the hot spot areas of Pb, Ni, Cd and As were mainly associated with heavy traffic and industrial activities. The risk assessment strategies were used for this study for identifying the routes of exposure through oral ingestion, inhalation, and dermal contact by the fine particles (~75 μm) of street dust, especially for children based on the US EPA health risk models. Both non-carcinogenic and carcinogenic risks of heavy metals were characterized in street dust samples. Results based on the hazard index (HI), in the case of non-cancer effect, the ingestion of dust particles of children and adults in Dhaka City appeared to be the route of exposure to street dust that results in a higher risk for heavy metals, followed by dermal contact. This study revealed that the inhalation of re-suspended particles through mouth and nose were almost negligible. It was also noticed that children were experiencing the potential health risk due to HI for Cr (1.04), which was slightly higher than the safe level 1, and Cd (0.69) was close to the safe level 1. Reversely, cancer risk for Cr (i.e. 4.27 × 10 -6 ) was fallen within the range of threshold values (10 -4 to 10 -6 ) and As (i.e. 9.59 × 10 -7 ) was close to the upper limit of threshold values (10 -4 to 10 -6 )., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Fundamental understanding of interactions at the interface of biological molecules, such as proteins, and nanomaterials is crucial for developing various biocompatible hybrid materials and biosensing platforms. Biosensors comprising of graphene-based conductive nanomaterials offer the advantage of higher sensitivity and reliable diagnosis mainly due to their superior specific surface area and ballistic conductivity. Furthermore, conductive nanocomposite structures that immobilize proteins can synergize the properties of both transducers and molecular recognition elements improving the performance of the biosensing device. Here we report for the first time, using a combined molecular dynamics simulations and experimental approach, the interactions between avidin and graphene for the development of a sensing platform that can be used for the detection of biological macromolecules such as mismatch repair proteins through biotinylated DNA substrates. We find that the interactive forces between avidin and graphene are mainly hydrophobic, along with some van der Waals, electrostatic and hydrogen bonding interactions. Notably, the structure and function of the avidin molecule are largely preserved after its adsorption on the graphene surface. The MD results agree well with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) analysis of avidin immobilized on a graphenated polypyrrole (G-PPy) conductive nanocomposite confirming the adsorption of avidin on graphene nanoplatelets as observed from the Fourier-transform infrared spectroscopy (FTIR)., (Copyright © 2016 Elsevier B.V. All rights reserved.)