Novel SeS2-loaded Co MOF with Au@PANI comprised electroanalytical molecularly imprinted polymer-based disposable sensor for patulin mycotoxin.

An SeS2-loaded Co MOF and Au@PANI nanocomposite comprising the base matrix of the electrode was developed with electropolymerized molecularly imprinted polymer (MIP) consisting of p-aminobenzoic acid (PABA) and patulin (PT) to detect PT molecules based on the PT imprinted cavities. SeS2@Co MOF and Au@PANI were synthesized using hydrothermal synthesis and interfacial polymerization strategies, respectively. A suitable functional monomer to fabricate the MIP platform was selected using the density functional theory (DFT/M06-2X method). Higher electrochemical active surface area (0.985 cm2 which is 6.99 times higher than the bare SPE) and a lower charge transfer resistance (Rct = 27.8 Ω) at the MIP/Au@PANI/SeS2@Co MOF electrode was achieved based on the higher number of adsorptive sites and enhanced conductivity (electron transfer rate constant (ks = 3.24 × 10-3 s-1) of the sensing platform. The fabricated MIP sensor performance was studied in 10 mM PBS (pH = 6.4), where an improved detection limit (0.66 pM) for PT and a broad logarithmic linear dynamic range (0.001-100 nM) were both observed. The sensor possessed higher selectivity (Imprinting factor = 15.4 for PT), excellent reusability (%RSD of 10 cycles = 2.49%), high storage stability (6.7% lost after 35 days), and robust reproducibility (%RSD = 3.22%) The as-prepared MIP-based PT sensor was applied to detect PT in a real-time apple juice sample (10% diluted with PBS) with a recovery % ranging from 94.5 to 106.4%. The proposed sensor possesses great advantages in terms of cost-effectiveness, providing a simple detection strategy for long-term storage stability, and reversible cycle measurements.

Twisted Eigen Can Induce Proton Transfer at a Hydrophobic-Hydrophilic Interface.

The investigation of proton localization at a hydrophobic-hydrophilic interface is an important problem in chemical and materials sciences. In this study, protonated benzene (i.e., benzenium ion) and water clusters [BZH+Wn (where n = 1-6)] are selected as prototype models to understand the interfacial interactions and proton transfer mechanism between a carbonaceous surface and water molecules. The excess protons can localize in the vicinity of the hydrophobic-hydrophilic interface, and these clusters are stabilized by various kinds of noncovalent interactions. Calculations are carried out using ab initio (MP2) and density functional theory B3LYP methods to shed more light on geometries, energetics, and spectral signatures of the protonated species [H+(H2O)n] at the interfaces. These calculations revealed few low-lying isomers, which have not been reported earlier. Scrutiny of the results reveals that proton localization in the hydrophilic environment is more stable than the hydrophobic benzene π-cloud. Furthermore, the occurrence of an O-H+···π hydrogen bond significantly influences the O-H+···O interactions in the water clusters and also intensively affects the vibrational modes of the Eigen cation. Thus, the aromatic π-clouds can stabilize the Eigen cation and at the same time, a twisted form of Eigen (one O-H+···π → two O-H+···π) can enhance the proton transfer through the water chain via a Grotthuss-type mechanism. The vibrational spectra of these clusters reveal that there is a large red-shifted frequency for the O-H+···O, O-H+···π, and O-H···π modes of interaction. The energetic values and vibrational frequencies obtained from the B3LYP method are in close agreement with the MP2 level and experimental values, respectively.

Density Functional Theory Studies on Zeolitic Imidazolate Framework-8 and Ionic Liquid-Based Composite Materials.

The identification of suitable density functional methods for predicting the properties of nanoporous composite materials is highly significant in the field of chemical and material sciences. The stability of the composite materials depends on the nature of bonding and dispersive interaction at the interface. Thus, we have studied the effect of dispersion correction in the incorporation of hydrophobic and hydrophilic ionic liquids (ILs) into zeolitic imidazolate framework-8 (ZIF-8) nanostructures using the density functional theory (DFT)-based approaches. These structures were analyzed employing selected methods (Becke-Lee-Yang-Parr and Perdew-Burke-Ernzerhof) with dispersion correction (D2 or D3) and different basis sets (such as double-zeta valence polarized (DZVP), triple-zeta valence polarized (TZVP), and triple-zeta valence doubly polarized (TZV2P)) for the understanding of microscopic features of IL@ZIF-8 nanopores. It is found that the result obtained from DFT-D2/TZVP is more reliable for the prediction of the experimental crystal structure as well as stability and spectral information of the complexes. Furthermore, the microscopic analysis of geometries reveals that ILs are highly dispersed and stabilized at the nanopores of ZIF-8, particularly the ZIF-8 structure is highly preferable for the hydrophobic group in ILs. It is found that fluorine-containing anions are highly dispersed on the ZIF-8 surface compared to the nonfluorinated anion (i.e., [BMIM]+[Cl]-). This is confirmed from the adsorption energies (E ads), charge transfer, electron density analyses, and IR spectral analysis. These findings can provide more insights into the stability of composite materials, which are suitable for applications of catalytic conversion at the confined state, gas storage, and separation techniques.