Experimental and theoretical study on the hydrogen bonding between dopamine hydrochloride and N,N-dimethyl formamide

The Role of Antisolvents with Different Functional Groups in the Formation of Cs4PbBr6 and CsPbBr3 Particles

Compared to the high-temperature hot injection (HI) technique, the room-temperature supersaturated recrystallization (SR) approach is more hopeful to realize the industrialized production of CsPbX3 (X = Cl, Br, and I) nanomaterials. However, accurate compositional control of the product is still difficult, and the role and underlying mechanism of antisolvents in the reprecipitation process remain unclear. Herein, CsPbBr3 particles and CsPbBr3/Cs4PbBr6 composites with certain proportions are synthesized using different antisolvents with the SR method. By adjustment of the polarity or functional group of antisolvents, it is found that the functional groups of antisolvents have a major impact on the composition of the products. Furthermore, the influential mechanism of different antisolvents on the compositions of products is investigated by combining electrostatic potential calculations and ultraviolet-visible absorption spectroscopy. It suggests that the interaction between functional groups of antisolvents and organic ligands influences the coordination status of the intermediate Pb-complex and further affects the separating rate of the Pb(II)-intermediate, leading to the formation of products with different compositions. A physicochemical mechanism is proposed to explain the formation of Cs4PbBr6 and CsPbBr3. This work deepens the understanding of the formation mechanism of all-inorganic metal halide perovskite-related materials based on the SR method and provides new routes to achieve their controllable preparation.

Size-Dependent Electrochemistry of Oxygenated Ti3 C2 Tx MXenes

2D MXenes are widely proved to be potential electrode materials, although the size effect on their electrochemistry is not fully understood. In this work, Ti₃ C₂ T_x nanoflakes are prepared through acidic etching of Ti₃ AlC₂ powders, followed by the intercalation treatment with tetrapropylammonium hydroxide. Such a method produces large-scale delaminated and oxygenated nanoflakes. With aid of centrifugation, the nanoflakes with varied lateral sizes and thicknesses are collected, where electrochemical response of charged redox probes and polar phenol molecules is varied. Density functional theory and energy dispersive spectroscopy confirm such electrochemical response is dependent on the size and thickness of used nanoflakes, more exactly the oxygen content on their surface. Taking the nanoflakes obtained using a centrifugal speed of 5000 rpm (MX-TPA_0.2 ) as an example, they feature good dispersibility, a high oxygen content, a small size, and a thin thickness. On these nanoflakes electrochemical response of polar p-substituted phenols is pronounced, stemming from a strong electron-withdrawing interaction of their oxygenated termination with the Ar-OH. A sensitive electrochemical sensor is further constructed for the detection of p-nitrophenol. This work thus provides an approach to synthesize MXenes with different sizes and thicknesses as well as further to reveal size-dependent electrochemistry of MXenes.

Experimental and Theoretical Study on the Interaction of P-Aminophenol Hydrochloride with H2O

UV-Vis absorption spectra, cyclic voltammetry and 1H nuclear magnetic resonance (1H NMR) spectra were applied to explore the hydrogen bond interactions of p-aminophenol hydrochloride (PAH) with H2O. The results indicated the hydrogen bonds were formed in PAH–H2O system. The anodic/cathodic peak potentials and UV-Vis absorption bands of PAH in H2O could be affected due to the interactions. The results of density functional theory, atoms in molecules theory and natural bond orbital analyses further confirmed the existence of hydrogen bonds between the phenolic hydroxyl, –NH3 + protons and Cl− of PAH and H2O. Furthermore, the π-π stacking was suggested between PAH benzene rings from the 1H NMR spectra at higher concentrations.

Hydrogen Bond Interaction of Ascorbic Acid with Urea: Experimental and Theoretical Study

The interactions of ascorbic acid (AA) with urea were investigated by using the cyclic voltammetry, density functional theory, atoms in molecules and natural bond orbital analyses. The experimental and theoretical results show that the hydrogen bonds are formed between AA and urea, wherein the mainly interaction sites are the hydrogen atoms on enediol of AA and the oxygen atom on carbonyl of urea. The electrochemical behavior of AA was significantly affected by above interactions.

Hydrogen bonding and π-π stacking in nicotinamide/H2O mixtures

The interactions between nicotinamide (NA) and H₂O were studied using UV-visible spectra (UV-Vis), cyclic voltammetry (CV), nuclear magnetic resonance (NMR), density functional theory (DFT) and atoms in molecules (AIM) analysis. According to the changes of the UV-Vis spectra and the oxidation and reduction potentials in cyclic voltammograms of NA in aqueous solution, it was found that hydrogen bonding occurred between NA and H₂O molecules. Quantum chemistry calculations and AIM analysis further confirmed the existence of hydrogen bonding between H₂O molecules and the amide group, the nitrogen atom, and hydrogen atoms on the pyridine ring of NA molecules. In addition, the NMR results demonstrated that the π-π stacking between NA pyridine rings could be formed at higher concentrations.

Detection of Dopamine by a Biomimetic Electrochemical Sensor Based on Polythioaniline-Bridged Gold Nanoparticles

A new biomimetic electrochemical sensor was developed for the detection of dopamine based on a glassy carbon electrode modified with electrochemically generated gold nanoparticles. The preparation of the polymer is simple and cost-effective, achieving the polymerization of thioaniline and generation of gold nanoparticles in a single step by cyclic voltammetry, in the presence of the target molecule, dopamine. After extraction, the imprinted polymer exhibits high sensitivity and selectivity for dopamine. Moreover, the developed imprinted polymer film allows the fast, direct detection of dopamine without the need of a redox mediator. The formation of a self-assembled monolayer of the monomer prior to electropolymerization ensures the adherence of the film onto the electrode surface, conferring good stability to the sensor (over two weeks). Cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used for the complete characterization of the developed sensor, and differential pulse voltammetry was used for its testing.