Organic light-emitting diodes (OLEDs) have become one of the most popular lighting technologies since they offer several advantages over conventional devices. In carbazole-benzophenone (CzBP) OLED devices, the polymeric form of the compound is previously reported to be Thermally Activated Delayed Fluorescence (TADF)-active (∆EST ≈ 0.12 eV), while the monomer (CzBP) (∆EST ≈ 0.39 eV) does not. The present study examines the effects of chemical tailoring on the optical and photophysical properties of CzBP using DFT and TDDFT methods. The introduction of a single – NO2 group or di-substitution ( – NO2 , – COOH or – CN) in the selected LUMO region of the reference CzBP monomer significantly reduces ∆EST ≈ 0.01 eV, projecting these systems as potential TADF-active emitters. Furthermore, the chemical modification of CzBP-LUMO alters the two-step TADF mechanism (T1 → T2 → S1 ) in CzBP (ES1 > ET2 > ET1 ) to the Direct Single Harvest (T1 → S1 ) mechanism (ET2 > ES1 > ET1 ), which has recently been identified in the fourth-generation OLED materials.

PaDADH is an amine oxidase that catalyzes the conversion of D-arginine into iminoarginine. The authors formulate computational models based on the ONIOM method to elucidate the oxidation mechanism of D-arginine into iminoarginine using the crystal structure of the enzyme complexed with iminoarginine. The calculations show that the deprotonation step occurs prior to the hydride transfer step, and active site water molecule(s) may have participated in the deprotonation process.

Abstract

D-Arginine dehydrogenase from Pseudomonas aeruginosa (PaDADH) is an amine oxidase which catalyzes the conversion of D-arginine into iminoarginine. It contains a non-covalent FAD cofactor that is involved in the oxidation mechanism. Based on substrate, solvent, and multiple kinetic isotope effects studies, a stepwise hydride transfer mechanism is proposed. It was shown that D-arginine binds to the active site of enzyme as α-amino group protonated, and it is deprotonated before a hydride ion is transferred from its α-C to FAD. Based on a mutagenesis study, it was concluded that a water molecule is the most likely catalytic base responsible from the deprotonation of α-amino group. In this study, we formulated computational models based on ONIOM method to elucidate the oxidation mechanism of D-arginine into iminoarginine using the crystal structure of enzyme complexed with iminoarginine. The calculations showed that Arg222, Arg305, Tyr249, Glu87, His 48, and two active site water molecules play key roles in binding and catalysis. Model systems showed that the deprotonation step occurs prior to hydride transfer step, and active site water molecule(s) may have participated in the deprotonation process.

We present quantum structure calculations aimed at demon- strating the possible existence of dipole-bound states (DBS) for the anion C5N−, a species already detected in the Inter- stellar medium (ISM). The positive demonstration of DBS existence using ab initio studies is an important step to- ward elucidating possible pathways for the formation of the more tightly bound valence bound states (VBS) in envi- ronments where free electrons from starlight ionization pro- cesses are known to be available to interact with the radical partner of the title molecule. Our current calculations show that such DBS states can exist in C5N−, in agreement with what we had previously found for the smaller cyanopolyyne in the series: the C3N− anion. The predicted binding en- ergies which we found are 3 and 9 cm−1 for the 1Σ+ and 3Σ+ DBS, respectively. Furthermore, equilibrium geome- tries, equilibrium rotational constants, electric dipole mo- ments, and relative electronic energies were determined for the ground anion X1Σ+ and the two lowest electronic states of the parent neutral, X2Σ+ and A2Π.

Core-shell nanostructures of silicon oxide@noble metal have drawn a lot of interest due to their distinctive characteristics and minimal toxicity with remarkable biocompatibility. Due to the unique property of localized surface plasmon resonance (LSPR), plasmonic nanoparticles are being used as surface-enhanced Raman scattering (SERS) based detection of pollutants and photothermal (PT) agents in cancer therapy. Herein we demonstrate the synthesis of multifunctional silica core - Au nanostars shell (SiO2@Au NSs) nanostructures using surfactant free aqueous phase method. The SERS performance of the as-synthesized anisotropic core-shell NSs was examined using Rhodamine B (RhB) dye as a Raman probe and resulted in strong enhancement factor of 1.37 × 106. Furthermore, SiO2@Au NSs were also employed for PT killing of breast cancer cells and they exhibited a concentration-dependent increase in the photothermal effect. The SiO2@Au NSs show remarkable photothermal conversion efficiency of up to 72% which is unprecedented. As an outcome, our synthesized NIR active SiO2@Au NSs are of pivotal importance to have their dual applications in SERS enhancement and PT effect.

This study involves the preparation and catalytic properties of anatase titanium dioxide nanofibers (TiO2 NFs) supported gold nanoparticles (Au NPs) using a model reaction based on the reduction of 4-nitrophenol (NP) into 4-aminophenol (AP) by sodium borohydride (NaBH4). The fabrication of surfactant-free Au NPs was performed using pulsed laser ablation in liquid (PLAL) technique. The TiO2 NFs were fabricated by a combination of electrospinning and calcination process using a solution containing poly(vinyl pyrolidone)(PVP) and titanium isopropoxide. The adsorption efficiency of laser-generated surfactant-free Au NPs to TiO2 NF supports as a function of pH was analyzed. Our results show that the electrostatic interaction mainly controls the adsorption of the nanoparticles. Au NPs/TiO2 NFs composite exhibited good catalytic activity for the reduction of 4-NP to 4-AP. The unique combination of these materials leads to the development of highly efficient catalysts. Our heterostructured nanocatalysts possibly form an efficient path to fabricate various metal NP/metal-oxide supported catalysts. Thus the applications of PLAL-noble metal NPs can widely broaden.