A Dual-Readout Method for Biothiols Detection Based on the NSET of Nitrogen-Doped Carbon Quantum Dots–Au Nanoparticles System

In this paper, a rapid, simple and highly sensitive method with dual-readout (colorimetric and fluorometric) based on the nanometal surface energy transfer (NSET) between nitrogen-doped carbon quantum dots (NCQDs) and gold nanoparticles (AuNPs) for detection of biothiols is described. Highly luminescent NCQDs were prepared via a simple one-step hydrothermal method by applying sucrose and glycine as carbon and nitrogen sources. The results showed the obtained NCQDs had an average particle diameter of 5 nm and highly luminescent. The maximum emission wavelength was 438 nm with an excitation wavelength of 360 nm. In this system, NCQDs and AuNPs were respectively treated as energy donors and energy acceptors, which enable the nanometal surface energy transfer (NSET) from the NCQDs to the AuNPs, quenching the fluorescence. However, biothiols was used as a competitor in the NSET by the strongly Au-S bonding to release NCQDs from the Au surface, which subsequently produces fluorescent signal recovery and the red-to-purple color change quickly. This probe showed rapid response, high selectivity and sensitivity for biothiols with dual colorimetric and fluorescent turn-on signal changes. The low detection limit was calculated as 20 nM by using L-cysteine acted as target melocules. The method was also successfully applied to the determination of biothiols in human serum samples, and the results were satisfying.     

Holstein–Primakoff (H-P) Approach to Determine the Optical Response of Hybrid Optomechanical System Containing Multiple Quantum Dots

A theoretical model is presented to study the hybrid optomechanical system comprising an ensemble of N number of quantum dots (QDs). Utilizing the Holstein–Primakoff (H-P) transformation formalism, the calculations become easily scalable. The bistability in this hybrid optomechanical system is studied in the presence of third order nonlinear χ⁽³⁾ medium using the H-P transformation method and to verify the results, numerical method has also been utilized. It is also demonstrated that the system's parameters may be tuned to alter the bistability phenomenon and absorption spectrum's response, which exhibits both positive and negative absorption (emission). This alternative approach (H-P transform) is demonstrated to solve analytically the system containing multiple QDs in an elegant manner.     

A New Strategy to Design Photostable Luminescent Materials Based on Lanthanide(III) β-Diketonate Complexes for Advanced Photonic Applications

Optics and Spectroscopy - An analysis of the prospects for creating new luminescent molecular photonics materials based on mesogenic lanthanide(III) β-diketonate complexes is presented. We...     

Phase Formation Initiated by Irradiation of the Film (Si) – Substrate (Grade 3 Steel) System with a High-Intensity Pulsed Electron Beam

Russian Physics Journal - The physical principles of formation of phase composition and defect substructure of a surface alloy in a low-stability state formed as a result of irradiation of the film...     

Change in the Absorption Spectra of Membranes Containing Co(III)‐ and Sn(IV) Tetraphenyl Porphyrins as a Result of the Use of Anion‐Selective Electrodes Based on Them

Electronic absorption spectra of the components of the membranes of anionselective electrodes containing Co(OH) and Sn(OH) Sn(OH)₂ tetraphenyl porphyrins (TPP) as electroactive substances and various softeners and lipophilic ionic additives have been investigated. 2Nitrophenyloctylic ether, bromonaphthalene, dibutyl phthalate, and dioctyl phthalate were used as softeners; tetradecyl ammonium nitrate and tetrakis(4chlorophenyl)potassium borate were used as ionic additives. To investigate the electronic absorption spectra, we dissolved the membranes in cyclohexane at different pH before and after their use. The influence of the acidity and the nature of a softener on the position and intensity of the absorption bands of metalloporphyrin in a membrane is discussed. It is shown that the use of membranes containing Co(OH)TPP in highly acidic media is accompanied by its demetallation and the formation of protonized forms of TPP. The membranes based on Sn(OH)₂TPP are more stable in acid media.     

Effect of Oxygen on the Quantum,Magnetic, and Thermodynamic Properties of Co Nanowires on the Reconstructed Anisotropic (1 × 2)/Au(110) and (1 × 2)/Pt(110) Surfaces: Ab Initio Approach

Ab initio theoretical study of the quantum magnetic properties of Co nanowires on the pure and oxygen-reconstructed (1 × 2)/Au(110) and (1 × 2)/Pt(110) surfaces is performed. Their structures and electronic configurations are calculated using the electron density functional theory. High values of magnetic moment and magnetic anisotropy energies of Co atoms are found on both pure and oxygen-reconstructed (1 × 2)/Au(110) and (1 × 2)/Pt(110) surfaces. The adsorption of oxygen atoms on the (1 × 2)/Au(110) substrate is shown to affect the structural arrangement of Co nanowire atoms on this substrate and to increase the magnetic anisotropy energy (by 1.91 meV per nanowire atom). The adsorption of oxygen on the Pt(110) substrate substantially decreases the magnetic anisotropy energy of the Co nanowire on it (by 5.98 meV per atom). The origin of these changes is revealed by analyzing the local densities of states of the d electrons of nanowire atoms. The temperature ranges of the states with the lowest free surface energy are determined using the atomistic thermodynamics methods. These data and the available experimental data are used to predict the possibility of observing the structures under study in experiments.     

Tautomerization and solvent effects on the absorption and emission properties of the Schiff base N,N′-bis(salicylidene)-p-phenylenediamine – A TDDFT study

Time-dependent density functional theory combined with a polarized continuum model has been applied to study solvent effects on the geometrical and energetic properties, as well as the absorption and emission properties, of three tautomeric forms of N,N′-bis(salicylidene)-p-phenylenediamine (BSP). The calculated properties are in agreement with the available experimental data. It was observed that the solvent environment does not affect the vertical excitation energies significantly, whereas tautomerization strongly affects both the absorption and emission spectra of BSP.     

Influence of Aprotic Solvents on the Transmission of Anomalous Substituent Effects on 13C NMR Chemical Shifts at the Carboxyl Carbon (δco) in Meta-Substituted Benzoic Acids: A Strong Evidence for π-Polarization Mechanism

Anomalous (reverse) substituent-induced ¹³C nuclear magnetic resonance chemical shifts at the carboxyl carbon (δ_co) in meta-substituted benzoic acids have been studied for 11 substituents having varying electronic effects in 4 aprotic (nonhydroxylic) solvents of varying polarity by employing different dual substituent parameter models. The regression results for apolar aprotic solvents provide a strong evidence for through space π-polarization mode of transmission of reverse meta-substituent effects on the carboxyl carbon in benzoic acids. The results for dipolar aprotic solvents indicate significant specific solvation of π-polarized forms of the acids. The study showed further that an apolar aprotic solvent has a distinct preference over a dipolar aprotic one for investigating intrinsic substituent effects on chemical shifts in aromatic molecules.     

Interference Angle on Quantum Rotational Energy Transfer in Na+Na2 (A1 Σ+u,v=8∽ b3 Π0u,v=14) Molecular Collision System

In order to study the collisional quantum interference (CQI) on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Na+Na₂ (A¹Σ^+_u, v=8∽b³Π_0u, v=14) collision system. In this paper, based on the first-Born approximation of time-dependent perturbation theory and takinginto accounts the anisotropic effect of Lennard-Jones interaction potentials,we present a theoretical model of collisional quantum interference inintramolecular rotational energy transfer, and a relationship betweendifferential and integral interference angles.     

A computational perspective on the kinetics and thermochemistry of the gas phase reactions of 1, 1-dichlorodimethylether (DCDME) with OH radical at 298 K

Kinetics and thermochemistry of the gas phase reactions between CH₃OCHCl₂ (DCDME) and OH radical are investigated theoretically. The geometries and all the stationary points on the potential energy surface are calculated at BHandHLYP/6-311G(d,p) method. The energy information is further refined at CCSD(T)/6-311G(d,p) level of theory. Reaction profiles are modelled including the formation of two pre-reactive and post-complexes. The rate constants, which are evaluated by Canonical Transition State Theory (CTST) including tunnelling correction at 298 K, are in very good agreement with the available experimental data. The percentage contributions of both reaction channels are also reported at 298 K. The hydrogen abstraction reaction from the –CHCl₂ group is found to be dominant leading to the formation of CH₃OCCl₂ + H₂O. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CH₃OCHCl₂, CH₃OCCl₂ and CH₂OCHCl₂ are also reported.     

Infrared and Mössbauer Spectral Studies on Some Tin(IV) Complexes: A Qualitative Correlitation with the Hard and Soft Acid-Base Theory

The principle of the hard and soft acid-base theory (HSAB) is that binding of hard acids with hard bases and soft acids with soft bases is preferred.¹ This implies that the maximum bond strength in a series of acid-base complexes should occur, all other factors being equal, where the degree of hardness or softness of the acid and base are most nearly matched. To test this hypothesis, we prepared a number of tin(IV) complexes of varying softness with the soft base 2,5-dithiahexane (CH₃SCH₂CH₂OCH₃, DTH) and the hard base 1,2-dimethoxyethane (CH₃OCH₂CH₂OCH₃, DME). The acids employed were SnCl₄, CH₃,SnCl₃, SnBr₄, and SnI₄. The complexes thus obtained were studied by infrared and Mcssbauer techniques in order to determine which, if any, of the complexes exhibited spectral details which could be correlated with HSAB.