χ(3) scattering noises in nonlinear optical phase conjugation

Phase conjugation by Four-Wave Mixing (FWM) is treated quantum mechanically as a multiphoton scattering process. The spontaneous scattering of two counter-propagating photons gives rise to a background noise, whereas the stimulated scattering in the presence of the probe beam generates the phase conjugate signal. In addition, the stimulated scattering also contributes to a background noise which has never been discussed. Compared with Rayleigh scattering noise, the ⁽³⁾ scattering noises are relatively small for intensity up to 10⁸ W/cm². For higher intensities, the ⁽³⁾ scattering noises, in conjunction with the Rayleigh scattering noise, will affect the spatial fidelity of the optical phase conjugation.     

Biocompatible bacteria@Au composites for application in the photothermal destruction of cancer cells

We have successfully transformed the infectious E. coli bacteria into biocompatible bacteria@Au composites for photothermal therapy.     

Calculating molecular vibrational spectra beyond the harmonic approximation

We present a new approach for calculating anharmonic corrections to vibrational frequency calculations. The vibrational wavefunction is modelled using translated Hermite functions thus allowing anharmonic effects to be incorporated directly into the wavefunction whilst still retaining the simplicity of the Hermite basis. We combine this new method with an optimised finite-difference grid for computing the necessary third and fourth nuclear derivatives of the energy. We compare our combined approach to existing anharmonic models—vibrational self-consistent field theory (VSCF), vibrational perturbation theory (VPT), and vibrational configuration interaction theory (VCI)—and find that it is more cost effective than these alternatives. This makes our method well-suited to computing anharmonic corrections for frequencies in medium-sized molecules. Contribution of the Mark S. Gordon 65th Birthday Festschrift Issue.     

Quantum Mechanical Calculations for Biomass Valorization over Metal-Organic Frameworks (MOFs)

Metal-organic framework (MOF) in biomass valorization is a promising technology developed in recent decades. By tailoring both the metal nodes and organic ligands, MOFs exhibit multiple functionalities, which not only extend their applicability in biomass conversion but also increase the complexity of material designs. To address this issue, quantum mechanical simulations have been used to provide mechanistic insights into the catalysis of biomass-derived molecules, which could potentially facilitate the development of novel MOF-based materials for biomass valorization. The aim of this review is to survey recent quantum mechanical simulations on biomass reactions occurring in MOF catalysts, with the emphasis on the studies of the catalytic activity of active sites and the effects of organic ligand and porous structures on the kinetics. Moreover, different model systems and computational methods used for MOF simulations are also surveyed and discussed in this review.     

Effect of a charged boundary on electrophoresis in a Carreau fluid: a sphere at an arbitrary position in a spherical cavity

The influence of a charged boundary on the electrophoretic behavior of an entity in a non-Newtonian fluid is studied by considering a sphere at an arbitrary position in a spherical cavity filled with a Carreau fluid under the conditions of low surface potential and weak applied electric field. The dependence of the mobility of a sphere on its position in a cavity, the size of a cavity, the thickness of a double layer, and the nature of a fluid is investigated. In addition to the fact that the effect of shear-thinning is advantageous to the movement of a sphere, several other interesting results are also observed. For instance, if an uncharged sphere is in a positively charged cavity, where the electroosmotic flow and the induced charge on the sphere surface play a role, the effect of shear-thinning is important only if the thickness of the double layer is either sufficiently thin or sufficiently thick. However, this might not be the case if a positively charged sphere is in an uncharged cavity.     

Porous iron oxide based nanorods developed as delivery nanocapsules

A low-temperature solution approach (90-95 degrees C) using FeCl(3) and urea was carried out to synthesize beta-FeOOH nanorods in aqueous solution. The as-synthesized beta-FeOOH nanorods were further calcined at 300 degrees C to form porous nanorods with compositions including both beta-FeOOH and alpha-Fe(2)O(3). The derived porous nanorods were engineered to assemble with four layers of polyelectrolytes (polyacrylic acid (PAA)/polyethylenimine(PEI)/PAA/PEI) on their surfaces as polyelectrolyte multilayer nanocapsules. Fluorescein isothiocyanate (FITC) molecules were loaded into the polyelectrolyte multilayer nanocapsules in order to investigate drug release and intracellular delivery in Hela cells. The as-prepared nanocapsules showed ionic strength-dependent control of the permeability of the polyelectrolyte shells. The release behavior of the entrapped FITC from the FITC-loaded nanocapsules exhibited either controlled- or sustained-release trends, depending on the compactness of the polyelectrolyte shells on the nanorod surfaces. Cytotoxicity measurements demonstrate that the native nanorods and the polymer-coated nanorods have excellent biocompatibility in all dosages between 0.1 ng mL(-1) and 100 microgm L(-1). The time dependence of uptake of FITC-loaded nanocapsules by Hela cancer cells observed by laser confocal microscopy indicates that the nanocapsules can readily be taken up by cancer cells in 15 min, a relatively short period of time, while the slow release of the FITC from the initial perimembrane space into the cytoplasm was followed by release into the nucleus after 24 h.     

Effect of a charged boundary on electrophoresis: a sphere at an arbitrary position in a spherical cavity

The effect of the presence of a charged boundary on the electrophoretic behavior of a particle is investigated by considering a sphere at an arbitrary position in a spherical cavity under conditions of low surface potential and weak applied electric field. Previous analyses are modified by using a more realistic electrostatic force formula and several interesting results, which are not reported in the literature, are observed. We show that the qualitative behavior of a particle depends largely on its position, its size relative to that of a cavity, and the thickness of the electric double layer. In general, the presence of a cavity has the effect of increasing the conventional hydrodynamic drag on a particle through a nonslip condition on the former. Also, a decrease in the thickness of the double layer surrounding a sphere has the effect of increasing the electrostatic force acting on its surface so that its mobility increases. However, this may not be the case when an uncharged particle in placed in a positively charged cavity, where the electroosmotic flow plays a role; for example, the mobility can exhibit a local maximum and the direction of electrophoresis can change.     

Synthesis and characterization of 1,3,4‐oxadiazole‐triazolopyridinone hybrid derivatives as new blue‐greenish photoluminescent materials

Recently, New functionalized oxadiazole‐triazolopyridinone hybrid compounds were investigated as photoluminescent materials. In this work, we introduce triazolopyridinone to synthesize a series of oxadiazole‐triazolopyridinone hybrid derivatives as potential photoluminescent materials and explore the effect of modification of the triazolopyridinone moiety. The λ_max values of the photoluminescence (PL) spectra of 1,3,4‐oxadiazole‐triazolopyridinone hybrids are promoted to longer wavelengths (470‐486 nm) than the traditional 1,2,3‐triazole derivatives (410‐425 nm) in solutions. PL spectra 5a, 5d , and 5g of the vacuum evaporated films on quartz substrates, with a maximum at 487 nm, shows a red‐shift (～15‐20 nm), with respect to the solution spectrum. The solution fluorescence quantum yields (Φ_f) were measured, all of which fell into the range 0.65‐0.76, and were determined relative to that of 2‐phenyl‐5‐(4‐biphenyl)‐1,3,4‐oxadiazole in benzene (Φ_f = 0.80). 1,3,4‐Oxadiazole‐triazolopyridinone hybrid derivatives show clearly non‐reversible reduction processes in cyclic voltammogram measurements. Following spectroscopic studies and observation of the electrochemical behaviors, 1,3,4‐oxadiazole‐triazolopyridinone derivatives were determined to be potential efficient bluegreenish photoluminescent materials.