Polyphenylenepyridyl dendrimers as stabilizing and controlling agents for CdS nanoparticle formation

Semiconductor nanoparticles (NPs) are being actively explored for applications in medical diagnostics and therapy and numerous electronic devices including solar cells. In this paper we demonstrate the influence of the third generation rigid polyphenylenepyridyl dendrimers (PPPDs) of a different architecture on the formation of well-defined CdS NPs. A high temperature approach to the synthesis of novel CdS/PPPD nanocomposites is feasible due to the high thermal stability of PPPDs. The PPPD architecture affects the CdS NP formation: larger NPs are obtained in the presence of dendrimers with 1,3,5-triphenylbenzene cores compared to those with tetrakis(4-ethynylphen-1-yl)methane cores. The reaction conditions such as concentrations of PPPDs and NP precursors and the temperature regime also influence the CdS NP sizes. For the first time, we elucidated a mechanism of CdS NP formation in a non-coordinating solvent through the CdO redispersion in the presence of PPPDs. Interesting optical properties of these CdS/PPPD nanocomposites make them promising candidates for imaging applications.     

Development of nanoimprinted InP QDs decorated polyaniline solar cell with conversion efficiency 3%

Organic–inorganic hybrid materials received considerable attention due to promising industrial applications. The originality of novel chemical recipes, allowing incorporation of well-defined nanoparticle structures into complex hybrid architectures, opens new possibilities for multidisciplinary fields and in particular in optoelectronic devices. The rate of non-radiative recombination and energy transfer through a hybrid inorganic/organic nanocomposite is mainly governing the ability of charge transfer from semiconductor quantum dots to conjugated polymers. Herein, we report that the electron–hole non-radiative recombination in polymer can be constricted by funneling the diffusion of exciton by engineering a proper morphology of a hybrid nanostructure. InP quantum dots have been selected due to their efficient exciton generation and polyaniline as a conjugated polymer for its potency to suppress non-radiative recombination by restraining exciton diffusion. The hole transfer was monitored via bi-exponential kinetic model and time of flight method. The conversion efficiency of the prepared films increased from 0.23% to 3.1% when the thickness is increased from 14 nm to 157 nm.     

ION EXCHANGE PROPERTIES OF THE SULFUR-MODIFIED BIOTITE

ABSTRACT

The ion exchange behavior of a sulfur-modified biotite towards Pb²⁺, Hg²⁺, Co²⁺, Cu²⁺, Cd²⁺ and Zn²⁺ ions has been studied. The ion exchange isotherms of divalent cations were determined and concentration equilibrium constants as a function of metal loading were analyzed. Sulfur modified biotite exhibits high affinity for Hg²⁺, Pb²⁺, Cu²⁺ and Cd²⁺ ions in individual solutions and in the presence of electrolytes. About 200 mg Hg/g uptake in 1·10^?3 M Hg²⁺ solution and ～ 35 mg Hg/g in groundwater simulant or an alkaline simulant 2 M in NaN0₃ + 1 M in NaOH was found. The possibility of a complex ion exchange and precipitation mechanism of the sulfur modified biotite towards the soft cations is proposed.     

SYNTHESIS AND CHARACTERIZATION OF THE ION EXCHANGE PROPERTIES OF A SPHERICALLY GRANULATED SODIUM ALUMINOPHOSPHATESILICATE

ABSTRACT

Spherically granulated sodium aluminosilicophosphate (APS) of the empirical formula Na₄Al₄PS₁₈O_46.5 18H₂O was synthesized by a gel method. The APS was characterized by elemental analysis, X-ray diffraction, TGA and ²⁷AI, ²⁸Si and ³¹P MAS NMR spectroscopy methods. Ion exchange of alkali, alkaline earth and some other divalent metal cations by APS was studied in batch conditions. It was found that the APS has a cation exchange capacity of 2.5 meq/g and exhibits rapid kinetics of ion exchange. The ion exchange isotherms of alkali, alkaline earth and some other divalent cations were determined and the corrected selectivity coefficients as a function of metal loading were analyzed. It was found that APS exhibits a high affinity for cesium ion, a moderate affinity for some heavy metal cations (Pb²⁺, Zn⁺) and a low affinity for alkali and alkaline earth metal ions. A testing of the APS in complex solutions suggests that it could be a promising exchanger for treatment of some specific nuclear waste and contaminated environmental and biological liquors from radioactive cesium and toxic heavy metal ions.     

Ion Exchange Behavior of the NH4TiOPO4 Based Exchanger

ABSTRACT

Several compounds of the general formula (NH₄)_(1?x)H_xTiOPO₄·nH₂O (x=0.45-0.75) were prepared by acid treatment of ammonium titanyl phosphate (NTP) at elevated temperature (80-90^°C). The protonic phases of the NTP were characterized by elemental analysis, TGA, FT-IR, MAS ³¹P NMR and X-ray diffraction. Their ion exchange behavior towards alkali, alkaline earth and some transition metal ions in pure single ion solutions and mixtures was studied. A high capacity and selectivity for potassium and lead makes it promising for certain types of waste treatment and selected analytical separations.     

Screening for biohydrogen production by cyanobacteria isolated from the Baltic Sea and Finnish lakes

Cyanobacteria are the only bacteria capable of performing oxygenic photosynthesis in which they harness solar energy and convert it into chemical energy stored in carbohydrates. Under specific conditions, cyanobacteria can use solar energy to produce also molecular hydrogen.     

Antistress Action of Melanocortin Derivatives Associated with Correction of Gene Expression Patterns in the Hippocampus of Male Rats Following Acute Stress

Natural melanocortins (MCs) have been used in the successful development of drugs with neuroprotective properties. Here, we studied the behavioral effects and molecular genetic mechanisms of two synthetic MC derivatives-ACTH(4–7)PGP (Semax) and ACTH(6–9)PGP under normal and acute restraint stress (ARS) conditions. Administration of Semax or ACTH(6–9)PGP (100 μg/kg) to rats 30 min before ARS attenuated ARS-induced behavioral alterations. Using high-throughput RNA sequencing (RNA-Seq), we identified 1359 differentially expressed genes (DEGs) in the hippocampus of vehicle-treated rats subjected to ARS, using a cutoff of >1.5 fold change and adjusted p-value (Padj) < 0.05, in samples collected 4.5 h after the ARS. Semax administration produced > 1500 DEGs, whereas ACTH(6–9)PGP administration led to <400 DEGs at 4.5 h after ARS. Nevertheless, ~250 overlapping DEGs were identified, and expression of these DEGs was changed unidirectionally by both peptides under ARS conditions. Modulation of the expression of genes associated with biogenesis, translation of RNA, DNA replication, and immune and nervous system function was produced by both peptides. Furthermore, both peptides upregulated the expression levels of many genes that displayed decreased expression after ARS, and vice versa, the MC peptides downregulated the expression levels of genes that were upregulated by ARS. Consequently, the antistress action of MC peptides may be associated with a correction of gene expression patterns that are disrupted during ARS.     

Effect of Mode Transformation in THz Clinotron

Extension of the theory of a clinotron is developed by use of the scattering matrix of an oversized T-junction on the ends of a slow wave system. The matrix contains elements corresponding to the transformation of slow grating modes into fast ones and vice versa. Those fast waves with low ohmic losses provide strong resonant properties of a clinotron even in the case of strong attenuation of the surface mode. Results of the theoretical simulation are compared with experimental ones and obtained dependencies explain strong resonances in sub-THz clinotrons.     

Efficient All-Perovskite White Light-Emitting Diodes Made of In Situ Grown Perovskite-Mesoporous Silica Nanocomposites

Metal halide perovskite quantum dots (QDs) have emerged as potential materials for high brightness, wide color gamut, and cost-effective backlight emission due to their high photoluminescence quantum yields, narrow emission linewidths, and tunable bandgaps. Herein, CsPbX₃/SBA-15 nanocomposites are prepared with outstanding optical properties and high stability through an in situ growth strategy using mesoporous silica particles. According to finite-difference time-domain simulations, the mesoporous structure provides a strong waveguide effect on perovskite QDs and the uniform dispersion suppresses reabsorption losses, improving the overall photoconversion efficiency of perovskite QDs. The as-fabricated perovskite monochromatic light-emitting diode (LED) has a maximum luminous efficiency of 183 lm W⁻¹, which is the highest for monochromatic perovskite LEDs reported to date. A further benefit of this work is that the white devices, which combine the green and red perovskite nanocomposites with commercial blue LED, exhibit a high luminous efficiency of 116 lm W⁻¹ and a wide color gamut (125% for NTSC and 94% for Rec. 2020) with coordinates of (0.33,0.31).