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In this work, the photocatalytic hydrogen evolution from ammonia borane under near-infrared laser irradiation at ambient temperature was demonstrated by using the novel core-shell upconversion-semiconductor hybrid nanostructures (NaGdF4:Yb3+/Er3+@NaGdF4@Cu2O). The particles were successfully synthesized in a final concentration of 10 mg/mL. The particles were characterized via high resolution transmission electron microscopy (HRTEM), photoluminescence, energy dispersive X-ray analysis (EDAX), and powder X-ray diffraction. The near-infrared-driven photocatalytic activities of such hybrid nanoparticles are remarkably higher than that with bare upconversion nanoparticles (UCNPs) under the same irradiation. The upconverted photoluminescence of UCNPs efficiently reabsorbed by Cu2O promotes the charge separation in the semiconducting shell, and facilitates the formation of photoinduced electrons and hydroxyl radicals generated via the reaction between H2O and holes. Both serve as reactive species on the dissociation of the weak B-N bond in an aqueous medium, to produce hydrogen under near-infrared excitation, resulting in enhanced photocatalytic activities. The photocatalyst of NaGdF4:Yb3+/Er3+@NaGdF4@Cu2O (UCNPs@Cu2O) suffered no loss of efficacy after several cycles. This work sheds light on the rational design of near-infrared-activated photocatalysts, and can be used as a proof-of-concept for on-board hydrogen generation from ammonia borane under near-infrared illumination, with the aim of green energy suppliers. [ABSTRACT FROM AUTHOR]

Here we present a simple method to fill multiwalled carbon nanotubes (MWCNT) with silver. This method involves stirring of MWCTs in AgNO 3 solution at room temperature in open air followed by heating in H 2 atmosphere at 250 °C for two hours. Process also leads to small coating of Ag on the surface. We confirmed the presence of crystalline silver in both coating and filling in hybrid MWCNTs by high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction. After silver coating and filling, bulk thermal diffusivity and thermal conductivity of Ag hybrid MWCNTs were increased by 242% and 255%, respectively. Furthermore, current-voltage measurements using tuna probe in atomic force microscopy showed higher number of charge carriers in the Ag hybrid nanotubes compared to pristine MWCNTs which resulted in up to 173% increase in their electrical conductivity. The Ag hybrid MWCNT based sensor also showed rapid and reversible sensing for I 2 vapors: bulk sensor film demonstrated sensing response of 45% in just ~60 s at room temperature. However, the sensor recovery was slower: after removal of I 2 vapors source, the recovery took 400 s and required heating at 100 °C in air. Response and recovery of sensor film was maintained after repeated cycles of exposure. Finally, the Ag hybrid MWCNTs film displayed high stability and selectivity for I 2 vapors. [Display omitted] • Synthesis of Ag filled MWCNTs using a simple method • Bulk thermal conductivity of Ag hybrid MWCTs is 255% more than of MWCNTs. • Addition of Ag increases the bulk electrical conductivity of MWCNTs by 173%. • More negative charge carriers in the Ag hybrid MWCNTs than pristine MWCNTs • Ag hybrid MWCNTs showed rapid and reversible sensing for I 2 vapors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful crystallization of Ba 5 (PO 4) 3 OH:Er3+,Yb3+. • Enhanced upconverted visible emission by energy transfer from Yb3+ to Er3+. • Mechanisms of energy transfer from Yb3+ to Er3+. • Potential application of Ba 5 (PO 4) 3 OH:Er3+,Yb3+ in photodynamic therapy. Er3+-Yb3+ co-doped Ba 5 (PO 4) 3 OH nanoparticle powder phosphors were successfully synthesized by urea combustion method. The resulting powder phosphors were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). XRD data confirmed crystallization of pure hexagonal phase of Ba 5 (PO 4) 3 OH and HRSEM images showed formation of ellipsoidal particles. XPS data combined with EDS analysis confirmed the materials composition that corresponds with identification of all the chemical elements constituting the materials. The in vitro dark cytotoxicity of the particles confirmed lack of cytocidal behaviour in the absence of light, but considerable photodynamic therapy (PDT) activity was observed upon illumination. Upon excitation using a 980 nm laser, multiple emission peaks in the green and red regions corresponding to the optical transitions of Er3+ ion were observed. Upon co-doping with Yb3+, upconverted red emission was detected and this was attributable to non-radiative energy transfer from Yb3+ to Er3+. The proposed mechanism of upconversion photoluminescence is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The role of CNT in promoting crystallinity of composites. • Morphological and structural changes upon thermal treatment. • BiOI together with other phases enhanced photocatalytic activity. • BiOI/CNT composites showed higher photocatalytic activity for phenol and RhB. • Photocatalytic activity is dependent on synthesis, crystallinity and BiOI phases. In this work, we have prepared BiOI/CNT composites by hydrothermal method and studied the impact of CNT and hydrothermal treatment conditions (temperature and time) simultaneously on phenomena such as crystallization. The samples were studied using X-ray Diffraction (XRD), nitrogen sorption (Brunauer–Emmett–Teller (BET) specific surface areas), Scanning Electron Microscopy assisted with Energy Dispersive X-Ray spectroscopy (SEM-EDX), High Resolution Transmission Electron Microscopy (HRTEM), UV–vis Diffuse Reflectance spectroscopy (DRS), Raman spectroscopy and photoluminescence spectroscopy (PL). The different heat treatments applied and varied amount of CNT was found to have a profound effect on the structural, morphological, compositional and optical properties of the prepared composites. The distinguishable changes in the above-mentioned properties were clearly visible for the samples prepared at higher temperature and longer duration (150 °C, 6.30 h). Surprisingly, the presence of other phases of BiOI, such as Bi 7 O 9 I 3 , Bi 4 O 5 I 2 , Bi 5 O 7 I, also co-existed at the same time, although in low amount. Finally, for the study, the photocatalytic efficiency of the prepared samples was tested for phenol and RhB, as model pollutants, under visible light irradiation for 240 min and 120 min, respectively. The results revealed that the composites prepared at higher temperature with longer duration showed superior performance for the photodegradation of phenol and RhB. Additionally, the composites performed better than their respective reference samples in each case. Interestingly, the introduction of CNT promoted the crystallinity in the composites and promising results for the removal of phenol and RhB were achieved by the use of low power ordinary visible lamps. [ABSTRACT FROM AUTHOR]

In the present work, CaWO 4 /Ag 2 MoO 4 nanohybrid was synthesized by sono-chemical method. Fourier-transform infrared spectroscopy (FTIR), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDAX) and BET surface area analyzer were used to characterize the structure and optical properties of CaWO 4 /Ag 2 MoO 4 nanohybrid. The HRTEM image represents the formation of CaWO 4 /Ag 2 MoO 4 nanohybrid with clear facets and narrow size range. The XRD results showed that CaWO 4 /Ag 2 MoO 4 nanohybrid composed of combined phases of CaWO 4 and Ag 2 MoO 4. A red-shift was observed in the optical absorption of nanohybrid after loading Ag 2 MoO 4 on CaWO 4. The photodegradation of MB by CaWO 4 /Ag 2 MoO 4 nanohybrid (91.4%) showed excellent performance when compared with the pure Ag 2 MoO 4 (59.6%) and CaWO 4 (14.3%) under visible light. The scavenging test revealed that the key species responsible for the degradation of MB dye was hydroxide radical (•OH). The degradation of MB was well fitted to the pseudo-first-order kinetics with a high regression coefficient value (R2 > 0.95). The photostability and reusability of the nanohybrid was studied and the nanohybrid showed almost same degradation efficiency even at 6th cycle. The nanohybrid showed enhanced antimicrobial activity against Escherichia coli and Bacillus subtilis. Therefore, CaWO 4 /Ag 2 MoO 4 nanohybrid photocatalyst can be used as an effective candidate for environmental remediation through photocatalysis and bactericidal applications. • CaWO 4 /Ag 2 MoO 4 nanohybrid was synthesized by sonochemical method. • The CaWO 4 /Ag 2 MoO 4 nanohybrid can able to degrade 91.4% of MB dye in 180 min. • CaWO 4 /Ag 2 MoO 4 nanohybrid demonstrates good photocatalytic activity, photostability and antimicrobial activity. • The active species of photocatalytic activity of nanohybrid was due to the photogenerated hydroxide radicals. [ABSTRACT FROM AUTHOR]

• Guanine as a heterogeneous and recyclable base in the synthesis of novel spirooxindole compounds. • Usage of magnetic support for catalyst and its easy separation from the reaction medium. • synthesis of some novel spirooxindole compounds and highly substituted dihydro-2-oxopyrroles in aqueous media. • Recyclability and reusability of the catalyst up to ten times. Guanine stabilized on the surface of silica-modified magnetic nanoparticles, by the propyl group as a linker, (Fe 3 O 4 @SiO 2 -n-(propyl)-guanine), was prepared, identified and used as a recyclable base in the synthesis of novel spirooxindole compounds and highly substituted dihydro-2-oxopyrroles in aqueous media. Fe 3 O 4 @SiO 2 -n-(propyl)-guanine was characterized via some spectroscopic and microscopic techniques such as Infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), Energy dispersive X-ray spectroscopy (EDX), Vibrating sample magnetometry (VSM), Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), Thermo-gravimetric analysis (TGA) and NMR-detected hydrogen/deuterium (H/D) exchange technique. The synthesized nanocomposite was employed as a new base catalyst for the synthesis of some novel spirooxindole compounds and highly substituted dihydro-2-oxopyrroles in aqueous media with good to excellent yields. This heterogeneous base catalyst could be recycled and reused up to ten times without appreciable loss of activity. [Display omitted] [ABSTRACT FROM AUTHOR]

The present work demonstrates that the capability of Al3+ ions as a dopant in the mesoporous tin dioxide (SnO 2) nanopowders for humidity sensor and electrochemical applications. Al3+ ions substituted mesoporous SnO 2 were prepared by facile hydrothermal method. The influence of Al3+ ions concentration on structural, morphological, optical and electrochemical properties of mesoporous SnO 2 were studied in detail using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), High resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, Brunner-Emmett-Teller (BET), Ultra Violet-visible (UV vis.) absorption spectroscopy, Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) studies. The electrochemical results indicated that a good electrochemical performance and it can be used in energy storage devices. Besides, higher percentage of Al3+ ions enhanced on the humidity sensitivity at different temperatures and the material exhibit excellent characteristics as humidity sensor. The resistance value decreases with increase of Al3+ ions doping. The increase of humidity sensing response with the increase of Al3+ doping concentration, due to increase of surface area and porosity, which showed the sensing response time and recovery time around 87s and 64s, respectively, and it revealed that the sample has quick response and recovery time. The stability study confirms the Al3+ ions substituted SnO 2 (x = 0.05) sample showed good stability as a humidity sensor. • Al3+ substituted SnO 2 nanopowders were prepared by facile hydrothermal method. • Electrochemical studies indicated a good performance of materials for the use in energy storage devices. • Sn 1-x Al x O 2 (x = 0.05) showed enhanced electrochemical performance compared to other samples. • Humidity sensitivity measurement showed excellent characteristics as humidity sensor. [ABSTRACT FROM AUTHOR]

This work investigates the degradation of the azo dye solochrome dark blue (SDB) by measurement of the photocatalytic, sonocatalytic and sonophotocatalytic activities, under low ultrasonic frequency (40 kHz) and UV-C (254 nm) light, using Mn-doped ZnS semiconductor quantum dots (Mn2+:ZnS Qds) as catalysts, prepared by a simple chemical precipitation procedure. In order to study the different morphological and optical crystal properties, various characterization techniques were used, such as high resolution transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, N2 adsorption-desorption at −196 °C and ultraviolet-visible spectroscopy. The average particle size of the semiconductor Qds was in the range of 3–4 nm. The optimal parameters affecting dye degradation, such as the catalyst loading, solution pH, time of irradiation, initial concentration of dye, dopant concentration, ultrasonic power and frequency effect were evaluated. The synthesized catalytic material exhibited a high activity for sonophotocatalytic degradation of SDB (89%), larger than that observed for sonocatalysis (69.7%) or photocatalysis (55.2%) alone, which was due to the improved electron-holes separation, formation of more reactive radicals and enhancement of the active surface area. Qds showed good stability and reusability after five repeated cycles. Finally, the degradation products were identified by liquid chromatography-mass spectrometry (LC-MS). [ABSTRACT FROM AUTHOR]