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I–III–VI multinary semiconductors, which have low toxicity, are attracting much attention as quantum dot (QD) materials for replacing conventional binary semiconductors that contain highly toxic heavy metals, Cd and Pb. Recently, the inherent design flexibility of multinary QDs has also been attracting attention, and optoelectronic property control has been demonstrated in many ways. Besides size control, the electronic and optical properties of multinary QDs can be changed by tuning the chemical composition with various methods including alloying with other semiconductors and deviation from stoichiometry. Due to significant progress in synthetic methods, the quality of such multinary QDs has been improved to a level similar to that of Cd-based binary QDs. Specifically, increased photoluminescence quantum yield and recently narrowed linewidth have led to new application fields for multinary QDs. In this review, a historical overview of the solution-phase synthesis of I–III–VI QDs is provided and the development of strategies for better control of optoelectronic properties, i.e. , electronic structures, energy gap, optical absorption profiles, and photoluminescence feature, is discussed. In addition, applications of these QDs to luminescent devices and light energy conversion systems are described. The performance of prepared devices can be improved by controlling the optical properties and electronic structures of QDs by changing their size and composition. Clarification of the unique features of I–III–VI QDs in detail will be the base for further development of novel applications by utilizing the complexity of multinary QDs. [Display omitted] • Solution-phase synthesis of I–III–VI semiconductor quantum dots (QDs). • Controlling electronic energy structure of I–III–VI QDs by size and composition. • Improving photoluminescent properties of I–III–VI QDs with the control of their composition and nanostructure. • Applications based on unique optoelectronic properties of I–III–VI QDs. [ABSTRACT FROM AUTHOR]

Metal nanoparticle‐based electrocatalysts are widely used in electronic devices, which serve for electrochemical reactions like oxygen reduction reaction, alcohol oxidation and CO2 reduction reaction. These catalyst‐dependent reactions are the key of the emerging clean energy systems. Catalyst design and synthesis therefore have received keen attention in past decades. We are motivated to study synthesis approaches of metal nanoparticle‐based electrocatalysts using ionic liquids (ILs), which are promising solvents for the nanoparticle preparation because of their unique physicochemical properties. In this personal account, we review our previous and present works on nanoparticle preparation in IL and utilization of the obtained nanoparticles as electrocatalysts. [ABSTRACT FROM AUTHOR]

Photosensitization of semiconductors by excitation of chiral plasmonic metallic nanostructures has attracted much attention, not only for the analysis and detection of circularly polarized light but also for its potential applications in chiral photosynthesis. Although there have been reports on the detection of semiconductor-sensitized current in chiral nanostructures precisely fabricated by physical vapor deposition and/or lithography techniques, there have been no studies using plasmonic metal nanocolloids synthesized by chemical processes. In this study, we report the establishment of a fabrication method for large-area chiral photoelectrodes and the semiconductor photosensitization phenomenon realized using chiral plasmonic nanoparticles. Chiral plasmonic Au nanoparticles prepared by previously reported colloidal methods were immobilized onto a TiO2 thin film electrode by electrophoresis. When TiO2 electrodes loaded with chiral Au nanoparticles synthesized using L-cysteine were irradiated with circularly polarized light, left circularly polarized light irradiation at a wavelength of 500–600 nm generated a larger anodic photocurrent than right circularly polarized light irradiation at the same wavelength. This trend was reversed for TiO2 electrodes immobilized with colloidal Au nanoparticles synthesized with D-cysteine. From these results, we conclude that the efficiency of photocurrent generation by chiral plasmon excitation can be controlled by the polarization direction of the incident light. [ABSTRACT FROM AUTHOR]

Abstract: Luminescent semiconductor nanoparticles have been applied to temperature measurements, because their emission is intense and the emission wavelength can be adjusted by particle size. However, most of luminescent nanoparticles contain highly toxic elements such as Cd, Se, and Te. In this study, the temperature characteristics of a new low-toxic luminescent nanoparticles, ZnS–AgInS2 (ZAIS), have been investigated. The temperature sensitivity of luminescent intensity of ca. −1%/K was comparable to other luminescent nanoparticles. The thermally induced red shift of ca. 0.1nm/K was observed, which is similar to other nanoparticles. The measurement revealed that the oxygen sensitivity of ZAIS is negligibly small. It is also shown that ZAIS nanoparticles are photostable compared with CdSe/ZnS. As a result, ZAIS is one of the most preferable candidates to take the place of other toxic nanoparticles especially for bio-related experiments. [Copyright &y& Elsevier]

Abstract: Structural and energetic investigations based on semiempirical PM5 and ab initio HF and MP2 calculations suggested that the self-assembled monolayer of an atropisomeric compound, (R)- or (S)-1,1′-binaphthalene-2,2′-dithiol (BNSH), on a gold (111) surface selectively adsorbs one enantiomer of phenylalanine (Phe), resulting in chiral discrimination, through hydrophobic, cation(−–π and NH(Phe)–π (BNSH) interactions in a nanometer-sized screw-hole-like pocket composed of three BNSH molecules in the monolayer. [Copyright &y& Elsevier]

Gold (Au) nanoparticles were deposited inside silica: (SiO2) shells containing cadmium sulfide (CdS) nanoparticles through photocatalytic reduction of potassium dicyanogold(I) by CdS. Photocatalytic Au deposition occurred only when core-shell nanoparticles having a void space between the core and shell, i.e., a jingle-bell-shaped structure, were used. These core-shell nanoparticles were prepared by size-selective photoetching of SiO2 -covered CdS nanoparticles. The size of Au nanoparticles could be controlled by adjustment of the void space in SiO2-covered CdS. Dissolution of CdS by acid treatment from the Au-deposited jingle-bell nanoparticles did not have any effect on the surface-plasmon absorption by Au. These facts indicate that Au nanoparticles of adjustable size can be prepared in an SiO2 shell that prevents mutual coalescence of Au nanoparticles but allows permeation of molecules and ions. [ABSTRACT FROM AUTHOR]

Photocatalytic deposition of gold (Au) and silver (Ag) nanoparticles was investigated using jingle-bell-shaped silica (SiO2)-coated cadmium sulfide (CdS) nanoparticles (SiO2/CdS), which each had a void space between the CdS core and SiO2 shell, as a photocatalyst. A size-selective photoetching technique was used to prepare the jingle bell nanostructure of SiO2/CdS. Nanoparticles of Au and Ag were deposited by irradiation of the photoetched SiO2/CdS in the presence of the corresponding metal complexes under deaerated conditions. Chemical etching of Au-deposited particles enabled the selective removal of CdS without any influence on the surface-plasmon absorption of Au. TEM analyses of the resulting particles suggested that some particles were encapsulated in hollow SiO2 particles, while other Au particles were deposited on the outer surface of the SiO2 shell. Emission spectra of the photoetched SiO2/CdS showed that the metal deposition developed a broad emission with a peak around 650 nm originating from surface defect sites, the degree being dependent on the kind of metal nanoparticles and their amount of deposition. This fact can be explained by the formation of metal–CdS binary nanoparticles having defect sites at the interface between metal and CdS. [ABSTRACT FROM AUTHOR]

Light intensity dependence of action spectra of photocatalytic reactions was investigated using anatase single-phase titanium(IV) oxide powders as photocatalysts. The action spectra normalized at 350 nm were not changed in methanol dehydrogenation with the range of intensities of ca. 0.1–10 mW cm-2, while those for acetic acid decomposition were red-shifted with increase in light intensity. The apparent quantum yield of the former was almost independent of the irradiation intensity, but that of the latter was declined with increase in light intensity, the degree being considerably enhanced with the irradiation at shorter wavelength when the light intensity was higher than 2 mW cm-2. These can be explained by the difference in the utilization efficiency of photogenerated charge carriers. [Copyright &y& Elsevier]

Layer-by-layer accumulation of monolayers of silica-coated cadmium sulfide (CdS) was achieved through repeated monolayer deposition–hydrolysis cycles using CdS particles (average diameter: 5 nm) modified with 3-mercaptopropyltrimethoxysilane (MPTS) and glass substrates. Absorption spectroscopic analyses of the resulting yellow films revealed that each layer had almost the same thickness, the estimated density of which corresponded to ca. 66% of that for close hexagonal packing of nanoparticles. Monochromatic light irradiation at 488, 458, or 436 nm onto the film immersed in oxygen-saturated aqueous methylviologen solution caused a decrease in the size of the CdS core depending on the irradiation wavelength, while atomic force microscopic analyses suggested that the size of the silica shell of the immobilized nanoparticles was almost unchanged by irradiation, i.e., the immobilized silica-coated CdS nanoparticles had void spaces between the photoetched core and the silica shell, and their sizes could be regulated by choosing the wavelength of irradiation light. This size-selective photoetching was applied to nanoparticulate films that had been heat-treated at 473, 573 or 673 K to observe the blue-shift of the absorption edge of CdS to the irradiation wavelength. The amount of CdS remaining in the film after the photoetching process depended on the temperature of heat treatment. The largest amount among as-prepared and heat-treated samples was obtained at 473 K and decreased with an increase in temperature. The growth of particles, i.e., the diminution of particle number, and/or the diminution of number of separated independent shells may account for this dependence. [Copyright &y& Elsevier]

PbS ultrathin films were prepared by sequential underpotential deposition of S and Pb on Au(111) substrates. Observations of the resulting films with high resolution electron microscopy and energy dispersive X-ray spectrometry revealed the deposition of PbS thin films having the cubic rock salt crystal structure, the (200) planes of which were parallel to the Au surface. The scanning tunneling microscope images showed that the surface of the prepared PbS film was flat on an atomic level and no large protrusions were present, while etch pits with the height of the monatomic step of Au(111) were seen through the deposited films irrespective of the number of PbS monolayers. The PbS film-deposited Au electrodes showed anodic photocurrents in an aqueous solution containing triethanolamine as a sacrificial electron donor. The onset wavelength of their action spectra was largely blue-shifted from that of the bulk PbS due to the size quantization effects. The energy gap of the PbS thin films determined from the action spectra of anodic photocurrents decreased with an increase in the film thickness. [Copyright &y& Elsevier]

Quantum dots (QDs) are important luminescent structures with applications in wide‐color‐gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs are expected to serve as eco‐friendly materials to replace conventional QDs owing to the narrow spectral widths and tunable bandgaps of these QDs. However, the application of multinary QDs, which tend to exhibit defect‐related emissions, to QD light‐emitting diode (QLED) displays will require electroluminescence to be obtained from QLEDs incorporating inkjet‐printed emitting layers. The present work examines QLEDs exhibiting vibrant color emissions based on blue‐emitting Zn–Se–Te QDs, green‐emitting Ag–In–Ga–S QDs, and red‐emitting Ag–Cu–In–Ga–S QDs. Each such QLED contains QD emitting layers comprising a mixture of charge transport materials. The spectra obtained from these RGB QLEDs fabricated by spin‐coating show very high color purity. Passive matrix QLED displays incorporating these QDs are also fabricated by inkjet printing to demonstrate the high color purity that can be obtained from multinary QDs in displays. In conjunction with passive matrix driving, these displays produce clear moving images with vibrant electroluminescence originating from the multinary QDs. The present results indicate that these QDs have significant potential for utilization in wide‐color‐gamut displays. [ABSTRACT FROM AUTHOR]

Presents a study of the effects of adsorbents for titanium dioxide on photocatalytic degradation of propyzamide. Factors reducing the concentration of solution-phase intermediates; Rate of propyzamide mineralization; Mineralization of organic pollutants; Photodecomposition reaction of propyzamide; Reaction modes of photoinduced mineralization of propyzamide on photocatalysts.

Discusses the structure of the capped semiconductor surfaces in atomic scale. Preparation and characterization of PbS microcrystals; Stability to agglomeration; Photoreduction of methyl violegen; Effect of structure on photoelectrochemical and photochemical properties.

Sputter deposition of gold (Au) onto ionic liquids (ILs) resulted in the formation of highly dispersed Au nanoparticles without additional chemical species, such as reducing and/or stabilizing agents. The Au nanoparticles in 1-ethyl-3-methylimidazolium tetrafluoroborate had an average diameter (dav) of 5.5 nm with a standard deviation (σ) of 0.86 nm, while sputter deposition onto N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide resulted in the formation of much smaller Au nanoparticles with dav of 1.9 nm and σ of 0.46 nm. Prolongation of sputtering time results in a higher concentration of Au nanoparticles in ILs, but did not cause a remarkable change in their size. [ABSTRACT FROM AUTHOR]

Silver indium sulfide/gallium sulfide (AgInS2/GaSx) core/shell quantum dots (QDs), among the cadmium-free alternatives that possess a narrow band-edge emission, have attracted immense attention in recent years. However, the insufficient stability of photoluminescence (PL) due to chemically sensitive GaSx shells, which is partly caused by easy desorption of passivated ligands, remained a problem for their practical application. In this study, a simple and efficient method to protect these QDs is presented. The AgInS2/GaSx core/shell QDs are encapsulated into metal–organic frameworks (MOFs) consisting of an indium-fumarate ordered structure (InMOFs). Whereas damage to the shell during the encapsulation reaction can potentially occur, the obtained composite (AgInS2/GaSx@InMOFs) maintains a narrow band-edge emission that is mostly identical to the pristine AgInS2/GaSx core/shell QDs with a PL quantum yield (PL QY) of 12.6% after optimization of the synthesis-solution pH. The encapsulation result enables the spectral shape and PL QY of the composite to be maintained after 7 days, which demonstrates the high stability of the QDs encapsulated in InMOFs. [ABSTRACT FROM AUTHOR]

Narrowing the emission peak width and adjusting the peak position play a key role in the chromaticity and color accuracy of display devices with the use of quantum dot light-emitting diodes (QD-LEDs). In this study, we developed multinary Cu–In–Ga–S (CIGS) QDs showing a narrow photoluminescence (PL) peak by controlling the Cu fraction, i.e., Cu/(In+Ga), and the ratio of In to Ga composing the QDs. The energy gap of CIGS QDs was enlarged from 1.74 to 2.77 eV with a decrease in the In/(In+Ga) ratio from 1.0 to 0. The PL intensity was remarkably dependent on the Cu fraction, and the PL peak width was dependent on the In/(In+Ga) ratio. The sharpest PL peak at 668 nm with a full width at half maximum (fwhm) of 0.23 eV was obtained for CIGS QDs prepared with ratios of Cu/(In+Ga) = 0.3 and In/(In+Ga) = 0.7, being much narrower than those previously reported with CIGS QDs, fwhm of >0.4 eV. The PL quantum yield of CIGS QDs, 8.3%, was increased to 27% and 46% without a PL peak broadening by surface coating with GaSx and Ga–Zn–S shells, respectively. Considering a large Stokes shift of >0.5 eV and the predominant PL decay component of ∼200–400 ns, the narrow PL peak was assignable to the emission from intragap states. QD-LEDs fabricated with CIGS QDs surface-coated with GaSx shells showed a red color with a narrow emission peak at 688 nm with a fwhm of 0.24 eV. [ABSTRACT FROM AUTHOR]

Phthalocyanine ruthenium complexes were identified as red-light activatable catalysts for trifluoromethylation reactions. The red-light mediated chlorotrifluoromethylation of alkenes could proceed without any sacrificial reducing reagents. This reaction exhibited good compatibility with a blue-light-absorbing substrate, while under irradiation with blue light, i.e., under traditional photoreaction conditions, this substrate decomposed completely. [ABSTRACT FROM AUTHOR]

Robust surface protective materials for practical applications of luminescent semiconductor quantum dots (QDs) that differ from conventional organic ligands are required for long-term QD stability. Among the alternatives, metal–organic frameworks (MOFs) are expected to act as functional stabilizers because of their insulating or semiconducting properties and the versatility of material design. Here, a new strategy for developing a QD@MOF composite is proposed without any bonding materials between the QD and MOF-like polymers. Forming a direct bond between QDs and MOFs is desirable for exploiting the synergistic effects of both materials. The dropwise addition of MOF precursors into QD solutions, ligands of which have been exchanged to easily detach pyridine derivatives, demonstrates the growth of MOFs on the direct surface of QDs. How these QDs are incorporated in MOFs is investigated in relation to the manner of MOF precursor introduction during the synthesis reaction. The resulting QD@MOF composite emits intense photoluminescence in the solid state, and complete coverage of the MOF on the QD surface was demonstrated by the unresponsiveness of the composite to photoluminescence quenching tests. [ABSTRACT FROM AUTHOR]

The article discusses a study on a novel strategy to synthesize nanoparticles of ZnS-AgInS2 solid solution for a color-adjustable luminophore. Solid solution nanoparticles are prepared by thermal decomposition of a metal ion-diethyldithiocarbamate complex. It is concluded that highly luminiscent ZnS-AgInS2 solid solution nanoparticles containing non-highly toxic elements have been successfully prepared.

Discusses the advantage of the size-selective photoetching technique for precise modification of core size after preparation of cadmium sulfide (CdS) core and silica shell structures. Diffuse reflectance spectra of silica-coated CdS nanoparticles; CdS nanoparticles in inverse micelles.

We prepared a solid-state Z-scheme photocatalyst in which zinc rhodium oxide (ZnRh2O4) and bismuth vanadium oxide (Bi4V2O11) that served as hydrogen (H2) and oxygen (O2) evolution photocatalysts, respectively, were connected with gold (Au) nanoparticles. The Au nanoparticles were prepared by sputtering in an ionic liquid, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, to generate Au/ZnRh2O4/Au/Bi4V2O11 with various amounts of Au in the 12 mol. %–29 mol. % range (vs 1.0 mol ZnRh2O4 + 0.2 mol Bi4V2O11). Au/ZnRh2O4/Au/Bi4V2O11 photocatalyzed overall pure-water splitting under irradiation with red light at a wavelength of 700 nm, and the dependence of the amounts of Au on the apparent quantum efficiency tended to increase in the measurement range. [ABSTRACT FROM AUTHOR]

Abstract: Pt nanoparticles can be produced by a Pt sputtering method onto trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide (Me3PrNTf2N) room-temperature ionic liquid (RTIL) without stabilizing agents. Pt nanoparticles obtained by the Pt sputtering method showed mean particle size of ca. 2.3–2.4nm independently of sputtering time. A Pt-embedded glassy carbon electrode (Pt-GCE) consisting of the Pt-sputtered RTIL and a glassy carbon plate showed a favorable catalytic activity to oxygen reduction reaction. The catalytic ability was enhanced by Me3PrNTf2N modification of the Pt-GCE. In addition, carbon monoxide never absorbed onto the RTIL-modified Pt-GCE. [Copyright &y& Elsevier]

Abstract: Based on our previous finding that room temperature ionic liquid (RTIL) can be observed by scanning electron microscopy (SEM) without charging of the liquid, a specifically designed electrochemical cell has been developed to observe electrochemical metal deposition from RTIL in real time by SEM. The cell was fabricated employing a fluorine doped tin oxide transparent glass, whose surface was divided into three electrodes. Then, the effectiveness of the fabricated cell was confirmed by demonstrating silver deposition form RTIL of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI-TFSI) containing Ag-TFSI, which gave growth of granular and dendritic forms of Ag deposit. [Copyright &y& Elsevier]

Abstract: Photoabsorption properties of titanium(IV) oxide powders were investigated by photoacoustic (PA) spectroscopy. The photoacoustic spectra obtained under steady-state ultraviolet irradiation showed appearance and growth of two kinds of PA signal bands, which were attributable to trivalent titanium species (Ti3+) and trapped holes or surface peroxide species. The saturation limit of the PA signal was estimated by analyzing the time course of Ti3+ signals and compared to the density of Ti3+ determined by a photochemical method. The results suggest that the photoacoustic spectroscopic technique is a feasible alternative method for estimation of Ti3+ as an empirical measure of defect density. [Copyright &y& Elsevier]

A novel photocatalytic reaction system, composed of solution and gas spaces that are divided by a thin Teflon film and titanium(IV) oxide (TiO2)-coated mesh or cloth, for the treatment of contaminated aqueous solutions was developed to be operated with enhanced aeration without bubbling of air in the solution. First, the photocatalytic activities of TiO2 particles immobilized on two kinds of support material, stainless steel mesh (SSM) and fiberglass cloth (FGC), were investigated for photocatalytic oxidation of 2-propanol, as a model volatile organic compound, dissolved in aerated aqueous solution. The TiO2 particles immobilized on both support materials exhibited photocatalytic activity to oxidize 2-propanol into acetone and carbon dioxide (CO2), and the activity levels of the TiO2 particles immobilized on the two kinds of support materials were comparable. Presumably due to the presence of a small amount of metal species originating in SSM that might work as reduction catalysts, molecular hydrogen (H2) was also liberated on the TiO2-immobilized SSM. Results of analysis of weight loss after photoirradiation suggested that the stability of the TiO2-immobilized FGC was better than that of the TiO2-immobilized SSM. On the basis of these results, FGC was employed in construction of a photocatalytic reactor equipped with an oxygen (O2)-permeable Teflon membrane in order to make oxygen pass from a gas space to a solution space and to keep the surface of the immobilized TiO2 photocatalyst, facing an aqueous solution containing volatile organic compounds, saturated with dissolved O2. From the results of photocatalytic oxidative decomposition of 2-propanol, it was clarified that the surfaces of TiO2 particles could be sufficiently supplied with O2 from the gas space through the membrane to accelerate the oxidation. [Copyright &y& Elsevier]

Surface modification of titanium(IV) oxide (TiO2) powders with 1,1′-binaphthalene-2,2′-diol (bn(OH)2), having two phenolic hydroxyls and atropisomeric chirality, in refluxed ethanol led to the formation of a deep yellow-colored surface complex, giving visible-light absorption at a wavelength below ca. 550–600 nm. Quantitative analyses of the surface complex revealed that absorption intensity at 450 nm in diffuse reflection (DR) measurement was almost proportional to its amount and that its amount depended strongly on the amount of surface hydroxyl groups of TiO2 but not on the crystal structure of TiO2, anatase, and rutile. The bn(OH)2 complexation was also applied to platinized TiO2 to drive photocatalytic molecular hydrogen (H2) evolution from deaerated triethanolamine solutions under visible-light irradiation at a wavelength even longer than 540 nm. The photonic efficiency of the photocatalytic reaction at 450 nm was estimated to be 0.02% for bn(OH)2-modified TiO2 (JRC-TIO-3) loaded with 0.1 wt.% of platinum. On the basis of these experimental results, the reaction mechanism, which involves visible-light excitation of the surface complex, injection of electrons from the complex to TiO2, and migration of the electrons to platinum deposits, where reduction of H+ takes place to give H2, was elucidated. [Copyright &y& Elsevier]

We report a new Förster resonance energy transfer (FRET) system for structural analyses of DNA duplexes using perylene and Cy3 as donor and acceptor, respectively, linked at the termini of a DNA duplex via D‐threoninol. Experimentally obtained FRET efficiencies were in good agreement with theoretical values calculated based on canonical B‐form DNA. Due to the relatively long Förster radius, this system can be used to analyze large DNA structures, and duplexes containing photo‐reactive molecules can be analyzed since perylene can be excited with visible light. The system was used to analyze a DNA duplex containing stilbene, demonstrating that in the region of the stilbene cluster the duplex adopts a ladder‐like structure rather than helical one. Upon photodimerization between stilbene residues, FRET efficiencies indicated the reaction does not disturb DNA duplex. This FRET system will be useful for analysis of photoreactions of nucleobases as well as a wide range of nucleic acid structures. [ABSTRACT FROM AUTHOR]

Redox-dependent emission quenching of low toxic ZnS-AgInS2 semiconductor nanocrystals was studied and the obtained behavior was found to be applicable to fabrication of fluorescent biosensors in combination with redox enzymes. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are expected to be used as an emitting material in wide-color-gamut displays. However, the development of low-toxicity alternatives is necessary because QDs that exhibit high color purity and highly efficient emission contain toxic materials such as Cd. Here, QD light-emitting diodes (QD-LEDs) fabricated using AgInS2/GaSx core/shell QDs (AIS core/shell QDs) as low-toxicity QDs were investigated. The photoluminescence (PL) spectrum of an AIS core/shell QD dispersion showed a band edge emission with a peak wavelength of 560 nm and a full-width at half-maximum of 45 nm because the GaSx shell suppressed the surface defects. Electroluminescence (EL) emission, which mainly comprises the band edge emission, was realized in the AIS-based QD-LED. However, the EL spectra included a large defect emission component, together with the band edge emission. The defect emission was attributed to electrons flowing in the emitting layer (EML) being easily trapped at defect levels in the QDs. The addition of tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB) as an electron transporting material to the EML effectively suppressed the defect emission. The radiation-energy ratio of the band edge emission to the total emission was 50% in the QD-LED without 3TPYMB and was improved to 64% in the QD-LED with 3TPYMB; this ratio was comparable to that in the PL spectrum of the AIS core/shell QD film. The addition of 3TPYMB improved electron injection into the QDs and the carrier balance in the EML. As a result, the defect emission was suppressed and the EL characteristics were improved. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots (QDs), which exhibit highly saturated color emission, are expected to be used as emitting materials in wide-color-gamut displays. However, the development of low-toxicity alternatives is necessary because QDs with high color purity and highly efficient emission contain toxic materials such as Cd and Pb. In this study, QD light-emitting diodes (QD-LEDs) with ZnS–AgInS2 solid-solution nanoparticles [(AgIn)xZn2(1−x)S2, ZAIS] as low-toxicity QDs were fabricated and their electroluminescence properties were investigated. The ZAIS QDs exhibited red photoluminescence, with a peak wavelength of ca. 700 nm. Because the charge-injection barrier of ZAIS QDs without a wide-bandgap shell is relatively low, the QD-LEDs with red ZAIS QDs in combination with organic charge-transport materials induce electron injection from an organic electron-transport layer. These QD-LEDs exhibit an external quantum efficiency of 2.2%, a turn-on voltage of 2.4 V, and red emission with chromaticity coordinates (0.66, 0.33). [ABSTRACT FROM AUTHOR]

Highlights • Nontoxic nanoparticles of water-soluble ZAIS@ZnS-MPA was prepared for bio-imaging. • PL characteristics of novel ZAIS nanoparticles were studied on the plasmonic chip. • Enhanced PL of ZAIS was observed with the plasmonic chip in wide wavelength range. • PL of ZAIS shows the photobleaching resistance to apply for long-time observation. Abstract Quantum dots (QDs) are semiconductor nanoparticles showing many advantages for photoluminescence (PL) applications. Since common QDs contain toxic elements such as Cd, Pb, Se, and Te, ZnS-AgInS 2 (ZAIS) has been developed as a quantum nanomaterial with low cytotoxicity. In this study, ZAIS@ZnS core-shell QDs coated with carboxyl groups (ZAIS@ZnS-MPA) were prepared as water-soluble nanoparticles. The PL characteristics of ZAIS@ZnS-MPA were studied on a plasmonic chip, which is a substrate with wavelength-scale periodic structures coated with thin metal films, and the PL enhancement of ZAIS by an electromagnetic field derived from grating-coupled surface plasmon resonance (GC-SPR) was also evaluated. The PL spectroscopic characteristics obtained on the grating patterns with a 480 nm-pitch were enhanced in a wider wavelength range. Furthermore, photobleaching, which occurs in conventional fluorescence molecules, was not observed under halogen lamp illumination. The PL and spectroscopic imaging under a microscope indicated the PL characteristics of the ZAIS@ZnS-MPA nanoparticles on the plasmonic chip under appropriate conditions. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) stability of ZnS-AgInS 2 (ZAIS) nanoparticles (NPs) prepared via thermal decomposition of (AgIn) x Zn 2(1-x) (S 2 CN(C 2 H 5 ) 2 ) 4 (x = 0.5, 0.8 and 1.0) was improved by ionic liquids (ILs) of 1-ethyl-3-metylimidazolium ethylsulfate (EMI-es) and tris (2-hydroxyethyl) methylammonium methylsulfate (HEMA-mes). Through ligand exchange processes from oleylamine (OLA) to sodium 2-mercaptoethanesulfonic acid (MES), hydrophilic NP’s surfaces changed into hydrophobic ones, resulting in that the ZAIS NPs could be dispersed in the ILs. UV irradiation caused the PL deterioration of ZAIS NPs in solutions, but MES-ZAIS NPs in the ILs exhibited higher PL stability than the OLA-ZAIS NPs in chloroform, the degree being more remarkable for NPs dispersed in HEMA-mes than in EMI-es. The improvement of PL stability could be interpreted as a result of stabilization of MES adsorbed on the NPs through electrostatic interaction between MES and the ILs. Exposing to the air and mixing with the water accelerated the PL deterioration of the NPs. [ABSTRACT FROM AUTHOR]

Oxidation of molten In–Sn alloys was carried out in ionic liquids by heat treatment with vigorous stirring, resulting in the formation of indium tin oxide (ITO) nanocrystals. The ITO nanocrystals exhibited a plasmon peak, the peak wavelength of which was blue-shifted with an increase in the Sn fraction in ITO. [ABSTRACT FROM AUTHOR]

An effective preparation method of Au nanoparticles (NPs) is presented, wherein an arc plasma deposition technique is combined with ionic liquids (ILs) used as capture media. This method requires no chemical reaction. By selecting ILs, size-controlled Au NPs are produced easily and on a massive scale. [ABSTRACT FROM AUTHOR]

Sputter deposition onto ionic liquids (ILs) was applied to synthesize AuCu bimetallic alloy nanoparticles (NPs) dispersed in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4). A mixed target of Au and Cu materials was used for simultaneous sputter deposition onto the IL under an Ar pressure of 10 Pa. Two types of heating procedures within the range of 323–573 K were examined for control of the structures of NPs, particularly addressing the phase transition of the alloy NPs from the face centered cubic (fcc) structure to the L10 structure. One was heating after the sputter deposition in N2 at atmospheric pressure for 1 h. Another was a combination of heating during the sputter deposition and subsequent heating under an Ar pressure from 0.5 to 0.8 Pa for 1 h. Although both cases exhibited lowering of the phase transition temperatures compared with the temperature for the bulk, the latter procedure at 423 K only provided the NPs (approx. 5 nm) consisting of the L10 structure in the dispersed manner. A mechanism for forming the L10 structure was proposed for explaining the difference between results obtained using the two procedures. [ABSTRACT FROM AUTHOR]

Near‐IR‐responsive semiconductor nanocrystals (NCs) of Ag8SnS6 composed of low‐toxic elements are newly developed by the thermal decomposition of precursors in oleylamine. The size of Ag8SnS6 NCs can be controlled from 6 to 13 nm by increasing reaction temperature. The photosensitization of ZnO rod electrodes with Ag8SnS6 NCs is much more efficient than those with conventional Ag‐based NCs such as Ag2S. [ABSTRACT FROM AUTHOR]

Abstract: Multilayer films composed of Au particle/titania nanosheet (TNS)/CdTe nanoparticle were successfully prepared using a layer-by-layer-deposition technique. CdTe nanoparticles were accumulated as the topmost layer on TNS/poly(diallyldimethylammonium) (PDDA) bilayers deposited on the substrates of an Au particle film or an F-doped SnO2 (FTO) electrode. CdTe nanoparticles were acted as a photosensitizer. The photogenerated electrons in CdTe nanoparticles were injected into the conduction band of titania nanosheets to produce anodic photocurrent at a more positive potential than −0.4V vs. Ag/AgCl. The magnitude of photocurrent was much larger for the films prepared on the Au particle film rather than that on the FTO electrode. Furthermore, with an increase in the thickness of (TNS/PDDA) bilayers, that is, the distance between Au and CdTe nanoparticles, the photocurrent was drastically decreased. The enhancement factor of photocurrent, defined as the ratio of the magnitude of photocurrent obtained with CdTe particle layer immobilized on Au layer to that on FTO, was varied from 2 to 10 by changing the wavelength of irradiation light. The broad peak at 520nm appeared in the action spectrum of the enhancement factor and its profile roughly corresponded to the localized surface plasmon resonance peak of Au particle layer whose peak wavelength was ca. 540nm. These facts indicated that the photoexcitation of the surface plasmon of Au particles, which produced a locally enhanced electric field near Au particle layer, played an important role in the increase in the photoexcitation probability of CdTe nanoparticles deposited as the topmost layer. [Copyright &y& Elsevier]

Abstract: Modification of the excimer emission of N,N′-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylene dicarboximide (PDI) by localized surface plasmon resonance (LSPR) of silver nanocubes (SNCs) 100–170nm in size was investigated by single-particle spectroscopy. SNCs were immobilized on a glass substrate and then covered with a 20-nm-thick PDI film via vacuum vapor deposition. Using fluorescence microscopy to compare areas with and without single SNCs on the same sample, we demonstrated the enhanced intensity and modulated spectral shape of the excimer emission by single SNCs. The excimer emission modification was examined for various sizes of SNCs and different LSPR peak positions, and the electromagnetic field enhancement effect on the radiation emission process was discussed. [Copyright &y& Elsevier]

Abstract: UV-light induced redox reactions between cationic porphyrins (H2TMPyP) and methyl viologen (MV2+) separately incorporated in titania nanosheets (TNS) and cubic-mesoporous silica (MPS) integrated films, respectively, were investigated. In this system, the following two modified hybrids, i.e., the normally stacked (MV2+–TNS)/(H2TMPyP–MPS) on a FTO electrode and the inversely stacked (H2TMPyP–MPS)/(TNS) films on a FTO electrode were examined. In accordance with the expected electron flow from H2TMPyP to MV2+, cathodic photocurrents were observed for the normally stacked film in acetonitrile (CH3CN) under a negative bias voltage of −0.4V. However, under the influence of a positive bias voltage of +0.3V, anodic photocurrents were observed even in CH3CN. On the other hand, anodic photocurrents were also observed in water for the normally stacked films at both bias voltages of +0.3 and −0.4V due to photoreduction followed by proton abstraction of the H2TMPyP molecules from H2O within the MPS nano-cavities. In addition, ca. 0.98 mC of the photocurrents were determined in water for the inversely stacked (H2TMPyP–MPS)/(TNS) films without MV2+, of which ca. 50% resulted in the oxidative consumption of H2TMPyP in the MPS cavities. [Copyright &y& Elsevier]

Abstract: Based on our previous discovery that ionic liquid (IL) can be observed by a scanning electron microscope (SEM) without charging the liquid, we have developed several novel techniques for SEM observation. Coating of insulating sample with IL is useful for providing electronic conductivity to the samples like metal or carbon coating by vacuum vapor deposition. In this case, dilution of the IL with appropriate volatile solvent like alcohol is effective for coating thin layer of IL on the sample. As a biological sample, seaweed including IL was attempted to be observed by SEM. A seaweed leaf swollen by water was put in an IL bath and the bath was put in an outgassed desiccator to replace water in the seaweed leaf with IL. The resulting sample gave a SEM image of the swollen seaweed whose thickness was several times larger than dried one. Furthermore, the introduction of the IL in vacuum chamber allowed us to develop the in situ electrochemical SEM observation system. Using this system, we observed changes in polypyrrole film thickness caused by the redox reaction of the film and the electrochemical deposition of silver and its oxidative dissolution. It was also found that the energy dispersive X-ray fluorescence (EDX) analysis was available even for the electrode polarized in IL. [Copyright &y& Elsevier]

Abstract: A nonionic surfactant, n-dodecyl glyceryl itaconate (DGI), self-assembles into bilayer membranes in water having a spacing distance of sub-micrometer in the presence of small amounts of ionic surfactants, and shows beautiful iridescent color. Ionic surfactants have strong effects on this iridescent system. We have interestingly found that the iridescent color changes with time after mixing DGI and ionic surfactants and the color in equilibrium state changes greatly with concentration of the ionic surfactants. The time-dependent color change results from the transformation of DGI aggregate structure after being mixed with ionic surfactant. It is first found that the iridescent color of this nonionic system can be changed from red to deep blue by altering the concentration of ionic surfactants added even though the total concentration of surfactant is almost constant. Such large blue shift of the iridescent color in equilibrium state cannot be fully explained by the ordinary undulation theory applied so far for this phenomenon. The flat lamellar sheets tend to curve by increasing the concentration of ionic surfactants to form separated onion-like and/or myelin-like structures. These separated structures of lamellar system result in the decrease of spacing distance between bilayer membranes because some vacant spaces necessarily appear among these structures. [Copyright &y& Elsevier]

Abstract: Light-emission intensity of CdS nanoparticles doped in a PMMA film is enhanced by a UV irradiation in air, but the emission intensity is strongly de-enhanced at a low pressure of 10−5 torr. Atmospheric gas as well as UV irradiation is essential for the enhancement, and these enhancement and de-enhancement processes are almost completely reversible. The emission of CdS nanoparticles doped in a PMMA film is also quenched by applying an external electric field, suggesting that the non-radiative decay rate from the emissive exciton state is accelerated by an external electric field. To cite this article: Y. Ohara et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Highly luminescent silver indium sulfide (AgInS2) nanoparticles were synthesized by dropwise injection of a sulfur precursor solution into a cationic metal precursor solution. The two-step reaction including the formation of silver sulfide (Ag2S) nanoparticles as an intermediate and their conversion to AgInS2 nanoparticles, occurred during the dropwise injection. The crystal structure of the AgInS2 nanoparticles differed according to the temperature of the metal precursor solution. Specifically, the tetragonal crystal phase was obtained at 140 °C, and the orthorhombic crystal phase was obtained at 180 °C. Furthermore, when the AgInS2 nanoparticles were coated with a gallium sulfide (GaSx) shell, the nanoparticles with both crystal phases emitted a spectrally narrow luminescence, which originated from the band-edge transition of AgInS2. Tetragonal AgInS2 exhibited narrower band-edge emission (full width at half maximum, FWHM = 32.2 nm) and higher photoluminescence (PL) quantum yield (QY) (49.2%) than those of the orthorhombic AgInS2 nanoparticles (FWHM = 37.8 nm, QY = 33.3%). Additional surface passivation by alkylphosphine resulted in higher PL QY (72.3%) with a narrow spectral shape. [ABSTRACT FROM AUTHOR]

The facile synthesis of ZnS-AgInS2 (ZAIS) as cadmium-free QDs and their application, mainly in solar cells, has been reported by our groups. In the present study, we investigated the safety and the usefulness for labeling and in vivo imaging of a newly synthesized aqueous ZnS-coated ZAIS (ZnS-ZAIS) carboxylated nanoparticles (ZZC) to stem cells. ZZC shows the strong fluorescence in aqueous solutions such as PBS and cell culture medium, and a complex of ZZC and octa-arginine (R8) peptides (R8-ZZC) can achieve the highly efficient labeling of adipose tissue-derived stem cells (ASCs). The cytotoxicity of R8-ZZC to ASCs was found to be extremely low in comparison to that of CdSe-based QDs, and R8-ZZC was confirmed to have no influence on the proliferation rate or the differentiation ability of ASCs. Moreover, R8-ZZC was not found to induce the production of major inflammatory cytokines (TNF-α, IFN-γ, IL-12p70, IL-6 and MCP-1) in ASCs. Transplanted R8-ZZC-labeled ASCs could be quantitatively detected in the lungs and liver mainly using an in vivo imaging system. In addition, high-speed multiphoton confocal laser microscopy revealed the presence of aggregates of transplanted ASCs at many sites in the lungs, whereas individual ASCs were found to have accumulated in the liver. [ABSTRACT FROM AUTHOR]