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Owing to their excellent electrical conductivity and robust mechanical properties, carbon-based nanocomposites are being used in a wide range of applications and devices, such as electromagnetic wave interference shielding, electronic devices, and fuel cells. While several approaches have been developed for synthesizing carbon nanotubes and carbon-black-based polymer nanocomposites, most studies have focused on the simple blending of the carbon material with a polymer matrix. However, this results in uncontrolled interactions between the carbon filler and the polymer chains, leading to the agglomeration of the carbon filler. Herein, we report a new strategy for synthesizing sulfonated polystyrene (PSS)-grafted carbon black nanoparticles (NPs) via surface-initiated atom-transfer radical polymerization. Treatments with O2 plasma and H2O2 result in the effective attachment of the appropriate initiator to the carbon black NPs, thus allowing for the controlled formation of the PSS brushes. The high polymeric processability and desirable mechanical properties of the PSS-grafted carbon black NPs enable them suitable for use in nonfluorinated-hydrocarbon-based polymer electrolyte membranes for fuel cells, which must exhibit high proton conductivity without interrupting the network of channels consisting of ionic clusters (i.e., sulfonic acid moieties). [ABSTRACT FROM AUTHOR]

Diverse shapes (i.e. nanocube, nanowire, and nanosheet) of CH3NH3PbBr3 nanocrystals could be achieved by controlling thermodynamic (surface ligands) and kinetic (aging time, feed rate, and concentration) parameters for optimized design of optoelectronic properties and device development. [ABSTRACT FROM AUTHOR]

The additional (CH3NH3)2MnCl4 phase was observed upon increasing the Mn2+ dopant concentration, preventing the formation of Mn2+-doped CH3NH3PbCl3 NCs. We introduce an approach to avoid the formation of an impurity phase by switching the sequence for the addition of MnCl2 in the crystal growth process. [ABSTRACT FROM AUTHOR]

In this work, a fluorescence chemosensor based on organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoparticles has been investigated for the detection of volatile organic compounds (VOCs), aliphatic amines (monoethylamine, diethylamine, and trimethylamine). Perovskite films showed fast (<1 s), highly discernible (89%), and reversible/irreversible fluorescence quenching behavior in response to the amine vapor exposure. Detection mechanism was confirmed by crystalline structural analysis based on X-ray diffraction (XRD) measurements and quantum chemical calculations, which proved that fluorescence quenching originates from the structural conversion from perovskite to its components by reversible or irreversible hydrogen bonding interaction between perovskite and aliphatic amines. This study suggests a simple but very effective strategy for naked eye-based fluorescence sensing of the colorless and harmful aliphatic amine vapors. [ABSTRACT FROM AUTHOR]

In this work, we studied the interactions between organic-inorganic hybrid perovskite and polar aliphatic alcohols based on the absorption and photoluminescence changes of highly fluorescent CH 3 NH 3 PbBr 3 perovskite nanoparticles. Perovskite film gradually lost its yellow color and intense green emission in response to the aliphatic alcohol solvents. From the kinetic study of UV/Vis absorption changes and X-ray diffraction analysis, it was observed that optical properties of perovskite nanoparticles were linearly quenched by a polarity increase of aliphatic alcohols, concomitant with a conversion of crystalline structure. These results provide the insight into the origin of intrinsic instability of perovskites by polar molecules. Furthermore, sensitive response of perovskite nanoparticles to the polar molecules suggests a new practical strategy for colorimetric and fluorescent dual mode sensing of the molecule's polarity. [ABSTRACT FROM AUTHOR]

Organometal halide perovskites become important in the photovoltaic and light emitting devices due to the compositional flexibility with AMX3 formula (A is a monovalent organic ammonium cation; M is a metal ion; X is a halogen atom), imposing a significant demand to develop a synthetic route toward new types of nanocrystals. Although chemical pathways for perovskites nanoparticles were developed on the basis of the reprecipitation method, poor control of the nucleation and growth process results in a large size polydispersity that induces the ambiguities associated with a quantum confinement effect depending on their size. Here, a modified reprecipitation method is presented for the synthesis of CH3NH3PbBr3 perovskite nanoparticles with a controlled nanoparticle size by systematically tuning the feed ratio of the precursors. Fine control of the nanocrystal size provides new insights into the quantum confinement effect observed in microscale and nanoscale perovskite materials, where their energy bandgap is associated with the thickness of nanoparticles and invariant to preferential growth in a lateral dimension. [ABSTRACT FROM AUTHOR]

• Hydrazinium ligands electrostatically stabilize CsPbBr 3 nanocrystals. • Exciton-phonon coupling at CsPbBr 3 surface is significantly reduced by the N 2 H 5 Br. • Excess Br- anions improve the radiative recombination of CsPbBr 3 nanocrystals. • Short hydrazinium ligands improve the current efficiency of the CsPbBr 3 -LEDs. Electrically insulating organic ligands with long hydrocarbon chains cause bottlenecks, which hinder efficient charge injection and transportation in CsPbBr 3 nanocrystal (NC)-based light-emitting diodes (LEDs). Shorter ligand exchange with precise control of the surface ligand density through additional purification processes is a common strategy used to improve charge transport in optoelectronics. However, practical applications have been limited owing to poor structural integrity and colloidal stability associated with low steric hindrance of short surface-capping ligands. This study reports a post-synthesis treatment on CsPbBr 3 NCs using hydrazine monohydrobromide (N 2 H 5 Br; HZBr) containing NH 3 + cations, NH 2 groups, and Br− anions. Despite their short molecular structure, hydrazinium ligands produce a net positive charge at the NC surface, enhancing the colloidal dispersion of the CsPbBr 3 NCs through electrostatic stabilization. Cryogenic photoluminescence spectroscopic analysis identified that the exciton-phonon coupling at the surface of CsPbBr 3 NCs is significantly reduced by the presence of HZBr, preventing the formation of both permanent and transient exciton traps. Furthermore, enhanced surface stabilization to improve the radiative recombination was accomplished by excess Br− anions passivating Br− ion vacancies at the CsPbBr 3 NC surfaces. LEDs based on the HZBr-treated CsPbBr 3 NCs showed improved current efficiency of 12.16 cd/A, and the external quantum efficiency of 3.92% increased by a factor of 1.8, indicating enhanced hole-electron injection and transport into the CsPbBr 3 NCs. [ABSTRACT FROM AUTHOR]

A thermally stable 2D array of spheres and their morphology control become important for the fabrication of novel nanostructures. Here, a simple method is presented for fabrication of large-area and well-ordered arrays of carbonized polystyrene (PS) hollow spheres with a controlled (close-packed or non-close-packed hexagonal) morphology, prepared by combining the self-assembly of PS-grafted silica nanoparticles, etching, electron irradiation, and subsequent thermal annealing. Fine control in the 2D or 3D nanostructure of carbon materials can open up new opportunities for high-performance nanoscale applications that require an efficient fabrication method for preparation of the porous carbon array. [ABSTRACT FROM AUTHOR]

[Display omitted] • We demonstrated that sequential infiltration synthesis is a promising synthetic route for decorating the surface of NPs. • Changes in the polymer-grafted NP hybrid films were studied in terms of film swelling and chemical composition. • In situ FTIR spectroscopy was used to understand the distinctive growth mechanisms. • The terminal function groups of NPs and the functional groups of polymer matrix govern morphology of NP heterostructures. In this study, sequential infiltration synthesis (SIS) is demonstrated as a novel method for preparation of NP heterostructures with fine morphology tunability via a model system of SiO 2 –ZnO NP heterostructures. This approach is highly differentiated from conventional atomic layer deposition performed on NPs in that precursors are infiltrated into a polymer matrix, serving as a unique pathway for precursor diffusion, allowing all-around decoration of the NP surface. This approach also offers additional degrees of freedom for controlling the morphology of NP surface decoration with key engineering parameters: (1) terminal functional groups of NPs and (2) functional groups of a polymer matrix. Rational choices for both parameters with the desired reactivity to SIS precursors guide preferred entrapment or chemisorption sites for the precursors, directing the final morphologies of NP surface-decorating materials from patch layers to discrete atomic clusters. With rapid expansion of the library of materials that SIS can grow, this method opens a new venue for versatile and scalable fabrication of NP heterostructures. [ABSTRACT FROM AUTHOR]

Oleic acid has shown to accelerate the formation of (CH 3) 2 NH 2 ± cations in the colloidal solution, resulting in the morphological and phase transition of CH 3 NH 3 PbBr 3 to (CH 3) 2 NH 2 PbBr 3 via a reversible acid-base decomposition. Their phase and compositional stability can be significantly improved by introducing hydrazinium bromide that provides a strong Lewis base suppressing the deprotonation of CH 3 NH 3 ± cations as well as the excess Br- anions passivating Br- ion vacancies at the MHP NC surfaces, enhancing their optoelectronic properties as well as photostability. [Display omitted] • Phase transition of CH 3 NH 3 PbBr 3 to (CH 3) 2 NH 2 PbBr 3 occur via a reversible acid-base decomposition. • Deprotonated CH 3 NH 3 ± and the residual CH 3 NH 3 ± results in the formation of (CH 3) 2 NH 2 ±. • Oleic acid accelerates the formation of (CH 3) 2 NH 2 ± cations in the colloidal solution. • Hydrazinium bromide suppresses the deprotonation of CH 3 NH 3 ± cations. Organic acids, adopted in the conventional synthetic methods of metal halide perovskite (MHP) nanocrystals (NCs), have shown to accelerate the formation of (CH 3) 2 NH 2 ± cations in the colloidal solution, resulting in the morphological and phase transition of CH 3 NH 3 PbBr 3 to (CH 3) 2 NH 2 PbBr 3 via a reversible acid-base mediated decomposition. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analysis demonstrated the formation of (CH 3) 2 NH 2 ± and the complete removal of CH 3 NH 3 ± cations during the aging process of the colloidal MHP NCs when oleic acid was introduced as a common capping agent. Our results propose a dominant degradation pathway via the deprotonation of CH 3 NH 3 ± and the subsequent reaction with the residual CH 3 NH 3 ± by methyl group transfer, leading to the formation of (CH 3) 2 NH 2 ±. Meanwhile, their phase and compositional stability could be significantly improved by introduction of hydrazinium bromide that provides a strong Lewis base suppressing the deprotonation of CH 3 NH 3 ± cations. Furthermore, the excess Br- anions enable to passivate Br- ion vacancies at the MHP NC surface, which enhances their optoelectronic properties as well as photostability. Thus, these findings provide deep insight into the underlying chemistry associated with the degradation process in the colloidal MHP NCs, which is of fundamental importance for the use of highly stable and defect-free MHP NCs in the optoelectronic devices. [ABSTRACT FROM AUTHOR]

• Hydrazinium ligands improve the blue PL emission of CsPbBr 3 NPLs. • Exciton-phonon coupling at CsPbBr 3 surface is significantly suppressed by the HZBr. • HZBr treatment eliminated band tail states from lower defect levels in CsPbBr 3 NPLs. • HZBr-treated NPLs integrated into blue LED demonstrated a narrow emission peak. Metal-halide perovskites (MHPs) are promising materials for light-emitting diodes (LEDs) because of their high color purity, wide gamut, and low-cost processing. However, blue-emitting MHP LEDs exhibit low external quantum efficiencies because they are more susceptible to defect states with a larger energy bandgap compared to their green and red counterparts. Current strategies for achieving blue-emitting MHP LEDs involve compositional engineering; however, the ion migration of mixed halides imposes significant challenges related to abundant trap states. Therefore, in this study, we systematically investigated the effects of short organic and inorganic ligands with characteristic molecular structures and adjacent moieties on the optoelectronic characteristics of low-dimensional CsPbBr 3 nanoplatelets (NPLs) used as blue emitters in PeLEDs. Inorganic ligand (i.e., hydrazine monohydrobromide; HZBr) treatment achieved the most significant photoluminescence enhancement (∼10 fold) while preserving crystalline morphology and colloidal stability. Temperature-dependent photophysical properties reveal that HZBr treatment eliminates band tail states arising from lower defect levels in highly confined CsPbBr 3 NPLs. Therefore, it suppresses defect trapping and electron–phonon coupling, thereby reducing thermal quenching properties. The HZBr-treated NPLs were integrated into blue perovskite LEDs and demonstrated a narrow emission peak at 471 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Blue-emitting Zn-doped CsBr nanocrystals were synthesized by the hot-injection.. • Reactive acyl halides facilitate a preferential doping of metal cations into CsBr lattice. • Acyl halides possess stronger reactivity toward nucleophilic compounds. • Blue PL emission is attributed to the additional trap states of defects by Zn2+ doping. The potential route to induce effective metal doping into the colloidal nanocrystal (NC) lattice is still limited due to the unfavorable energy cost and needs further investigation for colloidal chemistry involved in the optical properties and device development with optimized NC design. In this study, we reports a bright blue emitting Zn2+-doped CsBr NCs (6.7 at.%) by introducing reactive benzoyl bromide to promote a preferential reaction with metal cations that are not favorably incorporated into the CsBr lattice. In particular, the acyl group (R-C = O-) of benzoyl bromide is more effective to adopt additional metal cations into the crystal lattice during the nucleation and growth process of colloidal CsBr NCs compared to alkylammonium bromides with long hydrocarbon chains, providing a new synthetic route for metal doping into the metal halide perovskites NCs. Zn2+-doped CsBr NCs exhibit a blue PL emission at 425 nm with a Stokes shift of 113 nm for the weak absorption band edge. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of colloidal orthorhombic Cs 2 ZnBr 4 and tetragonal Cs 3 ZnBr 5 nanocrystals. • Crystalline phase of Cs 2 ZnBr 4 and Cs 3 ZnBr 5 depending on reaction temperature. • A blue photoluminescence (PLQY ∼8.92 %) of tetragonal Cs 3 ZnBr 5 phase. • A significant sub-bands at 345 and 400 nm at the optical band edge. A framework to understand the effects of an oxide-ligand environment on the photoluminescence (PL) of rare-earth-element-doped oxynitride compounds is well established, whereas the effects of halide coordination on crystal field splitting and the associated PL emission are rarely studied. In this paper, we report a synthetic route to alkali metal halide NCs of Cs 2 ZnBr 4 and Cs 3 ZnBr 5 with a broad blue PL emission and large Stokes shift. In particular, the zero-dimensional Cs 3 ZnBr 5 phase, in which the isolated [ZnBr] 4 2− units were completely separated by surrounding Cs+ cations, exhibited a strong blue PL emission at 437 nm with a PL quantum yield of 8.92 %. The formation of additional trap states or defects in the Cs 3 ZnBr 5 crystalline lattice can be associated with a relatively considerable bands at 345 and 400 nm of the optical band edge, resulting in singlet-to-singlet transition of localized excitons with a short lifetime of 3.74 ns. Therefore, herein we demonstrate that tunable alkali metal halide NCs have considerable potential for optoelectronic applications. [ABSTRACT FROM AUTHOR]

• MAPbBr 3 nanocrystals doped with organometallic compounds and metal halides. • PL intensity of Cu-doped MAPbBr 3 nanocrystals was strongly quenched. • Simple strategy for fluorescence sensing of the heavy metal detection. Organic-inorganic hybrid perovskites have emerged as a promising material with excellent optoelectronic properties for applications in light harvesting and emitting devices. The doping of the bulk organohalide perovskites with homovalent or heterovalent metal cations has been performed to modify their energy band structure and the relevant optoelectronic properties. Here, we report the methylammonium lead bromide (MAPbBr 3) perovskite nanocrystals doped with organometallic compounds and metal halides, which were synthesized via a ligand-assisted ball-milling. In particular, the PL intensity of Cu-doped MAPbBr 3 nanocrystals was strongly quenched by three order of magnitude due to the significant charge trapping near the uncoordinated metallic Cu species. Furthermore, sensitive PL response of MAPbBr 3 nanocrystals to the metal cations suggests a simple and effective strategy for colorimetric and fluorescence sensing of the heavy metal detection in the organic solution phase. [ABSTRACT FROM AUTHOR]

A simple surface modification strategy to generate lithophilic sites in carbon-coated Si nanoparticles significantly enhances the capacity as well as cycling stability. [Display omitted] • A simple surface treatment process generates lithophilic surface groups on carbon-coated Si nanoparticles. • The surface-functionalized electrode of Si-C-AT shows a higher diffusion coefficient than Si-C. • The Si-C-AT shows a reversible capacity of 1575 mA h g−1 after 200 cycles at a current rate of 0.5C. • Functional groups on the Si-C-AT assist in accumulating the lithium-ions in excess on the carbon surface. Silicon nanoparticles (Si NPs) are potential anode materials for next-generation lithium-ion batteries due to their natural abundance, low discharge potential, and high theoretical capacity. Carbon coating improves the capacity of the Si NPs, protects them from disintegration during the lithiation/delithiation process, and provides an additional conductive matrix. Surface modification as a tool leading to capacity enhancement in carbon-coated Si NPs has rarely been explored. It is a straightforward process that involves the surface functionalization of carbon-coated Si NPs (Si-C) with the oxidizing acidic mixture. The surface-treated Si-C functionalized with carboxyl and hydroxyl groups in excess on the carbon surface of Si-C NPs. As a result of surface modification, the acid-treated Si-C (Si-C-AT) displayed a higher reversible capacity of 1575 mA h g−1 after 200 cycles compared to the Si-C (1261 mA h g−1) and bare Si (961 mA h g−1). This high capacity of Si-C-AT is a cumulative outcome of the functional groups and the disordered structure of the carbon shell. The functional groups act as lithophilic sites, and the disordered carbon shell facilitates the insertion-desertion of lithium ions. The simple surface modification strategy proposed in the present study significantly enhances the cyclability of the Si-C-AT NPs and has great potential for application in carbon-coated materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The recent trend in display fabrication using well-controlled composites containing phosphor requires achieving the desired property of their nanocomposites in accordance with the optoelectronic properties and morphological details of the constituent materials. While several approaches lead to good photostability of CsPbX 3 (X = Cl, Br, I) via proper encapsulation, practical deposition and patterning techniques require a complicated post-process to avoid the formation of considerable aggregates, cracks, and non-uniform packing during their drying process. Here, we report a new strategy to synthesize PMMA-grafted mesoporous SiO 2 nanoparticles (NPs) with infiltrated CsPbX 3 nanocrystals (NCs) by a solid-state reaction at high temperatures (300–800 °C) and subsequent surface-initiated atom transfer radical polymerization. The CsPbX 3 NCs embedded in the mesoporous SiO 2 NPs exhibited excellent photostability (photoluminescence intensity ∼100%) for more than 5 months under various polar solvents. In particular, PMMA brushes on the surface of CsPbX 3 -SiO 2 NPs provided improved wettability, leading to high polymeric processability and mechanical properties (elastic modulus = 3.99 GPa, hardness = 0.21 GPa) of PMMA-grafted CsPbX 3 -SiO 2 films. The combination of photostability and polymeric processability based on PMMA-grafted CsPbX 3 -SiO 2 NPs provides novel opportunities for low-cost and simple solution-processable multifunctional fluorescence materials in optoelectronics and biological imaging without severely compromising the auxiliary characteristics. PMMA-grafted CsPbBr 3 –SiO 2 nanoparticles provide not only distinct enhancement of the photostability in various chemical environments but also excellent processability and surface wettability in the process of film formation, which is a prerequisite for their practical application. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A new composition of red strontium aluminate phosphor (Sr4Al2O7:Eu3+, Eu2+) is synthesized using a solid state reaction method in air and in a reducing atmosphere. The investigation of firing temperature indicates that a single phase of Sr4Al2O7 is formed when the firing temperature is higher than 1300°C and that a Sr3Al2O6 phase is formed as the main peak below 1300°C. The effects of firing temperature and doping concentration on luminescent properties are investigated. Sr4Al2O7 phosphors exhibit the typical red luminescent properties of Eu3+ and Eu2+. A comparison photoluminescence study with Sr3Al2O6 phosphor shows that Sr4Al2O7 has higher emission intensity than Sr3Al2O6 as a result of the higher optimum doping concentration of Sr4Al2O7 phosphor. [Copyright &y& Elsevier]

Abstract: In this research, CuInS2 quantum dots (QDs) have been studied as an excellent red emitting source for white LED because of its non-toxic deep red emission, and large Stokes shift properties. The CuInS2 QDs are synthesized by the one-pot method, which is a candidate for the mass-production method. In addition, formation of ZnS shells on QD surfaces has been conducted in order to reduce non-radiative recombination on its surface defects. The photoluminescence (PL) characteristics of core/shell quantum dot show that the maximum PL wavelength blue-shifts by about 80nm on increasing its intensity more than 6 times. Quantum yield (QY) of the CuInS2/ZnS QDs shows about 67% as the maximum value. The dispersion of the quantum dots in polystyrene, which is hydrophobic and transparent, was also conducted using co-dispersing toluene. Finally, the polystyrene/quantum dot composite was applied on blue LEDs and it showed luminous efficacy of 10.7lm/W and (0.4338, 0.1827) CIE coordinates. [Copyright &y& Elsevier]