Rapid and Large-Scale Preparation of Stable and Efficient White Light Emissive Perovskite Microcrystals Using Ionic Liquids

In this work, we report large-scale preparation of stable Sb3+ and Bi3+ codoped Cs2ZrCl6 microcrystals for highly efficient white light emission using ionic liquids, demonstrating a broad dual-band white emission covering 400–800 nm. The dual emissions originate from the associated self-trapped excitons of the [SbCl6]3– and [BiCl6]3– octahedra. Moreover, the ratio of the dual-emission peaks can be effectively regulated by tuning the excitation wavelength. Meanwhile, to improve the optical properties and stability, ionic liquids are employed to assist the synthesis process of perovskite materials. The white light emission of one of the samples demonstrates CIE coordinates right in the center of the white light region (0.334, 0.331) and an excellent color rendering index (∼90.3), accompanied by a 66.1% quantum efficiency. Moreover, our method allows the facile synthesis of large batches of microcrystalline powders. Our findings demonstrate the potential of white phosphors as single components for future applications in lighting fields

Unveiling Unconventional Luminescence Behavior of Multicolor Carbon Dots Derived from Phenylenediamine

Fluorescence regulation of carbon dots (CDs) during their preparation has become a hot research topic. In this work, multicolor fluorescent CDs with unconventional luminescence behavior are prepared by using o-, m-, or p-phenylenediamine (o-PD, m-PD, or p-PD, respectively) and 2,3-dihydroxynaphthalene with rich hydroxyl groups as reaction precursors. Tunable multicolor fluorescent CDs with bright blue, yellow, and red colors can be obtained by a solvothermal method under the joint action of ethanol and hydrochloric acid. The fluorescence emission of the synthesized CDs follows a rule of o-PD to m-PD to p-PD from blue to red, which is contrary to most previously reported results (the luminescence from blue to red following an order of m-PD to o-PD to p-PD). Our results reveal that the differences in the polymerization, surface states, functional groups, and graphite N content of CDs might be the main reasons for the unconventional luminescence behavior. In addition, these multicolor CDs have good applications in the fields of light-emitting diode lighting and anticounterfeiting

Ab Initio Molecular Dynamics of CdSe Quantum-Dot-Doped Glasses

We have probed the local atomic structure of the interface between a CdSe quantum dot (QD) and a sodium silicate glass matrix. Using ab initio molecular dynamics simulations, we determined the structural properties and bond lengths, in excellent agreement with previous experimental observations. On the basis of an analysis of radial distribution functions, coordination environment, and ring structures, we demonstrate that an important structural reconstruction occurs at the interface between the CdSe QD and the glass matrix. The incorporation of the CdSe QD disrupts the Na–O bonds, while stronger SiO4 tetrahedra are reformed. The existence of the glass matrix breaks the stable 4-membered (4MR) and 6-membered (6MR) Cd–Se rings, and we observe a disassociated Cd atom migrated in the glass matrix. Besides, the formation of Se–Na and Cd–O linkages is observed at the CdSe QD/glass interface. These results significantly extend our understanding of the interfacial structure of CdSe QD-doped glasses and provide physical and chemical insight into the possible defect structure origin of CdSe QD, of interest to the fabrication of the highly luminescent CdSe QD-doped glasses

Influence of Glass Composition on the Luminescence Mechanisms of CdSe Quantum-Dot-Doped Glasses

In this work, we characterized the electronic structure of CdSe quantum dots embedded in a series of x Na2O, (1–x) SiO2 glass matrices (x = 0, 0.25, 0.33, and 0.5). We analyzed the impact of the glass matrix composition on both the atomic structure of the quantum dot (QD) and the QD/glass interface, as well as the luminescence mechanisms, using density functional theory calculations. The increase of Na2O content in the glass matrices was found to promote the formation of Cd–O and Se–Na interfacial bonds and disrupt the Cd–Se bonds network. In particular, we show that the glass composition directly affects the nature of the highest occupied molecular orbitals (HOMO). According to the atomic structure, band gap distribution, and density of states calculation, we find that there is significant reconstruction of the QD and that the picture sometimes proposed of a “pristine quantum dot” surrounded by glass is not realistic. The introduction of CdSe QD significantly decreased the HOMO–LUMO gap of the glass compared to pristine glasses, and the interfacial bonds greatly contributed to the frontier orbitals without forming midgap states. We propose a new energy diagram, quite different from the traditional model, to explain the luminescence of CdSe quantum-dot-doped glasses, originating from the intrinsic emission of this hybrid system {QD + glass}. These results improve our understanding of the luminescence of CdSe quantum-dot-doped glasses, explaining the reason for the poor quantum efficiency and broad emission linewidth compared with their colloidal counterparts

Influence of Glass Composition on the Luminescence Mechanisms of CdSe Quantum-Dot-Doped Glasses

In this work, we characterized the electronic structure of CdSe quantum dots embedded in a series of x Na2O, (1–x) SiO2 glass matrices (x = 0, 0.25, 0.33, and 0.5). We analyzed the impact of the glass matrix composition on both the atomic structure of the quantum dot (QD) and the QD/glass interface, as well as the luminescence mechanisms, using density functional theory calculations. The increase of Na2O content in the glass matrices was found to promote the formation of Cd–O and Se–Na interfacial bonds and disrupt the Cd–Se bonds network. In particular, we show that the glass composition directly affects the nature of the highest occupied molecular orbitals (HOMO). According to the atomic structure, band gap distribution, and density of states calculation, we find that there is significant reconstruction of the QD and that the picture sometimes proposed of a “pristine quantum dot” surrounded by glass is not realistic. The introduction of CdSe QD significantly decreased the HOMO–LUMO gap of the glass compared to pristine glasses, and the interfacial bonds greatly contributed to the frontier orbitals without forming midgap states. We propose a new energy diagram, quite different from the traditional model, to explain the luminescence of CdSe quantum-dot-doped glasses, originating from the intrinsic emission of this hybrid system {QD + glass}. These results improve our understanding of the luminescence of CdSe quantum-dot-doped glasses, explaining the reason for the poor quantum efficiency and broad emission linewidth compared with their colloidal counterparts

Percolative Channels for Superionic Conduction in an Amorphous Conductor

All-solid-state batteries greatly rely on high-performance solid electrolytes. However, the bottlenecks in solid electrolytes are their low ionic conductivity and stability. Here we report a new series of amorphous xAgI·(1–x)Ag3PS4 (x = 0∼0.8 with interval of 0.1) conductors, among which the sample with x = 0.8 exhibits the highest ionic conductivity (about 1.1 × 10–2 S cm-1) and ultrahigh chemical stability. We discovered the existence of mixed disordered Ag3PS4 and AgI clusters in the amorphous conductors using solid-state nuclear magnetic resonance spectroscopy. The high ionic conductivity was ascribed to the formation of the interconnecting AgI clusters, i.e., the percolative channels for superionic conduction. The composition dependence of the ionic conductivity for this series of amorphous conductors was clarified by a continuum percolation model. These findings provide fundamental guidance for designing and fabricating high-performance amorphous solid electrolytes for all-solid-state batteries

Ab Initio Molecular Dynamics of CdSe Quantum-Dot-Doped Glasses

We have probed the local atomic structure of the interface between a CdSe quantum dot (QD) and a sodium silicate glass matrix. Using ab initio molecular dynamics simulations, we determined the structural properties and bond lengths, in excellent agreement with previous experimental observations. On the basis of an analysis of radial distribution functions, coordination environment, and ring structures, we demonstrate that an important structural reconstruction occurs at the interface between the CdSe QD and the glass matrix. The incorporation of the CdSe QD disrupts the Na–O bonds, while stronger SiO4 tetrahedra are reformed. The existence of the glass matrix breaks the stable 4-membered (4MR) and 6-membered (6MR) Cd–Se rings, and we observe a disassociated Cd atom migrated in the glass matrix. Besides, the formation of Se–Na and Cd–O linkages is observed at the CdSe QD/glass interface. These results significantly extend our understanding of the interfacial structure of CdSe QD-doped glasses and provide physical and chemical insight into the possible defect structure origin of CdSe QD, of interest to the fabrication of the highly luminescent CdSe QD-doped glasses

Efficient NiO Impregnated Walnut Shell-Derived Carbon for Dye-Sensitized Solar Cells

The conversion of biowaste into useful materials for technological uses has received a lot of interest in recent years. Here, a NiO@walnut shell (WS)-derived carbon composite (NiO@WS-derived carbon) was synthesized to be employed as an alternate counter electrode (CE) in dye-sensitized solar cells (DSSCs). The morphological studies demonstrated that NiO nanoparticles were uniformly impregnated into the WS-derived carbon frameworks. The electrochemical investigations showed that the NiO@WS-derived carbon composite CE displayed high catalytic activity and significant stability toward the I3–/I– redox couple after 100 CV cycles. The charge-transfer resistance of the NiO@WS-derived carbon composite CE (2.21 Ω) was also lower than that of the Pt-CE (3.04 Ω). The power conversion efficiency of the assembled DSSC with NiO@WS-derived carbon composite CE is 8.30%, which is comparable to Pt-CE (8.18%). NiO@WS-derived carbon composite CE is a possible alternative to the pricey Pt-CE in DSSC due to its low cost and excellent catalytic activity with acceptable stability

Tremendous Effect of the Morphology of Birnessite-Type Manganese Oxide Nanostructures on Catalytic Activity

The octahedral layered birnessite-type manganese oxide (OL-1) with the morphologies of nanoflowers, nanowires, and nanosheets were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric/differential scanning calorimetry (TG/DSC), Brunnauer–Emmett–Teller (BET), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS). The OL-1 nanoflowers possess the highest concentration of oxygen vacancies or Mn3+, followed by the OL-1 nanowires and nanosheets. The result of catalytic tests shows that the OL-1 nanoflowers exhibit a tremendous enhancement in the catalytic activity for benzene oxidation as compared to the OL-1 nanowires and nanosheets. Compared to the OL-1 nanosheets, the OL-1 nanoflowers demonstrate an enormous decrease (ΔT50 = 274 °C; ΔT90 > 248 °C) in reaction temperatures T50 and T90 (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation. The origin of the tremendous effect of morphology on the catalytic activity for the nanostructured OL-1 catalysts is experimentally and theoretically studied via CO temperature-programmed reduction (CO-TPR) and density functional theory (DFT) calculation. The tremendous catalytic enhancement of the OL-1 nanoflowers compared to the OL-1 nanowires and nanosheets is attributed to their highest surface area as well as their highest lattice oxygen reactivity due to their higher concentration of oxygen vacancies or Mn3+, thus tremendously improving the catalytic activity for the benzene oxidation

Percolative Channels for Superionic Conduction in an Amorphous Conductor

All-solid-state batteries greatly rely on high-performance solid electrolytes. However, the bottlenecks in solid electrolytes are their low ionic conductivity and stability. Here we report a new series of amorphous xAgI·(1–x)Ag3PS4 (x = 0∼0.8 with interval of 0.1) conductors, among which the sample with x = 0.8 exhibits the highest ionic conductivity (about 1.1 × 10–2 S cm-1) and ultrahigh chemical stability. We discovered the existence of mixed disordered Ag3PS4 and AgI clusters in the amorphous conductors using solid-state nuclear magnetic resonance spectroscopy. The high ionic conductivity was ascribed to the formation of the interconnecting AgI clusters, i.e., the percolative channels for superionic conduction. The composition dependence of the ionic conductivity for this series of amorphous conductors was clarified by a continuum percolation model. These findings provide fundamental guidance for designing and fabricating high-performance amorphous solid electrolytes for all-solid-state batteries