Why do similar 1D-polyhedron-chain copper chloride semiconductors have 2-order-distinct luminescence quantum efficiencies?

The "green" copper halides with one-dimensional polyhedron chains are very interesting novel semiconductors. These weakly interacting parallel quantum wires (1D polyhedron chains) play key roles in their photophysical properties. Unlike Cs3Cu2I5, which has been much investigated, its homologous compounds Cs3Cu2Cl5 and CsCu2Cl3 remain less studied and their properties are controversial.

Highly stoichiometry-deviating chalcopyrite quantum dots: synthesis and copper defects-correlated photophysical properties.

Copper indium selenide (CISe) is a prototype infrared semiconductor with low toxicity and unique optical characteristics. Its quantum dots (QDs) accommodate ample intrinsic point defects which may actively participate in their rather complex photophysical processes. We synthesize CISe QDs with similar sizes but with distinct highly stoichiometry-deviating atomic ratios.

Critical Roles of Octahedron Bilayer Surface/Interior Bromide Defects in Photodynamics of Multi-Quantum-Well-Structured Cesium Bismuth Bromide.

We investigate theoretically the roles of the intrinsic point defects in the photophysics of wide-bandgap multi-quantum-well-structured CsBiBr based on the Shockley-Read-Hall statistics and multiphonon recombination theory. The plus Bethe-Salpeter equation calculation reveals that there is a prominent exciton peak below the interband absorption edge, and it clarifies the experimental debate. The most energetically favorable native defects possess deep thermodynamic transition levels.

Highly Thermally Sensitive Cascaded Wannier-Mott Exciton Ionization/Carrier Localization in Manganese-Doped Perovskite Nanocrystals.

Transition-metal doping in perovskite nanocrystals strongly alters the photophysical properties of these nanocrystals. However, the details of the underlying thermal and optical processes within such an intriguing symmetry-breaking nanosystem are far from clear. Herein, we study the sensitively temperature-dependent and highly competent delocalized exciton and transition-metal ion-captured carrier recombination processes in manganese-doped CsPbBrCl nanocrystals.

Cooccurrence of pH-sensitive shifting blue and immobile green triple surface-state fluorescence in ultrasmall super body-centered cubic carbon quantum dots.

Carbon quantum dots are widely used in various fields owing to excellent optical properties and outstanding biocompatibility. We synthesize rare super body-centered cubic (C) structured carbon quantum dots by using cheap source materials and simple preparation method. They exhibit one shifting blue emission band and two close immobile green bands.

Resonant defect recombination-localized surface plasmon energy transfer and exciton dominated fluorescence in ZnO-Au-ZnO multi-interfaced heteronanocrystals.

The semiconductor-metal heteronanocrystals (HNCs) that possess a perfect epitaxial interface can accommodate novel and interesting physical phenomena owing to the strong interaction and coupling between the semiconductor excitons and metal plasmons at the interface. Here, we fabricate the pyramidal ZnO-Au HNCs and study their unique photophysical properties. Several Au nanospheres are perfectly epitaxially bound with a single ZnO NC owing to the small lattice mismatch between them and there are also ZnO-Au-ZnO sandwiched HNCs.

Native surface oxidation yields SiC-SiO core-shell quantum dots with improved quantum efficiency.

Silicon carbide is an important wide-bandgap semiconductor with wide applications in harsh environments and its applications rely on a reliable surface, with dry or wet oxidation to form an insulating layer at temperatures ranging from 850 to 1250 °C. Here, we report that the SiC quantum dots (QDs) with dimensions lying in the strong quantum confinement regime can be naturally oxidized at a much lower temperature of 220 °C to form core/shell and heteroepitaxial SiC/SiO QDs with well crystallized silica nanoshells. The surface silica layer enhances the radiative transition rate of the core SiC QD by offering an ideal carrier potential barrier and diminishes the nonradiative transition rate by reducing the surface dangling bonds, and, as a result, the quantum yield is highly improved.

One-Center and Two-Center Self-Trapped Excitons in Zero-Dimensional Hybrid Copper Halides: Tricolor Luminescence with High Quantum Yields.

The organic-inorganic hybrid copper halides exhibit intriguing and complex photophysical properties, and the underlying mechanisms are far from clear. Here, we study the photodynamics of six novel types of low-dimensional hybrid copper halides, which have a maximum quantum yield of 98.6%.

Origin of proton induced fluorescence quenching of colloidal carbon dots: reshaping of Schrödinger wavefunctions and huge red shift of transition energy.

The fluorescence quenching by protons is a universal phenomenon but the mechanism remains unclear. Here, we take the fluorescent amide-terminated carbon dots as a prototype to study the proton fluorescence quenching mechanism by using both experiments and time-dependent density functional theory calculations. The study reveals that when an approached proton is captured by the weakly negatively charged fluorophore group of the colloidal carbon dot, it will substantially change the electron wavefunctions owing to the strong proton-electron interaction, and this leads to highly diminished energy gap and resultant fluorescence quenching in the visible spectral region.

Fabry-Perot Mode-Limited High-Purcell-Enhanced Spontaneous Emission from Laser-Induced CsPbBr Quantum Dots in CsPbBr Microcavities.

The patterned metal halide perovskites exhibit novel photophysical properties and high performance in photonic applications. Here, we show that a UV continuous wave laser can induce crystallization of individual and patterned CsPbBr quantum dots (QDs) inside the CsPbBr microplatelets. The microplatelet acts as a natural Fabry-Perot cavity and causes the high-Purcell-effect-enhanced (by 287 times) cavity mode spontaneous emission of the embedded CsPbBr QDs.

Role of Polyhedron Unit in Distinct Photophysics of Zero-Dimensional Organic-Inorganic Hybrid Tin Halide Compounds.

The zero-dimensional (0D) metal halides comprising isolated metal-halide polyhedra are the smallest inorganic quantum systems and accommodate quasi-localized Frenkel excitons with unique photophysics of broadband luminescence, huge Stokes shift, and long lifetime. Little is known about the role of polyhedron type in the characteristics of 0D metal halides. We comparatively study three novel kinds of 0D hybrid tin halides having identical organic groups.

Influence of crystallization temperature on fluorescence of n-diamond quantum dots.

Nanodiamonds are popular biological labels because of their superior mechanical and optical properties. Their surfaces bridging the core and surrounding medium play a key role in determining their bio-linkage and photophysical properties. n-diamond is a mysterious carbon allotrope whose crystal structure remains debated.

Critical Roles of High- and Low-Frequency Optical Phonons in Photodynamics of Zero-Dimensional Perovskite-like (CHNCl)SnCl Crystals.

The zero-dimensional perovskites composed of isolated polyhedrons have unique and distinct physical properties compared with three-dimensional perovskites composed of interconnected polyhedrons. Here, we study the photodynamics of the zero-dimensional perovskite-like (CHNCl)SnCl single crystals composed of isolated [SnCl] tetrahedrons. They exhibit red luminescence with huge Stokes shift (2.

Interaction between indium tin oxide nanoparticles and ferricytochrome c: Conformation, redox state, and adsorption scheme.

The conformations and redox states of ferricytochrome c, before and after adsorption onto the surface of the indium tin oxide (ITO) nanoparticles, are studied to reveal the interaction nature between the cytochrome c and the conducting metal oxide surface. The characterizations with resonance Raman scattering and UV-Vis absorption reveal that the change of pH at moderate ionic strength induces transitions of conformations and redox-states, which suggests that there is intramolecular electron transfer. The conformations of the cytochrome c species are maintained after adsorption onto or collision with the ITO surface, but the redox states change significantly, and the change depends on the surface structure of the ITO nanoparticle.

Giant photoluminescence enhancement in SiC nanocrystals by resonant semiconductor exciton-metal surface plasmon coupling.

We report giant fluorescence enhancement in SiC nanocrystals (NCs) embedded in a sodium dodecyl sulfonate dielectric medium by proximately contacted Ag nanoparticles. The enhancement in integrated fluorescence intensity reaches an astonishing 176-fold under 360 nm excitation (53.3-fold enhancement in emission maximum intensity).

Highly bright tunable blue-violet photoluminescence in SiC nanocrystal-sodium dodecyl sulfonate crosslinked network.

We report strong photoluminescence in an ultra-small surface oxidized SiC quantum dot-sodium dodecyl sulfonate crosslinked network. The peak emission wavelength is tunable spanning a wide blue-violet spectral region showing clear quantum confinement effects. The photoluminescence decay exhibits triple recombination dynamics with an average lifetime of 13.

Group IV nanoparticles: synthesis, properties, and biological applications.

In this review, the emerging roles of group IV nanoparticles including silicon, diamond, silicon carbide, and germanium are summarized and discussed from the perspective of biologists, engineers, and medical practitioners. The synthesis, properties, and biological applications of these new nanomaterials have attracted great interest in the past few years. They have gradually evolved into promising biomaterials due to their innate biocompatibility; toxic ions are not released when they are used in vitro or in vivo, and their wide fluorescence spectral regions span the near-infrared, visible, and near-ultraviolet ranges.

Synthesis and low-temperature photoluminescence properties of SnO2 nanowires and nanobelts.

Ultra-long rutile tin dioxide nanowires and nanobelts are synthesized by thermal oxidation of tin powder using gold film as the catalyst. Nanowire or nanobelts can be selectively produced by tuning the reaction temperature. The vapour-liquid-solid growth mechanism is proposed.