Waste Polyethylene-Derived Carbon Dots: Administration of Metal-Free Oxidizing Agents for Tunable Properties and Photocatalytic Hyperactivity.

The possibility of converting waste plastics into carbon dots (CDs) with 100% efficiencies using KMnO has emerged as a significant discovery in mitigating plastic pollution and upcycling. However, the lack of tunability of their properties, viz. aerial O harvesting, light-induced autophagy, and photoactivity using air as a free oxidant, has remained a bottleneck.

The dark exciton ground state promotes photon-pair emission in individual perovskite nanocrystals.

Cesium lead halide perovskites exhibit outstanding optical and electronic properties for a wide range of applications in optoelectronics and for light-emitting devices. Yet, the physics of the band-edge exciton, whose recombination is at the origin of the photoluminescence, is not elucidated. Here, we unveil the exciton fine structure of individual cesium lead iodide perovskite nanocrystals and demonstrate that it is governed by the electron-hole exchange interaction and nanocrystal shape anisotropy.

Dynamics of Photo-Generated Carriers across the Interface between CsPbBr Nanocrystals and Au-Ag Nanostructured Film, and Its Control via Ultrathin MgO Interface Layer.

The dynamics and control of charge transfer between optoelectronically interesting and size-tunable halide perovskite quantum dots and other juxtaposed functional electronic materials are important issues for the emergent device interest involving such a family of materials in heterostructure configurations. Herein, we have grown bimetallic Au-Ag thin films on glass by pulsed laser deposition at room temperature, which bear nanoparticulate character, and the corresponding optical absorption spectra reveal the expected surface plasmon resonance signature(s). Subsequently, spin-coated CsPbBr nanoparticle films onto the bimetallic Au-Ag films exhibit surface-enhanced Raman scattering as well as strong photoluminescence quenching, the latter reflecting highly efficient transfer of photo-generated carriers across the CsPbBr/Au-Ag interface.

Postsynthesis Mn-doping in CsPbI nanocrystals to stabilize the black perovskite phase.

Long term stability of the black perovskite phase of CsPbI3 nanocrystals under ambient conditions is an important challenge for their optoelectronic applications in real life. The nanocrystalline size is found to improve the stability of the black phase at room temperature. Furthermore, doping Mn is proposed to improve the stability of the black perovskite phase of CsPbI3 nanocrystals (NCs).

Quantum dot-induced phase stabilization of α-CsPbI3 perovskite for high-efficiency photovoltaics.

We show nanoscale phase stabilization of CsPbI quantum dots (QDs) to low temperatures that can be used as the active component of efficient optoelectronic devices. CsPbI is an all-inorganic analog to the hybrid organic cation halide perovskites, but the cubic phase of bulk CsPbI (α-CsPbI)-the variant with desirable band gap-is only stable at high temperatures. We describe the formation of α-CsPbI QD films that are phase-stable for months in ambient air.

Terahertz Conductivity within Colloidal CsPbBr3 Perovskite Nanocrystals: Remarkably High Carrier Mobilities and Large Diffusion Lengths.

Colloidal CsPbBr3 perovskite nanocrystals (NCs) have emerged as an excellent light emitting material in last one year. Using time domain and time-resolved THz spectroscopy and density functional theory based calculations, we establish 3-fold free carrier recombination mechanism, namely, nonradiative Auger, bimolecular electron-hole recombination, and inefficient trap-assisted recombination in 11 nm sized colloidal CsPbBr3 NCs. Our results confirm a negligible influence of surface defects in trapping charge carriers, which in turn results into desirable intrinsic transport properties, from the perspective of device applications, such as remarkably high carrier mobility (∼4500 cm(2) V(-1) s(-1)), large diffusion length (>9.

Excellent green but less impressive blue luminescence from CsPbBr3 perovskite nanocubes and nanoplatelets.

Green photoluminescence (PL) from CsPbBr3 nanocubes (∼11 nm edge-length) exhibits a high quantum yield (>80%), narrow spectral width (∼85 meV), and high reproducibility, along with a high molar extinction coefficient (3.5 × 10(6) M(-1) cm(-1)) for lowest energy excitonic absorption. In order to obtain these combinations of excellent properties for blue (PL peak maximum, λ max < 500 nm) emitting samples, CsPbBr3 nanocubes and nanoplatelets with various dimensions were prepared.

Origin of Unusual Excitonic Absorption and Emission from Colloidal Ag2S Nanocrystals: Ultrafast Photophysics and Solar Cell.

Colloidal Ag2S nanocrystals (NCs) typically do not exhibit sharp excitonic absorption and emission. We first elucidate the reason behind this problem by preparing Ag2S NCs from nearly monodisperse CdS NCs employing cation exchange reaction. It was found that the defect-related midgap transitions overlap with excitonic transition, blurring the absorption spectrum.

Colloidal CsPbBr3 Perovskite Nanocrystals: Luminescence beyond Traditional Quantum Dots.

Traditional CdSe-based colloidal quantum dots (cQDs) have interesting photoluminescence (PL) properties. Herein we highlight the advantages in both ensemble and single-nanocrystal PL of colloidal CsPbBr3 nanocrystals (NCs) over the traditional cQDs. An ensemble of colloidal CsPbBr3 NCs (11 nm) exhibits ca.

Electronic grade and flexible semiconductor film employing oriented attachment of colloidal ligand-free PbS and PbSe nanocrystals at room temperature.

Electronic grade semiconductor films have been obtained via the sintering of solution processed PbS and PbSe nanocrystals at room temperature. Prior attempts to achieve similar films required the sintering of nanocrystals at higher temperatures (>350 °C), which inhibits the processing of such films on a flexible polymer substrate, and it is also expensive. We reduced the sintering temperature by employing two important strategies: (i) use of ligand-free nanocrystals and (ii) oriented attachment of nanocrystals.

Citrate-hydrazine hydrogen-bonding driven single-step synthesis of tunable near-IR plasmonic, anisotropic silver nanocrystals: implications for SERS spectroscopy of inorganic oxoanions.

A simplified, single-step aqueous synthesis route to tunable anisotropic silver nanocrystals (NCs) has been developed by tailoring the hydrogen-bonding interactions between a mild stabilizer, sodium citrate, and a mild reductant, hydrazine hydrate. The structure directing ability of the H-bonding interaction was harnessed by keeping a stoichiometric excess of hydrazine under ambient conditions (pH 7, 25 °C). Decreasing the synthesis temperature to 5 °C imparts rigidity to the citrate-hydrazine H-bonding network, and the plasmon peak moves from 500 to 550 nm (using 40 mM hydrazine).

Organic-free colloidal semiconductor nanocrystals as luminescent sensors for metal ions and nitroaromatic explosives.

Exposed surfaces of organic-free colloidal semiconductor nanocrystals act as generic luminescent sensors for multiple analytes. S(2-) capped CdSe/CdSeS/CdS core/gradient-shell/shell nanocrystals are turn-on sensors for Cd(2+) ions (110 pM) in an aqueous medium with physiological pH 7.4.