Differential effects of β-mercaptoethanol on CdSe/ZnS and InP/ZnS quantum dots

3D nanoprinting of semiconductor quantum dots by photoexcitation-induced chemical bonding

Three-dimensional (3D) laser nanoprinting allows maskless manufacturing of diverse nanostructures with nanoscale resolution. However, 3D manufacturing of inorganic nanostructures typically requires nanomaterial-polymer composites and is limited by a photopolymerization mechanism, resulting in a reduction of material purity and degradation of intrinsic properties. We developed a polymerization-independent, laser direct writing technique called photoexcitation-induced chemical bonding. Without any additives, the holes excited inside semiconductor quantum dots are transferred to the nanocrystal surface and improve their chemical reactivity, leading to interparticle chemical bonding. As a proof of concept, we printed arbitrary 3D quantum dot architectures at a resolution beyond the diffraction limit. Our strategy will enable the manufacturing of free-form quantum dot optoelectronic devices such as light-emitting devices or photodetectors.

The electrochemical reaction controlled optical response of cholestrol oxidase (COx) conjugated CdSe/ZnS quantum dots

This paper reports the enhanced performance of cholesterol oxidase (COx) conjugated CdSe/ZnS quantum dots (QDs) by using water-soluble mercaptoacitic acid (MAA) as linker. The functionalized MAA-CdSe/ZnS QDs conjugated in four different dilutions of cholesterol oxidase significantly affected QDs photoluminescence intensities, which affected the process of charge transfer from QDs to MAA. The conjugation of COx to MAA-QDs in increased dilutions resulted in the regain of PL intensities, which were attributed to the passivation of MAA HOMO/LUMO states. The electrochemical impedance spectroscopy and cyclic voltammetry of the conjugated QDs were performed to get study the charge transfer mechanism. The 1:1000 diluted COx conjugated MAA-CdSe/ZnS QDs was found to have the lowest charge transfer resistance of 228 Ω, the highest diffusion (~ 1.39 × 10^–13 cm²/s) and charge transfer rates (~ 4.5 × 10^–6 s⁻¹) between the electrode and the redox species. The current study demonstrated the sensitivity of electrochemical and optical based detection on the alkaline.

Strong room-temperature blue-violet photoluminescence of multiferroic BaMnF4

BaMnF4 microsheets have been prepared using a hydrothermal method. Strong room-temperature blue-violet photoluminescence has been observed (an absolute luminescence quantum yield of 67%) with two peaks located at 385 nm and 410 nm. More interestingly, photon self-absorption phenomenon has been observed, leading to an unusual abrupt decrease in the luminescence intensity at a wavelength of 400 nm. To understand the underlying mechanism of such emission, the electronic structure of BaMnF4 has been studied using first principles calculations. The observed two peaks are attributed to electron transitions between the upper-Hubbard bands of the Mn's t2g orbitals and the lower-Hubbard bands of the Mn's eg orbitals. The Mott gap mediated d-d orbital transitions may provide additional degrees of freedom to tune the photon generation and absorption in ferroelectrics.

UV-patternable nanocomposite containing CdSe and PbS quantum dots as miniaturized luminescent chemo-sensors

We have developed a patternable nanocomposite sensor based on luminescent CdSe QDs and a polyisoprene-based photoresist (PIP) as host matrix that showed chemosensing response against MET and EDA in vapour with a LOD around 0.1 pg and 15 ng, respectively.