Wafer-level detection of organic contamination by ZnO-rGO hybrid-assisted laser desorption/ionization time-of-flight mass spectrometry.

A technique for wafer-level detection of organic contaminations via surface-assisted laser desorption/ionization time-of-flight mass spectrometry was developed. To replace the organic matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, zinc oxide-reduced graphene oxide (ZnO-rGO) hybrid was prepared by a hydrothermal reaction and used as the matrix in the detection of benzo[a]pyrene (B[a]P). By varying the rGO content and the amount of hybrid, the optimal rGO content in the hybrid for the detection of B[a]P was determined to be 4 wt% and the optimal amount of hybrid was 20 ng.

Fabrication of highly luminescent and concentrated quantum dot/poly(methyl methacrylate) nanocomposites by matrix-free methods.

We present matrix-free methods for fabricating highly luminescent and transparent CdSe/ZnS quantum dot (QD)/polymer nanocomposites utilizing poly(methyl methacrylate) (PMMA)-grafted QDs with various molecular weights. We found that the QD-PMMA nanocomposites prepared by these matrix-free methods were superior to those prepared by a simple blending method in relation to their optical property, QD dispersion, and quantum efficiency (QE). In particular, a matrix-free nanocomposite containing PMMA with a molecular weight of 2000 had the highest QE (52.

Quantum efficiency of colloidal suspensions containing quantum dot/silica hybrid particles.

We have investigated the fluorescence properties of colloidal suspensions conntaining quantum dot (QD)/silica hybrid particles. First, we synthesized QD/silica hybrid particles with silica-QD-silica (SQS) core-shell-shell geometry, and monitored the quantum efficiencies of their suspensions at various particle concentrations. We found that the quantum efficiency (QE) of SQS particles in deionized (DI) water was much lower than that of the QDs even at low particle concentration, mainly due to the light scattering of emitted photons at the silica/water interface, followed by reabsorption by QDs.

Fabrication of high quantum yield quantum dot/polymer films by enhancing dispersion of quantum dots using silica particles.

We have fabricated quantum dot (QD)/polymer films of high quantum yield by coating silica particles with quantum dots. When particles were dispersed in tetrahydrofuran, free QD suspension exhibited higher quantum yield than QD-coated silica particles. Scattering is a most likely reason for the drop in quantum yield for the QD-coated silica particles, as supported by results of silica particles with varying morphologies: for example, QD-coated hollow silica particles showed higher quantum yield than filled silica particles, as the hollowness gave rise to reduced scattering.