Important role of surface plasmon coupling with the quantum wells in a surface plasmon enhanced color-converting structure of colloidal quantum dots on quantum wells.

To improve the color-conversion efficiency based on a quantum-well (QW) light-emitting diode (LED), a more energy-saving strategy is needed to increase the energy transfer efficiency from the electrical input power of the LED into the emission of over-coated color-converter, not just from LED emission into converted light. In this regard, the efficiency of energy transfer of any mechanism from LED QW into the color-converter is an important issue. By overlaying blue-emitting QW structures and GaN templates with both deposited metal nanoparticles (DMNPs) and color-converting quantum dot (QD) linked synthesized metal nanoparticles (SMNPs) of different localized surface plasmon (LSP) resonance wavelengths for producing multiple surface plasmon (SP) coupling mechanisms with the QW and QD, we study the enhancement variations of their internal quantum efficiencies and photoluminescence decay times. By comparing the QD emission efficiencies between the samples with and without QW, one can observe the advantageous effect of QW coupling with LSP resonances on QD emission efficiency. Also, with the LSP resonance wavelengths of both DMNPs and SMNPs close to the QW emission wavelength for producing strong SP coupling with the QW and hence QD absorption, a higher QD emission or color-conversion efficiency can be obtained.

Emission behaviors of colloidal quantum dots linked onto synthesized metal nanoparticles.

With two different residual surfactants, four different metal nanoparticles (NPs), including two Au NPs and two Ag NPs are synthesized for linking with red-emitting CdZnSeS/ZnS colloidal quantum dots (QDs) to enhance QD emission efficiency. Those metal NPs are first connected with amino polyethylene glycol thiol of different molecular weights to avoid aggregation and make them positively charged. They can attract negatively charged QDs for inducing surface plasmon (SP) coupling such that either QD absorption or emission and hence overall color conversion efficiency can be enhanced. The enhancement of QD emission efficiency is evaluated through the comparison of time-resolved photoluminescence behaviors under different QD linkage conditions. Such results are confirmed by the measurement of the emission quantum efficiency of QD. It is found that by linking QDs onto Ag NPs, the QD emission efficiency is more enhanced, when compared with Au NPs. Also, depending on the synthesis process, the residual surfactant of citrate leads to a relatively large increment in QD emission efficiency, when compared to the surfactant of cetrimonium chloride. A more enhanced QD emission efficiency is caused by a higher QD linkage capability and a stronger SP coupling effect.

Color conversion efficiency enhancement of colloidal quantum dot through its linkage with synthesized metal nanoparticle on a blue light-emitting diode.

Four surface-modified and, hence, positively charged metal nanoparticles (NPs) of different localized surface plasmon (LSP) resonance wavelengths are synthesized for linking with negatively charged, red-emitting colloidal CdZnSeS/ZnS quantum dots (QDs) on the top surface of a blue-emitting InGaN/GaN quantum well (QW) light-emitting diode (LED) through electro-static force. The metal NP-QD linkage leads to a short distance between them for producing their strong surface plasmon (SP) coupling, such that QD absorption and emission can be enhanced. Meanwhile, the small p-GaN thickness in the LED results in strong SP coupling between the LSP resonance of metal NP and the QWs of the LED, leading to enhanced QW emission and, hence, stronger QD excitation. All those factors together result in the increase of the color conversion efficiency of the QD.

Efficiency enhancement of light color conversion through surface plasmon coupling.

The efficiency enhancement of light color conversion from blue quantum well (QW) emission into red quantum dot (QD) emission through surface plasmon (SP) coupling by coating CdSe/ZnS QDs on the top of an InGaN/GaN QW light-emitting diode (LED) is demonstrated. Ag nanoparticles (NPs) are fabricated within a transparent conductive Ga-doped ZnO interlayer to induce localized surface plasmon (LSP) resonance for simultaneously coupling with the QWs and QDs. Such a coupling process generates three enhancement effects, including QW emission, QD absorption at the QW emission wavelength, and QD emission, leading to an overall enhancement effect of QD emission intensity. An Ag NP geometry for inducing an LSP resonance peak around the middle between the QW and QD emission wavelengths results in the optimized condition for maximizing QD emission enhancement. Internal quantum efficiency and photoluminescence (PL) decay time measurements are performed to show consistent results with LED performance characterizations, even though the QD absorption of PL excitation laser may mix with the SP-induced QD absorption enhancement effect in PL measurement.

Effect of SGLT2 inhibitors versus DPP4 inhibitors on major and non-major osteoporotic fracture risks among general and high-risk type 2 diabetes patients: A nationwide retrospective cohort study.

AIMS: To retrospectively analyze the association of sodium-glucose cotransporter-2 inhibitors (SGLT2is) versus dipeptidyl peptidase-4 inhibitors (DPP4is) with a range of major and non-major fracture events, and explore heterogeneous treatment effect among high-risk patient subgroups. METHODS: Newly stable SGLT2i or DPP4i users in 2017 were identified in Taiwan's National Health Insurance Research Database and followed up until a fracture occurred, loss of follow-up, death, or December 31, 2018, whichever came first. Outcomes included composite major and non-major fractures and individual components in major fractures. Cox model and restricted mean survival time (RMST) analyses were utilized to assess the treatment effect on fractures. RESULTS: 21,155 propensity-score-matched SGLT2i and DPP4i users were obtained. Over 2 years, the hazard ratio and RMST difference for major fracture with SGLT2i versus DPP4i use were 0.89 (95% CI, 0.80, 1.00) and 1.51 (-0.17, 3.17) days, respectively, and those for non-major fracture with SGLT2i versus DPP4i use were 0.89 (0.81, 0.98) and 2.44 (0.47, 4.37) days, respectively. A 180-day lag time analysis for fracture outcomes showed consistent results with primary findings. A SGLT2is-associated harmful effect on major fractures (but not on non-major fractures) was observed among female patients and those with a diabetes duration of ≥ 8 years, prior fractures, and established osteoporosis. CONCLUSION: This study adds supporting real-world evidence for SGLT2is-associated bone safety for a wide range of fractures, which promotes the rational use of SGLT2is in routine care and highlights the importance of the close monitoring of patients with high fracture risks to maximize treatment benefits while reducing undesirable effects.