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Highly luminescent, multiply passivated green‐ and red‐light‐emitting quantum dots are used as color converters in InGaN blue LEDs to achieve external quantum efficiencies of 72% and 34%, respectively. White QD‐LEDs prepared for a display backlight are shown to have an efficacy of 41 lm W−1 and color reproducibility of 100% compared to the NTSC standard in CIE 1931. Finally, a 46 inch LCD TV panel (see image) using the QD‐LED backlight is successfully demonstrated for the first time.

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There is an urgent demand to improve the efficiency and the color purity of the environment-friendly quantum dots (QDs), which can be used in wide color gamut (WCG) displays. In this study, we optimized the reaction conditions for the InP core synthesis and the ZnSe/ZnS multishell growth on the core. As a result, remarkable improvements were achieved in the photoluminescence quantum yield (PL QY, 95%) and the full width at half-maximum (fwhm, 36 nm), with perfectly matched wavelength (528 nm) for the green color in WCG displays. Injection of the phosphorus precursor at a mild temperature during the InP core synthesis reduced the size distribution of the core to 12%, and the shell growth performed at a high temperature significantly enhanced the crystallinity of the thick passivating layer. We also investigated the photophysical properties, particularly the energy trap distributions and trap state emissions of the InP-based QDs with different shell structures. The time-resolved and temperature-dependent PL spectra clearly indicated that the well-passivated InP/ZnSe/ZnS QDs showed nearly trap-free emissions over a wide temperature range (77–297 K). Also, the on- and off-time probability on single QD blinking and Auger ionization efficiencies also showed that these QDs were hardly affected by the surface traps.

MicroRNA (miRNA) is an important small RNA which regulates diverse gene expression at the post-transcriptional level. miRNAs are considered as important biomarkers since abnormal expression of specific miRNAs is associated with many diseases including cancer and diabetes. Therefore, it is important to develop biosensors to quantitatively detect miRNA expression levels. Here, we develop a nanosized graphene oxide (NGO) based miRNA sensor, which allows quantitative monitoring of target miRNA expression levels in living cells. The strategy is based on tight binding of NGO with peptide nucleic acid (PNA) probes, resulting in fluorescence quenching of the dye that is conjugated to the PNA, and subsequent recovery of the fluorescence upon addition of target miRNA. PNA as a probe for miRNA sensing offers many advantages including high sequence specificity, high loading capacity on the NGO surface compared to DNA and resistance against nuclease-mediated degradation. The present miRNA sensor allowed the detection of specific target miRNAs with the detection limit as low as ~1 pM and the simultaneous monitoring of three different miRNAs in a living cell.

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Considerable research has been carried out on colloidal semiconductor nanocrystals (NCs) on account of their size dependent electronic and optical properties, which are the key issues in many applications, such as biomedical fluorophores, 1 LEDs, 2 and photovoltaic devices. 3 Among them, a group of II-VI semiconducting NCs, for example, CdSe quantum dots (QDs), exhibit excellent photostability, quan-tum yield (QY), and a tunable emission wavelength. 4,16 However, CdSe QDs have limited applications owing to their intrinsic toxicity. 5 It is believed that III-V QDs, particularly InP NCs, are the most desirable alternative. However, the photoluminescent quantum yield tends to be very low due to nonradiative surface recombination sites and high activation barriers for carrier detrapping. 6,7 A core-shell structure appears to be essential for surface passivation, but limited numbers have been reported, including InP/ZnS 8,9,14,15 and InP/ZnCdSe 10 core/shell QDs. HF etching 11,13 and low reaction temperature methods have also been attempted. In particular, the recent reports by Peng's group on highly luminescent InP/ZnS core-shell quantum dots in the visible range using fatty amine 9 and Reiss on the one-pot synthesis of InP/ZnS 14 are quite impressive.We report the stepwise synthesis of InP/ZnS core-shell quantum dots and the role of zinc acetate during the reaction. Zinc acetate was used as a precursor for zinc and acetic acid. Highly luminescent InP/Zn-palmitate was obtained as an intermediate. The InP core was synthesized with indium acetate (In(OAc) 3 ), tris(trimethylsilyl)phosphine ((TMS) 3 P), and palmitic acid as the indium and phosphorus precursors

The colloidal quantum dots (QDs) have inherent multiple dangling bonds (DBs) on the surface atoms due to the intrinsic weak bonding nature and steric hindrance of organic ligands. Such DBs can be the trap sites for charge carriers, leading to the reduction of luminescence efficiency, but their detailed characteristics are still unclear. In this study, we disclose the electronic and optical features of the surface DBs of InP QDs via density functional calculations combined with experimental evidence. For InP core, both In-DB and P-DB create invariant DB energy levels with respect to the core size, and their optical transition intensities exhibit an order of magnitude smaller than the band-edge transition. The In-DB and P-DB generate a deep trap level at −3.947 eV and a shallow trap level at −5.717 eV, and the deep trap level corresponds to the origin to induce the trap emissions. The passivation with ZnS shell on InP core significantly modifies the optical properties of both DBs to the radiative transition even when the passivating shell partially covers the InP surface. The ZnS shell growth pushes the energy levels of the In-DB and P-DB to near the band edges and makes the orbitals more delocalized. Such modified roles of the DBs significantly improve the optical intensities comparable to those of the band-edge transition, which is validated by the absorption calculations and luminescence measurements.