Thang Phan Nguyen

MoS2-Nanosheet/Graphene-Oxide Composite Hole Injection Layer in Organic Light-Emitting Diodes

In this work, composite layers comprising two-dimensional MoS2 and graphene oxide (GO) were employed as hole injection layers (HILs) in organic light-emitting diodes (OLEDs). MoS2 was fabricated by the butyllithium (BuLi) intercalation method, while GO was synthesized by a modified Hummers method. The X-ray diffraction patterns showed that the intensity of the MoS2 (002) peak at 14.15° decreased with increase in GO content; the GO (001) peak was observed at 10.07°. In the C 1s synchrotron radiation photoemission spectra, the contributions of the C-O, C=O, and O-C=O components increased with increase in GO content. These results indicated that GO was well mixed with MoS2. The lateral size of MoS2 spanned from a few hundreds of nanometers to 1 μm, while the size of GO was between 400 nm and a few micrometers. Thus, the coverage of the MoS2-GO composite on the ITO surface improved as the GO content increased, owing to the large particle size of GO. Notably, GO with large size could fully cover the indium tin oxide film surface, thus, lowering the roughness. The highest maximum power efficiency (PEmax) was exhibited by the OLED with MoS2-GO 6:4 composite HIL, indicating that similar contents of MoS2 and GO in MoS2-GO composites provide the best results. The OLED with GO HIL showed very high PEmax (4.94 lm W−1) because of very high surface coverage and high work function of GO. These results indicate that the MoS2-GO composites can be used to fabricate HILs in OLEDs.

Facile synthesis of CsPbBr3/PbSe composite clusters

Abstract In this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs:Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots.

Synthesis of fluorescent silicon quantum dots for ultra-rapid and selective sensing of Cr(VI) ion and biomonitoring of cancer cells

A facile one-step synthetic approach was developed for fabrication of fluorescent silicon quantum dots (Si QDs) and used as a probe for fluorescence detection of hexavalent chromium (Cr (VI)) in environmental water samples. The as-prepared Si QDs exhibit a strong fluorescence emission peak at 520 nm with a quantum yield of 14.2%. The fluorescent Si QDs were rapidly produced by using ascorbic acid as a reductant at 55 °C. The emission peak of Si QDs at 420 nm was effectively quenched upon the addition of Cr(VI). The Si QDs acted as the best fluorescent probe for the detection of Cr(VI) at PBS pH 7.4. The developed probe possessed a good linear correlation (R2 = 0.992) between Cr(VI) concentration (1.25-40 μM) and the (F0-F)/F0 values with a detection limit of 0.65 μM. Furthermore, the Si QDs served as a bio-probe for fluorescence imaging of A549 lung cancer cells and cell viability results confirmed the good biocompatible nature of Si QDs. The as-fabricated Si QDs show several advantages such as rapidity, selectivity and biocompatibility for sensing of Cr(VI) and imaging of A549 cells, which opens a facile analytical platform for environmental and bioimaging applications.

Gold-copper nanoshell dot-blot immunoassay for naked-eye sensitive detection of tuberculosis specific CFP-10 antigen

Herein, a straightforward and highly specific dot-blot immunoassay was successfully developed for the detection of Mycobacterium tuberculosis antigen (10 kDa culture filtrate protein, CFP-10) via the formation of copper nanoshell on the gold nanoparticles (AuNPs) surface. The principle of dot-blot immunoassay was based on the reduction of Cu2+ ion on the GBP-CFP10G2-AuNPs conjugates, which has gold binding and antigen binding affinities, simultaneously, favouring to appear red dot that can be observed with naked-eye. The dot intensity is proportional to the concentration of tuberculosis antigen CFP-10, which offers a detection limit of 7.6 pg/mL. The analytical performance of GBP-CFP10G2-AuNPs-copper nanoshell dot-blot was superior than that of conventional silver nanoshell. This method was successfully applied to identify the CFP-10 antigen in the clinical urine sample with high sensitivity, specificity, and minimized sample preparation steps. This method exhibits great application potential in the field of nanomedical science for highly reliable point-of-care detection of CFP-10 antigen in real samples to early diagnosis of tuberculosis.

Facile Solution Synthesis of Tungsten Trioxide Doped with Nanocrystalline Molybdenum Trioxide for Electrochromic Devices

A facile, highly efficient approach to obtain molybdenum trioxide (MoO3)-doped tungsten trioxide (WO3) is reported. An annealing process was used to transform ammonium tetrathiotungstate [(NH4)2WS4] to WO3 in the presence of oxygen. Ammonium tetrathiomolybdate [(NH4)2MoS4] was used as a dopant to improve the film for use in an electrochromic (EC) cell. (NH4)2MoS4 at different concentrations (10, 20, 30, and 40 mM) was added to the (NH4)2WS4 precursor by sonication and the samples were annealed at 500 °C in air. Raman, X-ray diffraction, and X-ray photoelectron spectroscopy measurements confirmed that the (NH4)2WS4 precursor decomposed to WO3 and the (NH4)2MoS4–(NH4)2WS4 precursor was transformed to MoO3-doped WO3 after annealing at 500 °C. It is shown that the MoO3-doped WO3 film is more uniform and porous than pure WO3, confirming the doping quality and the privileges of the proposed method. The optimal MoO3-doped WO3 used as an EC layer exhibited a high coloration efficiency of 128.1 cm2/C, which is larger than that of pure WO3 (74.5 cm2/C). Therefore, MoO3-doped WO3 synthesized by the reported method is a promising candidate for high-efficiency and low-cost smart windows.