Ultrastable Luminescent Organic-Inorganic Perovskite Quantum Dots via Surface Engineering: Coordination of Methylammonium Bromide and Covalent Silica Encapsulation.

Encapsulation of luminescent perovskite quantum dots (QDs) into a solid matrix has been approved to be an efficient way to improve their stability. In this work, we reported a green encapsulation method to produce ultrastable CH3NH3PbBr3 QDs incorporated into the SiO2 matrix. Specifically, fresh-prepared CH3NH3PbBr3 QDs were covalently embedded into silica by an aqueous sol-gel method assisted with CH3NH3Br, which not only effectively inhibited the water-driven degradation of QDs through surface coordination, but also strongly stabilized the QDs in solid powder via concentration gradient. As far as we know, this silica encapsulation of perovskite QDs in aqueous environments is reported for the first time. Luminescent properties of perovskite QDs during the course of gelation as well as in resulting composite powder were investigated using steady-state and time-resolved spectroscopies, and a 2 wt % QD-doped sample treated with 11.5 mM of CH3NH3Br was demonstrated to be the optimal phosphor. The green-emissive phosphor had a PLQY of 60.3% and a full width at half maxima of ∼25 nm, exhibiting ultrahigh stability tested by cycle heating (120 °C), continuous heating (80 °C, 60 h), and light irradiation (450 nm light, 350 h). The phosphor was readily blended with polymers and applied as a color-converting layer on blue light-emitting diodes.

A fluorescent nanoprobe for real-time monitoring of intracellular singlet oxygen during photodynamic therapy.

Sensing of intracellular singlet oxygen (1O2) is required in order to optimize photodynamic therapy (PDT). An optical nanoprobe is reported here for the optical determination of intracellular 1O2. The probe consists of a porous particle core doped with the commercial 1O2 probe 1,3-diphenylisobenzofuran (DPBF) and a layer of poly-L-lysine. The nanoparticle probes have a particle size of ~80 nm in diameter, exhibit good biocompatibility, improved photostability and high sensitivity for 1O2 in both absorbance (peak at 420 nm) and fluorescence (with excitation/emission peaks at 405/458 nm). Nanoprobes doped with 20% of DPBF are best suited even though they suffer from concentration quenching of fluorescence. In comparison with the commercial fluorescent 1O2 probe SOSG, 20%-doped DPBF-NPs (aged) shows higher sensitivity for 1O2 generated at an early stage. The best nanoprobes were used to real-time monitor the PDT-triggered generation of 1O2 inside live cells, and the generation rate is found to depend on the supply of intracellular oxygen. Graphical abstract A fluorescent nanoprobe featured with refined selectivity and improved sensitivity towards 1O2 was prepared from the absorption-based probe DBPF and used to real-time monitoring of the generation of intracellular 1O2 produced during PDT.

In situ silica coating-directed synthesis of orthorhombic methylammonium lead bromide perovskite quantum dots with high stability.

Luminescent perovskite quantum dots (QDs) had attracted great attention by virtue of the merits of color-tunable and narrow-band emissions. However, sofar reported perovskite QDs suffered from instability more or less. In this work, a type of silica-coated orthorhombic CH3NH3PbBr3 QDs (SiO2-QDs) with greatly improved stability was reported. The SiO2-QDs were one-pot synthesized using a reprecipitation-encapsulation method assisted with an amine functional silane, which not conly controlled the crystallization of QDs, but also encapsulated QDs with a silica layer simultaneously. More interestingly, the in situ encapsulation of silica shell induced the presence of orthorhombic perovskite that was thought to be unstable at room temperature. This is the first report of orthorhombic CH3NH3PbBr3 QDs, as far as we are concerned. The orthorhombic SiO2-QDs exhibited narrow-band green luminescence with a quantum yield of 78%, and a high production yield of ∼70wt%. Moreover, stability of SiO2-QDs was considerably improved due to silica-coating. White-LEDs were also successfully fabricated with the green SiO2-QDs and a red commercial phosphors using a noncontact configuration. These results demonstrated that the orthorhombic SiO2-QDs held great promise for high-performance display or lighting technology.

Demonstration of multi-wavelength tunable fiber lasers based on a digital micromirror device processor.

Based on a digital micromirror device (DMD) processor as the multi-wavelength narrow-band tunable filter, we demonstrate a multi-port tunable fiber laser through experiments. The key property of this laser is that any lasing wavelength channel from any arbitrary output port can be switched independently over the whole C-band, which is only driven by single DMD chip flexibly. All outputs display an excellent tuning capacity and high consistency in the whole C-band with a 0.02 nm linewidth, 0.055 nm wavelength tuning step, and side-mode suppression ratio greater than 60 dB. Due to the automatic power control and polarization design, the power uniformity of output lasers is less than 0.008 dB and the wavelength fluctuation is below 0.02 nm within 2 h at room temperature.

[The Study on the Far-FTIR and THz Spectra of Azitromycin Drugs with Different Physical Forms].

Far Fourier transform infrared spectroscopy (Far-FTIR) and terahertz time-domain spectroscopy (THz-TDS) were used to measure the fingerprint spectra of Azitromycin suspension, capsule, tablet and dispersible tablet under vacuum and nitrogen conditions, respectively. In the frequency range of 0.2-15 THz, highly resolved spectral features for Azitromycin suspension were measured and some minor differences were observed between domestic and exotic Azitromycin Suspension, such as linewidth broadening and additional peaks. As same time, for the domestic Azitromycin capsule, tablet and dispersible tablet, the absorption baselines in the range of 0.2-2.7 THz rise with the increase of frequency while absorption peaks become weaker due to the scattering of bigger particles and smaller amount of Azitromycin. Also, the additional peaks are caused by the absorption of filling materials. In parallel with the qualitative measurement, the THz absorption spectra for mixtures of polyethylene (PE) powders and exotic Azithomycin suspension with different concentrations were also measured. According to the linear correlation between the concentration and the absorption intensity, the concentration of effective component can be evaluated accurately. This means that THz-TDS method is suitable for the quality inspection and evaluation of the mixed Azithromycin system.