Xudong Guo

Intracellular Fluorescent Temperature Probe Based on Triarylboron Substituted Poly N-Isopropylacrylamide and Energy Transfer

A novel hydrophilic fluorescence temperature probe (PNDP) based on polarity-sensitive triarylboron compound (DPTB) and PNIPAM is designed and synthesized. In order to overcome the shortcomings of the single-intensity-based sensing mechanism and obtain more robust signals, ratiometric readout is achieved by designing an efficient FRET system (PNDP-NR) between DPTB and Nile Red (NR). PNDP-NR possesses some excellent features, including wide temperature range, good linear relationship, high temperature resolution, excellent reversibility, and stability. Within a sensing temperature range of 30-55 °C, the fluorescence color of PNDP-NR experiences significant change from red to green-blue. PNDP-NR is also introduced into NIH/3T3 cells to sense the temperature at the single-cell level. It gave excellent photostability and low cytotoxicity in vivo.

Molecular Engineering of Aqueous Soluble Triarylboron-Compound-Based Two-Photon Fluorescent Probe for Mitochondria H2S with Analyte-Induced Finite Aggregation and Excellent Membrane Permeability.

Hydrogen sulfide (H2S) is a multifunctional signaling molecule that participates in many important biological processes. Herein, by functionalizing triarylboron with cyclen and diphenylamine, we synthesized TAB-1, TAB-2, and TAB-3 for H2S recongnization by rational design of molecular structures. Among them, aqueous soluble TAB-2 possesses excellent properties, including large two-photon action cross section, membrane permeability and can effectively complex with Cu(2+). The complex of TAB-2-Cu(2+) can selectively detect H2S with an instant response and mitochondria targeted. Moreover, the H2S-induced finite aggregation of indicators enhances their photostability and causes variation of the fluorescence lifetime. TAB-2-Cu(2+) has also been successfully applied for the mitochondria H2S imaging in NIH/3T3 fibroblast cells by TPM and FLIM.

Near-infrared broadband luminescence in Bi2O3-GeO2 binary glass system

Near-infrared broadband luminescence from 1100 to 1600 nm was observed in Bi2O3-GeO2 binary glasses. The strongest emission can be observed with 30 mol % Bi2O3 when pumped at 808 nm. The lifetimes of all samples are longer than 200 μs. The glass network was studied by Raman spectra and Bi+ ions are proposed as the infrared luminescence centers in this glass system. Thermal treatment in air results in partly oxidation of Bi+ to Bi2+.

Magnetically driven negative thermal expansion in antiperovskite Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3)

Negative thermal expansion (NTE) was investigated for Ga1−xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3). As x increases, the temperature range where lattice contracts upon heating becomes broad and shifts to lower temperatures. The coefficient of linear thermal expansion beyond −40 ppm/K with a temperature interval of ∼50 K was obtained around room temperature in x = 0.2 and 0.25. Local lattice distortion which was thought to be intimately related to NTE is invisible in the X-ray pair distribution function of x = 0.3. Furthermore, a zero-field-cooling exchange bias was observed as a result of competing ferromagnetic (FM) and antiferromagnetic (AFM) orders. The concomitant FM order serves as an impediment to the growth of the AFM order, and thus broadens the temperature range of NTE. Our result suggests that NTE can be achieved in antiperovskite manganese nitrides by manipulating the magnetic orders without distorting the local structure.

Size effects on negative thermal expansion in cubic ScF3

Scandium trifluoride (ScF3), adopting a cubic ReO3-type structure at ambient pressure, undergoes a pronounced negative thermal expansion (NTE) over a wide range of temperatures (10 K–1100 K). Here, we report the size effects on the NTE properties of ScF3. The magnitude of NTE is reduced with diminishing the crystal size. As revealed by the specific heat measurement, the low-energy phonon vibrations which account for the NTE behavior are stiffened as the crystal size decreases. With decreasing the crystal size, the peaks in high-energy X-ray pair distribution function (PDF) become broad, which cannot be illuminated by local symmetry breaking. Instead, the broadened PDF peaks are strongly indicative of enhanced atomic displacements which are suggested to be responsible for the stiffening of NTE-related lattice vibrations. The present study suggests that the NTE properties of ReO3-type and other open-framework materials can be effectively adjusted by controlling the crystal size.

Luminescent properties of benzothiazole derivatives and their application in white light emission

Three benzothiazole derivatives, N-[4-(benzothiazol-2-yl)-3-hydroxyphenyl]-octanamide (BHPO1), N-[3-(benzothiazol-2-yl)-4-hydroxyphenyl]-octanamide (BHPO2), N-[4-(benzothiazol-2-yl)phenyl]-octanamide (BPO) were prepared and their luminescence properties were investigated. These analogues show similar absorption maxima but quite different emission regions due to the existence of an excited-state intramolecular proton transfer (ESIPT) process in BHPO1 and BHPO2. Upon excitation with 365 nm light, BPO, BHPO1 and BHPO2 exhibit bright blue-violet, green and orange emission in aggregated states, respectively which perfectly make up the component elements of white light. By doping these compounds into a polymer matrix at a certain proportion, an emission that lies at the saturated white-light region with CIE chromaticity coordinates of (0.31, 0.32) was obtained. This study provides a flexible and simple fabrication process of a white-light emitting device using three structurally-similar compounds without detrimental energy transfer.

Strong ferromagnetism beyond the mechanism of uncompensated surface spins in nanocrystalline GaCMn3

Weak ferromagnetism arising from uncompensated surface spins (USS) is usually expected when an antiferromagnetic (AFM) material is diminished to nanoscale in size. Here we report strong ferromagnetism beyond the USS-mechanism in the AFM ground state of nanocrystalline GaCMn3. The enhanced ferromagnetism can be attributed to an AFM to ferromagnetic (FM) transformation in the shell with a finite thickness of a crystallite. As the average crystallite size ( ) decreases, the FM shell expands relative to the AFM core, leading to strengthening ferromagnetism. Through the AFM/FM interface the rotation of FM spins under a magnetic field is impeded by the AFM spins, leading to a large coercivity (HC). The largest HC (∼6.4 kOe at 5 K) was observed in the sample with a critical of ∼15 nm. In contrast, USS-type weak ferromagnetism was observed in nanocrystalline GaNMn3. Our results suggest a new approach to achieving strong FM order beyond the prediction of the USS mechanism, as well as to designing AFM-core/FM-shell nanostructures based on nanosized AFM materials.

A hydrophilicity-based fluorescent strategy to differentiate cysteine/homocysteine over glutathione both in vivo and in vitro

An easily-prepared probe/nanogel composite indicator HTBNM/PU was presented, which showed selective fluorescence responses to cysteine/homocysteine over glutathione both in vivo and in vitro based on the different hydrophilicity of these biothiols. In principle, this approach could endow any lipophilic thiol indicator with selectivity for sulfur-containing amino acids.

Preparation of transparent monolithic methylsilsesquioxane (MSQ) aerogels via ambient pressure drying

Monolithic methylsilsesquioxane (MSQ) aerogels have been prepared from methyltrimethoxysilane (MTMS) via an ambient pressure drying (APD) method. Tetraethylammonium hydroxide (TEAH) was used to suppress macroscopic phase separation and accelerate the condensation reaction. The obtained hydrophobic MSQ aerogels are highly transparent and withstand exposure to aggressive media for extended periods of time. This novel anti-corrosion property can be further improved by chemical modification with POTS and PDTS.

Specific Imaging of Tyrosinase in Vivo with 3-Hydroxybenzyl Caged D-Luciferins

Tyrosinase (TYR), a key enzyme in biosynthesis of melanin, usually functions as a biomarker of severe skin diseases such as vitiligo and melanoma cancer. Accurate detection of TYR activity in vivo is urgent but still challenging. Inspired by the advantages of bioluminescence in vivo strategy in imaging and the specific hydroxylation of 3-hydroxybenzyloxy group by TYR, a bioluminogenic probe, TYR-LH2, was designed and synthesized through caging D-luciferin with 3-hydroxybenzyl. The probe exhibits high selectivity and sensitivity toward TYR with a detection limit of 0.11 U/mL in a small detection volume of 100 μL. Bioluminescence imaging results show that TYR-LH2 is fully competent for monitoring the dynamic changes of TYR in living cells and model animals and possesses the capability of discriminating melanocytes from other cell lines, thus offering a promising approach for investigation and diagnosis of melanoma cancer and other TYR-related diseases in vivo.