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Symmetric quadrupolar molecules generally exhibit apolar ground states and dipolar excited states in a polar environment, which is explained by the excited state evolution from initial charge delocalization over all molecules to localization on one branch of the molecules after a femtosecond pulse excitation. However, direct observation of excited-state charge redistribution (delocalization/localization) is hardly accessible. Here, the intramolecular charge delocalization/localization character of a newly synthesized acceptor-donor-acceptor molecule (ADA) has been intensively investigated by femtosecond stimulated Raman scattering (FSRS) together with femtosecond transient absorption (fs-TA) spectroscopy. By tracking the excited state Raman spectra of the specific alkynyl (-C≡C-) bonds at each branch of ADA, we found that the nature of the relaxed S1 state is strongly governed by solvent polarity: symmetric delocalized intramolecular charge transfer (ICT) characters occurred in apolar solvent, whereas the asymmetric localized ICT characters appeared in polar solvent because of solvation. The solvation dynamics of ADA extracted from fs-TA is consistent with the time constants obtained by FSRS, but the FSRS clearly tracks the excited state intramolecular charge transfer delocalization/localization.

A novel solid-state Z-scheme photocatalyst Ag3PO4/CSs/AgBr (carbon spheres, CSs) was rationally designed and successfully synthesized via a facile hydrothermal coprecipitation reaction. AgBr and Ag3PO4 were effectively loaded on the surface of the CSs and Ag3PO4/CSs/AgBr showed wide visible light absorption and superior photocatalytic performance. On the basis of ultraviolet photoelectron spectroscopy (UPS) analysis and scavenger reactions, a possible photocatalytic reaction mechanism for Ag3PO4/CSs/AgBr is proposed. The CSs act as a charge carrier transfer bridge for constructing the all-solid-state Z-scheme photocatalyst. The photogenerated electrons from Ag3PO4 and holes from AgBr congregate and recombine in the CSs phase, leaving photogenerated electrons with strong reduction abilities in the conduction band (CB) of AgBr and holes with strong oxidation abilities in the valence band (VB) of Ag3PO4. Some Ag+ ions accept electrons and turn to Ag nanoparticles (NPs), leading to the surface plasmon resonance of Ag NPs on AgBr. Therefore, the photocatalytic performance and stability were significantly improved.

In recent years, ionic liquids (ILs) have received increasing attention because of low vapor pressure, environment friendliness, good thermal and chemical stability and strong solubility. However, the liquid nature and high viscosity restrict their applications in some fields. Encapsulation of ILs is an attractive way to handle them easily. Herein, we proposed a facile method to prepare IL-loaded microcapsules using IL-in-oil emulsion as template, poly(amide-thioether) as surfactant and interfacial thiol–isocyanate click reaction for shell formation. In this system, core materials ILs were proved to be able to catalyze thiol–isocyanate reaction without side products, which significantly simplified the preparation process of microcapsules. The shell of the microcapsules was composed of polythiourethane and poly(amide-thioether), which provided a strong protection for ILs. In addition, compared with IL-in-water emulsion, the application of IL-in-oil emulsion avoided the side reactions of the highly active isocyanate. The IL content of the resulted microcapsules could reach as high as 70 wt.%. It was also demonstrated that the proposed encapsulation technology was suitable for ILs with different polarities. This work provides an efficient way to encapsulate ILs using emulsion template, which will make ILs find widespread applications across various fields.

A novel microcapsule-type thermal latent curing agent with a double-shell structure was successfully fabricated. 1-Benzyl-2-methylimidazole (1B2MZ) was encapsulated by poly(methyl methacrylate-n-butyl acrylate) (PMMA/BA) using the solvent evaporation method, which served as the primary microcapsules (PMCs) to be deposited by polydopamine (PDA). Various glass transition temperatures (Tg, from 116.7 to 57.2 °C) and thermal properties of shell material PMMA/BA were obtained by tuning the mass ratio of BA to MMA monomer. PMMA/BA with 20 wt% of BA ratio was selected as the shell of PMCs for its appropriate Tg (92.33 °C) and relatively good thermal resistance. (Decomposition temperature was 222.83 °C.) The obtained PMCs and the double-shell microcapsules (DMCs) had good spherical shape, and the chemical structure of DMCs was confirmed by Fourier transform infrared spectra. Thermogravimetric analysis indicated that the core contents of PMCs and DMCs were 11.95 and 11.37%, respectively. After being coated by PDA, the solvent resistances of microcapsules in weak-polar (toluene) and high-polar (dichloromethane, DCM and acetone) solvents were significantly improved. When storing at room temperature for more than 4 months, the mixture of DMCs and the diluted epoxy could be cured at 120 °C for 1 h.

Ternary Ag–TiO2–SiO2 nanocomposite photocatalysts were synthesized via a facile sol–gel method and characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, surface area analyzer (BET method) and UV-diffuse reflectance spectroscope, respectively. The results indicated that the crystallite size of TiO2 reduced after being doped by SiO2 and Ag, while the agglomeration and phase transition of TiO2 nanoparticles were restrained, resulting in the greatly increased specific surface area of Ag–TiO2–SiO2. Moreover, the adsorption edge of TiO2 obviously red-shifted from UV to visible light range, indicating the higher utilization of solar energy. The photocatalytic performance was evaluated by the degradation of phenol under visible light (λ > 420 nm) irradiation. The degradation rate of phenol over 1%Ag–TiO2–SiO2 reached 91.1% after illumination for 180 min, which was significantly higher than that of TiO2. This work provided a simple method to prepare highly active TiO2-based photocatalysts.

The synthesis and characterization of a pair of pentafluorosulfanylated styrenic polymers and their subsequent application in nonvolatile organic field-effect transistor (OFET) memory devices are reported. The unusual pentafluorosulfanyl (SF5) functional group is unique in that it possesses a strong dipole moment that arises from both inductive and resonance effects but is at the same time highly hydrophobic. This intriguing chemical moiety also presents steric bulk that is comparable to a tert-butyl group. Exploiting these intrinsic physicochemical properties, the use of pentafluorosulfanylated styrenic polymers as the electret layer of nonvolatile OFET-based memory devices is reported. Aside from being the first examples of SF5-functionalized styrenic polymers, the reported materials also display excellent thermal stability, moderately large memory windows and retention times, and stable reversibilities spanning multiple PGM/ERS cycles.

Given the outstanding room-temperature phosphorescence (RTP) of Mn–ZnS quantum dots (QDs) and the specific recognition performance of the aptamer, we built phosphorescent composites from aptamers conjugated with polyethyleneimine quantum dots (PEI-QDs) and applied them to cytochrome c (Cyt c) detection. Specifically, QDs/CBA composites were generated from the electrostatic interaction between the positively-charged PEI-QDs and the negatively-charged Cyt c binding aptamer (CBA). With the presence of Cyt c, the Cyt c can specifically bind with the QDs/CBA composites, and quench the RTP of QDs through photoinduced electron-transfer (PIET). Thereby, an optical biosensor for Cyt c detection was built, which had a detection range of 0.166–9.96 μM and a detection limit of 0.084 μM. This aptamer-mediated phosphorescent sensor with high specificity and operational simplicity can effectively avoid the interference of scattering light from complex substrates. Our findings offer a new clue for building biosensors based on QDs and aptamers.

Two bismuth–organic network polymers were synthesized by means of a one-step polycondensation reaction between an aromatic dithiol/trithiol and triphenylbismuth. The materials were characterized by solid-state UV–vis spectroscopy, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, elemental microanalysis, and thermogravimetric analysis. Uniform dispersion of the hydrophobic and water-insoluble bismuth-containing polymers in aqueous media was achieved by the addition of 2 kDa poly(ethylene glycol) methyl ether thiol. This enabled quantitative phantom imaging experiments on a clinical computed tomography (CT) scanner, which showed that the coordination polymers possessed strong CT contrast properties. The observed X-ray attenuation properties of each coordination polymer were correlated with its bismuth payload. The X-ray opacity, thermal and chemical stabilities, and aqueous dispersibility of this novel class of bismuth–organic materials make them potentially useful as biomedical CT contrast agents and radiopaque materials.

Nacre-mimetic strategy provides an enlightening approach to design high-performance bioinspired nanocomposites. Yet, it is still a big challenge to integrate excellent mechanical properties and tunable multifunctionality into artificial nacre materials. Herein, we develop a pioneering strategy to simultaneously modulate the electrical conductivity and mechanical properties of nacre-mimetic nanocomposite films by controlling interlay supramolecular interactions. A series of novel waterborne polyurethanes with 2-ureido-4[1H]-pyrimidinone (UPy) quadruple hydrogen bonding motifs in the side-chains were elaborately designed and synthesized, and further assembled with Ti3C2Tx MXene nanosheets to construct lamellar nacre-mimetic nanocomposite films with highly ordered nanostructure. This research revealed for the first time that merely varying the content of UPy groups on polyurethane realize significant modulation of mechanical properties, electrical conductivity, and even the electromagnetic shielding effectiveness of nacre-mimetic nanocomposites. Strikingly, the tensile strength of the nanocomposites can be improved from 87.91 to 136.96 MPa and the electrical conductivity from 3214.0 to 4136.1 S cm−1 when the UPy content is increased from 0 to 15%. Additionally, the nacre-mimetic nanocomposite film is capable of fast responsive Joule heating performance at low trigger voltage. This work would open up a new avenue for fabricating multifunctional and mechanically robust biomimetic nanocomposites.

Hydroxyl (OH) play an essential role in atmospheric chemistry. OH radical is an indicator of atmospheric oxidation and self-purification, which determines the removal of most trace gases in the atmosphere, such as CO, SO2, NO2, CH4 and other volatile organic compounds (VOCs). A ground-based system for measurement of tropospheric OH radical by Laser Induced Fluorescence technique (AIOFM-LIF) was developed and integrated into a mobile observation platform for field observation. Ambient air expands through a 0.4 mm nozzle to low pressure. OH radical is irradiated by the 308 nm laser pulse at a repetition rate of 8.5 kHz, accompanying the release fluorescence of the A2Σ+(v’=0)—X2Πi(v’’=0) transition at 308 nm with the resultant fluorescence being detected by gated photon counting. The detection sensitivity of AIOFM-LIF system was calibrated by a portable standard OH radical source based on water photolysis-ozone actinometry. Following laboratory and field calibrations to characterise the instrument sensitivity, OH radical detection limits were (1.84±0.26) × 105 cm-3 and (3.69±0.52) × 105 cm-3 at night and noon, respectively. During “A comprehensive STudy of the Ozone foRmation Mechanism in Shenzhen” (STORM) campaign, AIOFM-LIF system was deployed in Shenzhen, China, and OH radical concentration was obtained validly except for the rainy days. Mean diurnal variation of HOx radical concentration was obtained, and the peak was 6.6×106 cm-3 which appeared around 12:00 at noon. A general good agreement of OH radical concentration with j(O1D) was observed with a high correlation (R2 =0.77), which illustrates that photolysis of ozone is an important source of OH radical during this campaign. A box model was applied to simulate the concentrations of OH at this field site, the primary production of OH radical was generally dominated by photolysis of O3, HONO, HCHO, while the other production was contributed by calculated species (OVOCs).

Mechanically robust superhydrophobic coatings have been extensively reported using chemically susceptible inorganic fillers like SiO2, TiO2, ZnO, etc. for constructing micro-nano structures. Organic particles are good candidates for improving chemical resistance, whereas the synthesis of organic particles with well-defined and stable micro-nano structures remains exclusive. Here, an all-organic, cross-linked superhydrophobic coating comprising raspberry-like fluorinated micro particles (RLFMP) and fluorinated polyurethane (FPU) was prepared via thiol-click reaction. Benefiting from the robust micro-nano structure of RLFMP and the excellent flexibility of FPU, the coating could maintain superhydrophobic after severe alkali corrosion or mechanical damage, while the superhydrophobicity could be repaired readily by the fast recovery of micro-nano roughness and migration of branched fluoroalkyl chains to the coating surface. Our design strategy is expected to provide a good application of thiol-click chemistry. This article is protected by copyright. All rights reserved.

Five reversibly thermochromic bismuth-based inorganic–organic hybrid materials were synthesized via facile one-step condensation reactions between triphenylbismuth and four arenedithiols and a diselenol. The materials were characterized by UV-vis and FT-IR spectroscopy, powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), elemental analysis (EA), and thermogravimetric analysis (TGA). The bismuth-organic materials (Bi-OMs) are colored materials with optical HOMO–LUMO gaps that were readily tuned by systematic modification of the steric and electronic character of the π-conjugated organic linkers. All five Bi-OMs exhibit completely reversible thermochromism in the solid-state, and possess excellent thermal stability in air up to nearly 300 °C. This combination of physical properties, coupled with the ease of synthesis and the inexpensive, non-toxic nature of bismuth, make this class of inorganic–organic hybrid materials potentially promising for reversible smart window applications, camouflage coatings, temperature sensing, photocatalysis, color filters and displays.

The highly efficient base-catalyzed thiol-epoxy reactions were exploited in dispersion polymerizations as a simple method for the preparation of uniform and cross-linked particles with a tunable size, glass transition temperature (Tg) and network structure. Particles with sizes ranging from 1 μm to 3 μm could be obtained by varying monomer concentration and reaction medium, while the Tgs could be increased from −10 °C to 65 °C by adjusting the monomer functionality and structure. In order to further demonstrate the potential of these particles, the thioether bonds were simply oxidized to sulfoxides and sulfones to increase the Tgs and stiffness of the particles significantly. Moreover, the cross-linked particles proved to be reprocessable to a polymer material when a proper catalyst was incorporated. We believe that this simple and efficient method will become a powerful tool for particle preparation, and paves the way for polymer particle reinforcement and recycling.

To enhance the utilization of visible light and prevent photogenerated electrons/holes from recombination, black TiO2 hollow spheres of varying shell thicknesses rich in Ti3+ were synthesized via hydrogenation with the aid of Pd. With increasing hydrogenation temperature from room temperature to 200 °C, the thickness of the disordered layer increases, and the concentration of Ti3+, which is the main active site for photocatalysis, also increases. Owing to the intense visible-light harvesting nature and rich active sites introduced by the disordered layer, the black TiO2 hollow spheres obtained at 200 °C degrade rhodamine B (RhB) to 95.2% within 120 min under visible-light illumination. In addition to the role of enhanced visible-light absorbance, Ti3+ also improves the conductivity, which is further confirmed with Li-ion batteries. The enhanced conductivity favors the separation of photogenerated electrons/holes.

OH radical is the most important oxidant in the atmosphere, and controls the tropospheric concentration of tropospheric trace gases such as CO, SO2, NO2, CH4 and other volatile organic compounds. Accurate measurement of the concentration of OH radical in troposphere is the key to clarifying the formation mechanism of secondary pollution in China. The laser-induced fluorescence (LIF) technique is widely used in tropospheric OH radical field observation due to its high sensitivity, high selectivity, and small interference. However, the LIF technique is not an absolute measurement technology. In recent years, OH radical measurements and simulations in many field observations show that the improvement of accuracy of calibration is a way to reduce the differences. Currently, the common calibration methods are ozone-alkene method and water photolysis method. Further improving the accuracy of calibration is a key factor to ensure the accurate measurement of OH radicals. In this paper, a portable calibration method of OH radicals based on simultaneous photolysis is introduced. The synthetic air with a certain water vapor concentration is irradiated in laminar flow by 185 nm light of mercury lamp, and the photolysis of water vapor and O2 produce OH, HO2 radicals and O3. The concentration of OH radicals is calculated by oxygen concentration, water vapor concentration, ozone concentration, oxygen absorption cross section and water vapor absorption cross section. The water vapor is measured by a high-precision temperature and humidity probe, and the systematic error of the probe is corrected by 911-0016 ammonia (NH3, H2O) analyzer. As the ozone concentration is only 0.5－1 ppb in the calibration, the commercial ozone analyzer cannot meet the requirement for the measurement. A high-precision ozone analyzer O3-CRDS based on cavity-ring-down spectrocopy is built to achieve the detection limit of 15 ppt (1σ). Using the O3-CRDS analyzer, the concentration distribution coefficient of ozone in laminar flow along the radial direction of the flow tube (P = 1.9) is measured. Because the absorption cross section of oxygen at 185 nm is seriously affected by oxygen column concentration and the characteristics of mercury lamp, the oxygen absorption cross section is remeasured based on Lambert’s law, which is \begin{document}$ \sigma_{\rm O_2} $\end{document} = (1.25 ± 0.08)×10–20 cm2. The portable calibration device is established by establishing the corresponding relationship between ozone concentration and light intensity. By changing the concentration of water vapor in the flow tube, the OH radicals with concentrations in a range of 3×108－2.8×109 cm–3 are produced, which are used to calibrate the atmospheric OH radical measurement instrument based on LIF technique. The fluorescence signal has a good correlation with the concentration of OH. The calibration device of OH radical is used to calibrate the LIF system during “a comprehensive study of the ozone formation mechanism in Shenzhen” (STORM) field observation in Autumn 2018. The calibration results under the field condition show that the calibration uncertainty of the calibration device for LIF instrument is 13.0%, which has good stability and accuracy.

The micropumps with the novel saw-tooth microchannels and the traditional diffuser microchannels have been fabricated. The PDMS-glass-silicon-PDMS structure of the micropumps look like a sandwitch. The pump body based on the silicon wafer has been produced through the advanced microfabrcation technique. The sealing between the silicon and the glass wafer by anodic bonding technology has been carried out, the irreversible sealing between the PDMS and glass, the silicon and PDMS by UV irradiation have been adopted. Finally, the maxmium pressure head (MPH) and the maximum flow rate (MFR) of the two micropumps have been tested with different driving voltages and frequencies under sine, square and ramp signals. The results show that the MPH and MFR value increased along with the driving voltage under some frequency, and the effects of the sine wave driving are prior to other waves. The performance of the micropump with the novel saw-tooth microchanels has been enhanced greatly compared to the traditional diffuser micropump. Through experimental results measured the maximum value of MFR and MPH at two specific frequencies by driving micropump with 100V p-p are 63.6µl/min at 200 Hz and 1328.8 Pa at 200Hz for the saw-tooth micropump under the sine signal driving, and 45.1µl/min at 60 Hz and 681Pa at 60 Hz for the traditional diffuser micropump under the square signal driving.