Urea-formaldehyde resin room temperature phosphorescent material with ultra-long afterglow and adjustable phosphorescence performance.

Organic room-temperature phosphorescence materials have attracted extensive attention, but their development is limited by the stability and processibility. Herein, based on the on-line derivatization strategy, we report the urea-formaldehyde room-temperature phosphorescence materials which are constructed by polycondensation of aromatic diamines with urea and formaldehyde. Excitingly, urea-formaldehyde room-temperature phosphorescence materials achieve phosphor lifetime up to 3326 ms. There may be two ways to enhance phosphorescence performance, one is that the polycondensation of aromatic diamine with urea and formaldehyde promotes spin-orbit coupling, and another is that the imidazole derivatives derived from the condensation of aromatic o-diamine with formaldehyde maintains low levels of energy level difference and spin-orbit coupling, thus achieving ultra-long afterglow. Surprisingly, urea-formaldehyde room-temperature phosphorescence materials exhibit tunable phosphorescence emission in electrostatic field. Accordingly, 1,4-phenylenediamine, urea, and formaldehyde are copolymerized and self-assembled into phosphorescence microspheres with different electrostatic potential strengths. By mixing 1 wt% 1,4-phenylenediamine polycondensation microspheres with 1,4-phenylenediamine free microspheres, phosphor lifetime of the composite could be regulated from 27 ms to 123 ms. Moreover, vulcanization process enables precise shaping of urea-formaldehyde room-temperature phosphorescence materials. This work not only demonstrates that urea-formaldehyde room-temperature phosphorescence materials are promising candidates for organic phosphors, but also exhibits the phenomenon of electrostatically regulated phosphorescence.

Hydroxy-Rich Covalent Organic Framework for the Efficient Catalysis of the Cycloaddition of CO2.

The cycloaddition of CO2 with epoxides to cyclic carbonates is one of the most promising and green pathways for CO2 utilization, and the development of highly efficient catalysts remains a challenge. In this work, a novel hydroxy-rich covalent organic framework (TFPB-DHBD-COF) was synthesized, and it served as an efficient heterogeneous catalyst for the reaction of CO2 with 1,2-epoxybutane under mild conditions, providing the desired products in 90% conversion. The abundant hydroxy groups in the pore channels of TFPB-DHBD-COF could not only activate epoxides and CO2 via hydrogen bonding but also obviously enhance its stability through intramolecular five-membered ring hydrogen bonding. Thus, this COF also exhibited outstanding stability and tolerance for diverse substrates. Undoubtedly, this work has enriched the application of tailored COFs in the activation and utilization of CO2.

Construction of room temperature phosphorescent materials with ultralong lifetime by in-situ derivation strategy.

Although room temperature phosphorescence (RTP) materials have been widely investigated, it is still a great challenge to improve the performance of RTP materials by promoting triplet exciton generation and stabilization. In this study, an in-situ derivation strategy was proposed to construct efficient RTP materials by in-situ deriving guest molecules and forming a rigid matrix during co-pyrolysis of guest molecules and urea. Characterizations and theoretical calculations revealed that the generated derivatives were beneficial for promoting intersystem crossing (ISC) to produce more triplet excitons, while rigid matrix could effectively suppress the non-radiative transition of triplet excitons. Thus, the in-situ derivation strategy was concluded to simultaneously promote the generation and stabilization of triplet excitons. With this method, the ultralong lifetime of RTP materials could reach up to 5.33 s and polychromatic RTP materials were easily achieved. Moreover, the potential applications of the RTP materials in reprocessing or editable anti-counterfeiting were successfully demonstrated.

Continuous synthesis of 2,2,6,6-tetramethyl-4-piperidinol over CuCrSr/Al2O3: effect of Sr promoter.

A continuous process was developed for catalytic hydrogenation of triacetoneamine (TAA) to 2,2,6,6-tetramethyl-4-piperidinol (TMP), both of which are indispensable raw materials of hindered amine light stabilizers. A series of promoter-modified CuCr/Al2O3 catalysts were prepared by co-precipitation method and evaluated by the above reaction. The effect of promoter on the catalytic performance was explored by characterization tools, in which, CuCrSr/Al2O3 exhibited excellent catalytic performance with nearly complete conversion of TAA and over 97% selectivity of TMP at 120 °C. The characterization results indicated that the doped Sr could decrease the size of Cu nanoparticles to provide more active sites, improve the ratio of Cu+/Cu0 to promote the adsorption of substrates, and reduce the surface acidity to depress side reactions, thus remarkably enhancing catalytic performance. This work provides a low-cost, reliable and efficient strategy for the continuous industrial production of TMP.

Lipid Droplet-Specific Dual-Response Fluorescent Probe for the Detection of Polarity and H2O2 and Its Application in Living Cells.

H2O2 and polarity are quite important in many physiological and pathological processes, and their relationship is complicated and obscure for researchers. Thus, it is vital and challenging to achieve simultaneous detection of H2O2 and polarity in vivo. Herein, the first naphthalimide-triphenylamine-based dual-site fluorescent probe NATPA is developed for simultaneously imaging intracellular H2O2 and polarity fluctuations. It exhibits excellent sensitivity (LOD = 44 nM), selectivity, and fast response (15 min) to H2O2 and a superior capacity for detecting polarity upon the intramolecular charge transfer (ICT) effect. Besides, the probe displays low cytotoxicity and lipid droplet targeting and is further applied in imaging H2O2 and polarity fluctuations in HepG2 and L-02 cells, so that NATPA is qualified to distinguish cancer cells from normal cells. This research contributes a new design principle for the construction of dual-site fluorescent probes for simultaneously detecting active molecules and polarity.

Photoinduced charge-separated molecular probe for ultrasensitive spectrum analysis and rapid colorimetric detection of platinum ions.

Increased utilization of platinum ions in chemicals and drugs escalates environmental pollution and toxicity associated with Pt ions. However, current analysis and detection strategies of Pt ions display limited sensitivity due to the similar inert metal nature of platinum to gold. Herein, a photoinduced charge-separated molecule (MTPA)2Ab was synthesized as a probe for enhanced sensitive selection of Pt ions. Long-lived charge-separated states generated upon exposure to 365 nm light lead to a stable complex between (MTPA)2Ab and PtCl2/PtCl4 with highly-selectivity via sequential photoinduced electron transfers. Owing to the linear relationship of complex characteristic absorption and fluorescence emission intensities to Pt2+/Pt4+ concentrations, ultrasensitive spectrum analysis of Pt ions is achieved with a detection limit of 14.2 nM (2.8 ppb) for Pt2+ and 12.6 nM (2.5 ppb) for Pt4+ by an absorption spectrometer and 9.8 nM (1.9 ppb) for Pt ions (Pt2+/Pt4+) by a fluorescence spectrometer, far less than the reported values. Furthermore, a portable test box is developed based on (MTPA)2Ab test strips due to distinguishable color change with Pt2+/Pt4+ concentrations for rapid colorimetric detection of Pt ions. The results highlight the promise of photoinduced charge-separated molecular probe in ultrasensitive and rapid detection of Pt ions to overcome current limitations of detection strategies.

Dual-site fluorescent probe for multi-response detection of ClO- and H2O2 and bio-imaging.

Hypochlorite (ClO-) and hydrogen peroxide (H2O2) commonly coexist in organism and are involved in the same physiological and pathological processes. So it is of great importance to develop fluorescent probes to detect both simultaneously. Herein, we reported the first dual-site fluorescent probe (Geisha-1) for the quantitative detection of ClO- and H2O2. This probe is constructed by chemically grafting N,N-dimethylthiocarbamate and borate to a fluorescence resonance energy transfer (FRET) platform. As a result, Geisha-1 not only presents three different responses to ClO-, H2O2, and ClO- + H2O2 (the coexistence of ClO- and H2O2) with high sensitivity and selectivity, but also exhibits low toxicity and cell membrane and tissue permeability, and it was further successfully applied to image ClO- and H2O2 in living cells and tissues. Thus, Geisha-1 provides a promising application prospect in biological systems and an alternative strategy for the construction of dual-site fluorescent probes aiming at the multi-response detection of other biologically relevant analytes.

Biomass-derived Fe-NC hybrid for hydrogenation with formic acid: control of Fe-based nanoparticle distribution.

A series of Fe-NC catalysts were synthesized by pyrolyzing an Fe complex and wheat flour at 500 °C. All of them were characterized and applied in the catalytic transfer hydrogenation of nitroarenes with formic acid. It was found that the catalytic activity was significantly affected by the size and distribution of Fe-based nanoparticles (NPs), which could be easily regulated by altering the Fe source. Meanwhile, more basic nitrogen sites were preserved on the catalyst so that the reaction ran smoothly without base additives. Among all catalysts, Fe-NC-FeCl2 exhibited the best catalytic performance due to smaller Fe3O4 NPs and greater N doping. Moreover, it showed excellent applicability for diverse nitroarenes. Obviously, this work demonstrates the importance of the metallic NPs' size and distribution, providing a new insight into the design of M-NC catalysts. The catalyst is economical and eco-friendly, and shows potential application value in industry.

Design, synthesis, immunocytochemistry evaluation, and molecular docking investigation of several 4-aminopyridine derivatives as potential neuroprotective agents for treating Parkinson's disease.

Neuroprotection refers to the relative preservation of neuronal structure and function. Neuroprotective agents refer to substances that are capable of preserving brain function and structure. Currently, there are no neuroprotective agents available that can effectively relieve the progression of Parkinson's disease. In this work, five novel 4-aminopyridine derivatives, including three amides and two ureas, were designed, synthesized, and evaluated using the rat PC12 mice pheochromocytoma cell line as an in vitro model. As well as human Rho kinase inhibitory experiment was performed. Among them, compound 3, which exhibited high cell viability, low cytotoxicity and good efficacy of inhibition on α-synuclein, oxidation, inflammation and Rho kinase, was profound as potential agents for Parkinson's disease (PD).

Two-Dimensional Imine-Linked Covalent Organic Frameworks as a Platform for Selective Oxidation of Olefins.

Two-dimensional imine-linked covalent organic frameworks with hydroxyl groups, TAPT-DHTA-COFHX and TAPT-DHTA-COFDMF, were respectively constructed by the condensation of 1,3,5-tris-(4-aminophenyl)triazine and 2,5-dihydroxyl-terephthalaldehyde under solvothermal and reflux conditions. Both COFs possess excellent thermal stability and a similar eclipsed stacking structure verified by XRD patterns. However, TAPT-DHTA-COFHX presented a larger surface area (2238 m2/g) and higher crystallinity than TAPT-DHTA-COFDMF. Significantly, copper ions are efficiently incorporated into the pores of these two COFs via the coordination interaction with hydroxyl groups and imine linkers. The obtained copper-containing COFs (Cu-COFHX and Cu-COFDMF) were employed in the selective oxidation of styrene to benzaldehyde. Cu-COFHX with superior surface area (1886 m2/g) and pore volume (1.11 cm3/g) exhibited excellent catalytic performance and recyclability. This strategy not only provides a convenient approach to design imine-linked 2D COFs with hydroxyl groups, but also develops their novel application for catalysis.

A near-infrared multifunctional fluorescent probe with an inherent tumor-targeting property for bioimaging.

A mitochondria-targeting probe, by conjugating a quaternary ammonium cation with glucosamine modified pH-activated cyanine, was designed and synthesized. This probe has excellent selectivity and sensitivity toward pH, stability, cellular membrane permeability and low cytotoxicity. Owing to the acidic feature of tumors and the more negative mitochondrial membrane potential of tumor cells than that of normal cells, this probe can selectively accumulate in tumor cells and light up its fluorescence. It has been successfully applied for in vivo tumor imaging with a high signal-to-noise ratio. Moreover, this multifunctional switchable sensor was also employed for the fluorescent imaging of the fluctuation of intracellular pH in HeLa cells.

A sensitive colorimetric and ratiometric chemosensor for trivalent metal cations.

A novel hydroxyethyl piperazine functionalized cyanine derivative was designed and synthesized. It presents selective colorimetric as well as ratiometric absorption responses to trivalent metal cations (Cr(3+), Fe(3+) and Al(3+)) over a variety of divalent and monovalent metal cations in 3:7 ethanol-water solution. Detection limits of this method for Cr(3+), Fe(3+) and Al(3+) were 3.99 µM, 4.30 µM and 1.85 µM, respectively. The recognition mechanism was attributed to the protonation of the organic probe, which blocked the photoinduced electron transfer (PET) process. In addition, the sensor was also successfully applied to the determination of Cr(3+) in prepared samples.

Regulating the piezofluorochromism of 9,10-bis(butoxystyryl)anthracenes by isomerization of butyl groups.

Isomers of 9,10-bis(butoxystyryl)anthracene (DSA4), including n-butyl, i-butyl and t-butyl at ortho or para positions, were designed and synthesized. All of them display an aggregation-induced emission phenomenon. Remarkably, it was found that isomerization of butyl endgroups presents significant influences on their piezofluorochromic properties. Thus, an alternative approach to design and obtain piezofluorochromic compounds is proposed here.

Spectrofluorimetric determination of trace nitrite with a novel fluorescent probe.

A simple, sensitive and selective fluorimetric determination for trace nitrites was developed using an unsymmetrical rhodamine with a high fluorescence quantum yield and large Stokes shift. The method is based on the reaction of the unsymmetrical rhodamine with nitrite in an acidic medium to form a nitroso product, which has much lower fluorescence because the electron-withdrawing effect of the nitroso group influences the system of p-pi conjugation between N atom and benzene ring. Under optimum conditions, the fluorescence quenching intensity is linear over a nitrite concentration range of 1.0 x 10(-8) to 3.5 x 10(-7)M. The detection limit is 2.0 x 10(-10)M (S/N=3). The method was applied to the determination of nitrite in tap water and lake water with satisfactory results. The mechanism for the reaction is also reported.

(S)-1-Hydroxy-propan-2-aminium (2R,3R)-3-carb-oxy-2,3-dihydroxy-propanoate monohydrate.

The chiral title compound, C(4)H(10)NO(+)·C(4)H(5)O(6) (-)·H(2)O, is a hydrated mol-ecular salt in which the tartaric acid has transferred one proton to the (S)-2-amino-propan-1-ol mol-ecule. The crystal structure is stabilized by a three-dimensional network of N-H⋯O and O-H⋯O hydrogen bonds. The absolute configuration was assigned on the basis of the starting materials.

New fluorescent labels: 4- and 7-chlorofluorescein.

A new mixture of 4- and 7-chlorofluorescein were synthesized by condensation of resorcinol with 3-chlorophthalic anhydride in the presence of methanesulfonic acid or zinc chloride. These regioisomers were successfully separated by chromatography. The photophysical properties were examined and their absorption and emission maxima at long wavelength, high fluorescence quantum yield, and narrow emission bandwidth were found, highly favorable for detecting multiple target substances in the same sample. Furthermore, 4(7)-chlorofluorescein was found to be strongly pH-dependent between 4.0 and 8.0, and could be used as pH-sensitive fluorescent probe to measure intracellular pH.

Packing structure and self-heating in capillary electrochromatography.

The origin of bubble formation during operation of capillary electrochromatography (CEC) has been an issue of debate. Ohmic heating resulted from current passed through a packed column was proposed as the primary cause. However, this explanation has been questioned on the ground that the current measured in CEC is much lower than that measured with open-tubular separation systems where no bubble formation occurs. To resolve this issue, we carried out a theoretical study correlating self-heating of the electrolyte with packing structure of the column. We used a bundle of capillary tubes, a bundle of two types of capillary tubes and two bundles of capillary tubes connected serially to model, respectively, the flow channels in the column of non-porous particles, in the column of porous particles and in the column of various packing densities. The results from this study indicate that, for columns of homogeneous packing density, the heat output is indeed smaller than that in open-tubular columns of the same dimensions. In this case, the self-heating cannot be a key factor responsible for the bubble formation in CEC. However, for columns of heterogeneous packing density, a large excess of heat release may be produced in column sections of high packing density and, in turn, over-heating in such sections may become the primary cause for the formation of bubbles. It follows from this study that preparation of columns of homogeneous packing structure is essential to obtain reproducible and bubble-free CEC systems.

Measurement of packing tortuosity and porosity in capillary electrochromatography.

The application of conductivity measurements for packing structure characterization has been extended to a column consisting of a packed section and an open section as typically used in capillary electrochromatography (CEC). Because of the difference in electric conductivity between the packed and open sections, the electric fields applied across the two sections vary, depending on the length of the packed section relative to that of the total column. On the basis of mass conservation law, it can be shown that the ratio of the electric current measured in such a duplex column to that without packing is a function of the length and the geometric structure of the packing bed. Thus, knowing the lengths of the packed section and the whole column, we can readily calculate the obstructive factors, such as the porosity and the tortuosity factor, from the measured conductivity ratio. An example is given to demonstrate the application of this method, with experimental data taken from published work.