查看更多>>摘要：Thermally activated delayed fluorescence(TADF)materials with through-space charge transfer(TSCT)have recently attracted extensive attention.However,how to rationally design high-performance TSCT-TADF emitters with small ΔE_(ST),high photoluminescence quantum yields(PLQYs)and high stability remains challenging.Herein,two triptycene-derived TADF molecules bearing ortho-donor(D)-acceptor(A)conformations are designed and characterized.These emitters exhibit unique V-shaped face-to-face D-A alignments with significant intramolecular D-A interactions,which mediate TSCT between the D and A moieties in addition to the through-bond charge transfer(TBCT)and facilitate realizing small ΔE_(ST)and high efficiencies.Meanwhile,the rigid 3D triptycene scaffold endows the emitters with excellent thermal stability and high film-formation quality.These TADF emitters exhibit small ΔE_(ST)of 6.7 and 10.8 meV and high photoluminescence quantum yields of 0.80 and 0.40 in doped films,respectively.The doped OLEDs employing these emitters achieve high external quantum efficiencies up to 20.5%.
查看更多>>摘要：Nowadays,design of conventional and efficient optical H2O2 sensors would be of great importance due to their lower cost and ease of follow-up,compared to the other widely used techniques such as electrochemical or chromatographic methods.Here,stimuli-responsive sensors containing photochromic(R/S)-2-(3',3'-dimethyl-6-nitro-3'H-spiro[chromene-2,2'-indole]-1'-yl)ethanol(SPOH)and acrylic terpolymer film or nanofibers were prepared for H2O2 detection through a reaction-induced and concentration-dependent process.The polymer phase acts as an efficient substrate for exploitation of such sensors in aqueous media.Poly(methyl methacrylate-butyl acrylate-hydroxyethyl methacrylate)(MBH)was prepared via miniemulsion polymerization and its chemical structure was characterized by FTIR and ~1H NMR spectroscopies.Then,it was doped with SPOH and the corresponding film(MBH/SPOH@F)and nanofibers(MBH/SPOH@NF)were fabricated via spin-coating and electrospinning techniques,respectively,and their morphologies were investigated by SEM.Golorimetric analyses were employed to evaluate performance of the obtained samples toward H2O2 after sensitization by UV irradiation.Both samples demonstrated visual color changes together with decrement in maximum absorption wavelengths with the increase in H2O2 concentration.Limit of detection(LOD)for MBH/SPOH@F and MBH/SPOH@NF were calculated to be 11 and 2.3 mg/dL,respectively.Moreover,MBH/SPOH@NF showed faster response(50 min)with respect to MBH/SPOH@F(60 min).Enhanced sensitivity of MBH/SPOH@NF comes from higher specific surface area and porosity of the nanofibers compared to the corresponding film.This led to more accessibility of H2O2 to SPOH molecules in the detection process.Finally,practical application of the ready-to-used and solid sensor was validated with the recovery of 94-97% in water resources.
查看更多>>摘要：Recently,the research of organic room-temperature phosphorescent materials(ORTP)and organic long persis-tent luminescence(OLPL)has become a hot topic in the fields of chemistry and material science.To date,there are many reports on the realization of high-efficiency ORTP and OLPL by doping system of organic small mol-ecules,which have attracted widespread attention due to their unique luminescence performance.However,given the lack of clear molecular design principles and comprehension in elucidating the complex doping mechanisms,the development of ORTP and OLPL by doping system is strongly limited,as well as further practical application.A variety of activation strategies including rigidification,energy transfer,charge transfer(GT)intermediated state and cluster have been developed in the reported doping system.Moreover,OLPL ma-terials were also developed with impressive luminescent lifetime.This mini-review summarizes the recent research progress of ORTP and OLPL by doping system of organic small molecules.The reported doping systems of the organic molecules are mainly categoried according to the different luminescent mechanisms,combined with the discussion on the relationship between molecular structure and luminescent performance.This would be helpful to understand luminescent characteristics deeply and further develop efficient ORTP and OLPL doping systems.Last but not the least,this review presents the current challenges and prospects of future development in this field.
查看更多>>摘要：The crosslinking of glutaraldehyde(GA)and nano-selenium coated chitosan(CS-SeNPs)afforded composites(GA-CS-SeNPs)which exhibit new properties.In addition to having mimic enzyme activity of CS-SeNPs,these composites exhibit fluorescence,which CS-SeNPs did not possess.The GA-CS-SeNPs can catalyze the chromo-genie process of oxidation of substrate TMB at 20 ℃ and pH of 3.5,and under the excitation wavelength of 440 nm,the composites can emit strong fluorescence.The presence of mercury(II)(Hg~(2+))inhibited the color process of catalytic oxidation of 3,3,5,5,-tetramethylbenzidine(TMB)and enhanced the fluorescence intensity of the composites to some extent.Therefore,using the fluorescence and mimicking enzyme properties of GA-CS-SeNPs,a fluorescent and colorimetric(dual-mode)determination of Hg~(2+)was developed with good selectivity and high sensitivity.The linear determination ranges of Hg~(2+)were 0-55 μM and 0-50 ^M for fluorescent and colorimetric assays,respectively,and the limits of detection(LOD)for the dual-mode assay were as low as 0.34(iM and 0.40 μM,respectively.In addition,this new method was successfully implemented for dual-mode determination of Hg~(2+)in real samples.
查看更多>>摘要：Aggregation-induced emission(AIE)fluorescent molecules are in great demand due to the wide range of applications.In this article,three regioisomers namely,o-PyPTZ,m-PyPTZ and p-PyPTZ,with pyrazine(Py)as acceptor and phenothiazine(PTZ)as donor,were rationally designed and synthesized.Phenothiazine moieties are attached to pyrazine core as peripheral groups at 2,3-2,5-and 2,6-positions.The attachment of bulky PTZ pendants at different position of pyrazine core could influence the molecular packing modes,resulting in discrete photophysical and electronic properties.The resulting regioisomers are weakly fluorescent in dilute solutions but highly emissive upon aggregate formation,verifying their AIE activities.They are thermally and morphologically stable with degradation temperature of 372-407 ℃.Single-crystal structures of three isomers indicate their twisted conformation.A detailed comparison of the photophysical,electronic and structural properties of these isomers has been made with a view to studying the outcome of the positional change.
查看更多>>摘要：A coumarin hydrazone ligand 1 not only displays a dual-state emission but also has an ability to behave as a solid-state fluorescent sensor for vapor detection of volatile acid and ammonia(1 = 7-(diethylamino)-2-oxo-N'-(pyridin-2-ylmethylene)-2H-chromene-3-carbohydrazide).The mechanism of"OFF"fluorescent signal of conjugate acid of 1(H1~+)is due to the formation of H-aggregate with aggregation-caused quenching(ACQ)effect,however,molecule stacking of protonated counterpart H1~+-C1O4-DCE with staircase arrangement of J-aggregates exhibited an orange emission in the solid state,acting as crystallization-induced emission(CIE)active nature.Moreover,the color and fluorescence emission of CIE-active molecule can be switched by external stimuli including grinding and solvent vapor.Utilizing the excellent OFF-ON response to HCl-NH3 vapor in the solid state,H1~+ acts as a colorimetric and fluorometric dual-channel indicator upon exposure to total basic volatile nitrogen(TVB-N)compounds from fish as it spoils.The freshness of different batches,species and temperatures of fillets were readily monitored using standard chemometric and fluorometric approaches,providing in situ quality assurance(QA)information for fisheries industries and consumers.
查看更多>>摘要：In this paper,a lophine-based phenol compound has been prepared and identified as an efficient chromophore for the determination of hydrogen peroxide(H2O2)with enzymatic method.A dry chemistry analytic agent was also prepared involving this compound,showing good accuracy in the determination of uric acid.However,a commonly used solvent dichloromethane(DCM)could react with this imidazole derivative when the reaction mixture was irradiated under UV(365 nm).We explored the possible mechanism and identified several byproducts caused by the acidity and ultraviolet oxidation of DCM.Caution should be taken in the synthesis and application of such imidazole-based dyes in DCM,especially when phenol group was introduced to the imidazole moiety.
查看更多>>摘要：The combination of excellent luminescence with high solvent polarity effect and aggregation induced emission(AIE)is an ideal combination for creating fluorophores/probes with high microenvironmental sensitivity.However,many push-pull chromophores of the D-A type in common intramolecular charge transfer(ICT)state with a significant solvatochromic effect and AIE activity,have poor luminescent properties.Herein,to overcome this problem by using reactions of nucleophilic aromatic hydrogen substitution(S_N~H),we have designed a series of novel 4-heteroaryl-substituted 2-aryl-2H-benzo[4,5]imidazo[1,2-a] [ 1,2,3] triazolo[4,5-e] pyrimidine fluorophores possessing a planarized intramolecular charge transfer(PLICT)state.All these fluorophores exhibited high luminescence quantum yields(up to 60%)and large Stokes shift values of up to 7459 cm~(-1).Among them,the fluorophore 4h was found to exhibit the most pronounced positive solvatochromic effect and the probe 4f exhibited the most pronounced aggregation induced emission characteristics.This AIE behavior was further confirmed by means of time-resolved fluorescence lifetime measurements as well as DFT-assisted geometry optimization studies.In the presence of trifluoroacetic acid(TFA)compound 4h exhibited a well-pronounced acidochromism via visible color change from yellow-green to orange which returned to the original yellow-green solution after the addition of triethylamine(TEA).The Stern-Volmer constant for the probe 4h towards TFA was 38 M~(-1).Finally,for the compounds 4f,g,h theoretical calculations in the ground and excited states in different solvents were carried out to confirm the PLICT process.Based on all above the herein reported PLICT fluorophores 4a-h can be successfully applied as biological probes and optical switches.
查看更多>>摘要：Electrospun polydiacetylenes(PDAs)composite materials are favorable for practical applications.However,a further understanding of the colorimetric changes of the composite systems in terms of thermodynamic and metastable states resulting from the interactions among multiple components is normally neglected.Herein,we functionalized diacetylenes with a variety of head groups and used them to prepare electrospun films with polyethylene oxide(PEO)as the matrix.Detailed investigations have been performed on the thermochromic properties of the PDA/PEO composite films to profile their general energy landscapes that describe the identified metastable and thermodynamic colorimetric states.Underlying mechanisms for the generation of multiple energy minima were proposed on the basis of chemical structures of PDA head groups.Utilizing the fmed-tuned chromic responsiveness of the PDA/PEO composite films under thermo-and pH stimulations,as well as the features of thermodynamic and metastable states,we fabricated delicate devices for secret codes with multiple deciphering pathways and temperature sensors with a high-temperature recording function.
查看更多>>摘要：This work presents a theoretical study on a series of full-color-tunable wavelength carbohelicene dyes to understand what controls the color of fluorescence and quantum efficiency at the quantum level.The tunable wavelength of the experimental spectra and substituent effect on the spectral properties have been reproduced and analyzed.The results show that the introduction of NMes2 and(or BMe2)enlarges the conjugated length,stabilizes the LUMO and lowers the HOMO-LUMO gap which finally tunes the spectral wavelength.Though the pure electronic calculations reproduce well the relative position of different spectra,vibronic effect is further considered to make up the limitation of pure electronic spectra in reproducing the experimental fine structures.To further reveal the features of excited states,the radiative rate(kr)and non-radiative rates(k_(IC)and k_(ISC))are computed to predict the quantum yield(QY).The calculated QY agree well with experimental ones.The results show that the introduction of BMes2(7B-HC)increases kr and reduces k_(ISC)which finally leads to the increase of QY.We also show that the competition between kr and k_(ISC)is the dominant reason for the quenched QY of molecule 7B-HC by 35%.The large SOC and small energy gap between S1 and the lowest six triplet excited states are highlighted for the highly accelerated ISC processes.The nice agreement with the experiment indicates that the QY calculation method can be provided as an efficient approach for the prediction of promising fluorescent dyes.
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