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1.
本工作以葡萄糖为碳源,乙二胺、浓磷酸为氮、磷杂原子供体,通过酸碱中和自放热法制备氮磷共掺杂碳量子点(N,P-CDs)。基于柠檬黄对N,P-CDs荧光的猝灭效应,构建了一种快速灵敏检测柠檬黄的荧光方法。在最佳实验条件下,N,P-CDs对柠檬黄的检测展现出高选择性和高灵敏度特点,柠檬黄浓度在0.01-10.0μM范围内与N,P-CDs荧光猝灭效率呈良好线性关系,检测限低至11.6 nM。最后,本工作将该方法用于食品样品中柠檬黄的检测,加标回收率在96.1%~104.9%范围内,相对标准偏差(RSDs)低于3.3%,结果令人满意。  相似文献   
2.
We present a new full-dimensional diabatic potential energy matrix (DPEM) for electronically nonadiabatic collisions of OH(A 2Σ+) with H2, and we calculate the probabilities of electronically adiabatic inelastic collisions, nonreactive quenching, and reactive quenching to form H2O+H. The DPEM was fitted using a many-body expansion with permutationally invariant polynomials in bond-order functions to represent the many-body part. The dynamics calculations were carried out with the fewest-switches with time uncertainty and stochastic decoherence (FSTU/SD) semiclassical trajectory method. We present results both for head-on collisions (impact parameter b equal to zero) and for a full range of impact parameters. The results are compared to experiment and to earlier FSTU/SD and quantum dynamics calculations with a previously published DPEM. The various theoretical results all agree that nonreactive quenching dominates reactive quenching, but there are quantitative differences between the two DPEMs and between the b=0 results and the all-b results, especially for the probability of reactive quenching.  相似文献   
3.
Molecular self‐assembly is a powerful means to construct nanoscale materials with advanced photophysical properties. Although the protection of the photo‐excited states from oxygen quenching is a critical issue, it still has been in an early phase of development. In this work, we demonstrate that a simple and typical molecular design for aqueous supramolecular assembly, modification of the chromophoric unit with hydrophilic oligo(ethylene glycol) chains and hydrophobic alkyl chains, is effective to avoid oxygen quenching of triplet–triplet annihilation‐based photon upconversion (TTA‐UC). While a TTA‐UC emission is completely quenched when the donor and acceptor are molecularly dispersed in chloroform, their aqueous co‐assemblies exhibit a clear upconverted emission in air‐saturated water even under extremely low chromophore concentrations down to 40 μm . The generalization of this nano‐encapsulation approach offers new functions and applications using oxygen‐sensitive species for supramolecular chemistry.  相似文献   
4.
A novel water-soluble luminescent complex consisting of Eu(ally-dbm)\begin{document}$_3$\end{document}-2Tppo and poly(N-isopropyl acrylamide) (PNIPAM) is synthesized through a series of chemical reactions. The structure of the complex is characterized by TGA, GPC, HNMR, and the thermal-responsive fluorescence of the complex in aqueous solution is investigated. It is found that PNIPAM collapse above the lower critical solution temperature causes the coordination bond breaking, leading to weakening of the fluorescence from Eu\begin{document}$^{3+}$\end{document} and enhancing of the fluorescence from the ligands. When temperature decreases, the fluorescence from Eu\begin{document}$^{3+}$\end{document} is found to boost up and the fluorescence from ligands weakens accordingly. It is deduced from this phenomenon that the ligands re-coordinate with europium ions again along with the temperature decreasing, which is further confirmed by IR measurements. This thermal-responsive fluorescence is of reversibility, which can be used as molecular probes for biological imaging and collapse studying of PNIPAM.  相似文献   
5.
The fluorescence quenching of Rhodamine 6G (R6G) by graphene oxide (GO) was interrogated by R6G fluorescence measurements using a set of controlled GO samples with varied C/O ratios as the quencher.The carbonyl groups on the GO nanosheet turned to play a dominant role in quenching the R6G fluorescence.The quenching in the static regime can be described by the "sphere of action" model.The significant absorption of the R6G fluorescence by the ground-state complex formed between R6G and GO was identified to be responsible for the static quenching.This work offers helpful insights into the fluorescence quenching mechanisms in the R6G/GO system.  相似文献   
6.
以柠檬酸为碳源,三聚氰胺和甲醛为双掺杂剂合成碳量子点,并对合成的量子点进行透射电镜(TEM)、傅里叶变换红外光谱(FTIR)、X射线粉末衍射(XRD)、紫外吸收光谱(UV)和荧光光谱(RF)表征,结果表明该量子点粒径均一,发光稳定,适合用作荧光探针。优化了碳量子点含量、pH、反应时间以及温度等影响因素,结果显示检测波长λmax=425 nm时,连翘苷在0.008~0.030 mg/mL范围内有良好的线性关系,1/△f=0.00005(1/c)+0.0003(R2=0.9948),加标回收率在92.5%~106.3%之间,RSD<5%,且干扰物质、反应时间、温度等因素在一定范围内对实验结果的测定无影响。该方法可用于药剂中连翘苷含量的测定。  相似文献   
7.
Device grade quantum dots (QDs) require QDs ensembles to retain their original superior optical properties as in solution. QDs with thick shells are proven effective in suppressing the inter-dot interaction and preserving the emission properties for QDs solids. However, lattice strain–induced defects may form as the shell grows thicker, resulting in a notable photoluminescence quenching. Herein, a well-type CdxZn1−xS/CdSe/CdyZn1−yS QDs is proposed, where ternary alloys CdZnS are adopted to match the lattice parameter of intermediate CdSe by separately adjusting the x and y parameters. The resultant thick-shell Cd0.5Zn0.5S/CdSe/Cd0.73Zn0.27S QDs reveal nonblinking properties with a high PL QY of 99% in solution and 87% in film. The optimized quantum dot light-emitting diodes (QLEDs) exhibit a luminance of 31547.5 cd m−2 at the external quantum efficiency maximum of 21.2% under a bias of 4.0 V. The shell thickness shows great impact on the degradation of the devices. The T50 lifetime of the QLEDs with 11.2 nm QDs reaches 251 493 h, which is much higher than that of 6.5 and 8.4 nm QDs counterparts. The performances of the well-type thick-shell QLEDs are comparable to state-of-the-art devices, suggesting that this type of QDs is a promising candidate for efficient optoelectronic devices.  相似文献   
8.
The objective of this work is to study electron-vibrational interaction (EVI) and concentration quenching and their manifestation in experimental photoluminescence spectra of Cu+ ion in various lithium based phosphors namely, Li2SO4, LiNaSO4 and LiKSO4. The main parameters of EVI, such as the Stokes shift, Huang-Rhys factor and zero-phonon line positions, were estimated. The studied systems shows strong electron lattice coupling. The validity of results was established by modeling the shape of the emission spectra, which was found to be in good agreement with experimental photoluminescence spectra. The concentration quenching study is also carried out for these compounds. The studied systems correspond to the nearest neighbor energy transfer mechanism.  相似文献   
9.
通过带有PEG官能团的双丙烯酸酯大分子单体的RAFT环聚合反应合成含有十一元环重复结构的PEG大分子刷.不同PEG长度的连接1,2,3-三氮唑的双丙烯酸酯大分子单体通过点击化学反应合成.PEG侧链的较大位阻效应影响双丙烯酸酯大分子单体的聚合行为,以致于双丙烯酸酯大分子单体优先进行环化聚合反应而不发生交联反应.核磁数据和凝胶渗透色谱证明高效的环化聚合反应,而且没有副反应发生.PEG大分子刷在紫外光激发下有较强的荧光,而荧光则强烈依赖于聚合物刷的浓度,这归因于环聚合物在水中的聚集.PEG大分子刷的荧光能被DNA淬灭.  相似文献   
10.
采用付玫瑰苯胺与对苯二甲醛通过希夫碱偶联反应制备了新型的多孔芳香骨架材料.经过FTIR,TGA,PXRD,SEM,TEM和Ar吸附等分析方法对多孔芳香骨架材料的成键方式和骨架结构进行了表征.分析结果显示,该多孔芳香骨架材料具有优异的热稳定性(350℃仅失重5%)和溶剂稳定性,其Langmuir比表面积约为472m~2/g.紫外光谱和荧光光谱测试分析表明,该材料在苯、甲苯和氯苯等芳香化合物环境中无明显的荧光强度变化.然而在硝基爆炸物环境中会发生灵敏的、专一的荧光淬灭现象.该多孔材料可应用于硝基爆炸物的检测.  相似文献   
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