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Host Sensitized Lanthanide Photoluminescence from Post-synthetically Modified Semiconductor Nanoparticles Depends on Reactant Identity
摘要： This work investigates the photoluminescence characteristics where cadmium selenide (CdSe) and zinc sulfide (ZnS) nanoparticles are treated post-synthetically by the trivalent lanthanide cations (Ln3+) [Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb] separately to form either CdSe/Ln or ZnS/Ln nanoparticles. Host sensitized Ln3+ emission was found to be present only in CdSe/Eu, CdSe/Tb, ZnS/Eu, ZnS/Tb and ZnS/Yb nanoparticles. In all the cases tuning of emission of the nanoparticles has been observed, irrespective of the presence or absence of host sensitization. The elemental compositions of CdSe and ZnS nanoparticles upon post-synthetic treatment show a remarkable difference. Incorporation of lanthanides in the nanoparticles is evident with significant alteration in the anionic content, and complete cation exchange of either Cd2+ or Zn2+ by Ln3+ has not been detected; as evaluated from energy dispersive X-ray spectroscopy. Further evaluation on this comes from considering thermodynamic parameters of inter cation interaction. In cases where the host sensitized Ln3+ emission have been observed, luminescence lifetime measurements reveal significant protection of Ln3+ in the nanoparticles. Noticeable difference in photophysical properties for a given Ln3+ has been realized in the two hosts. The photophysical observations have been rationalized using (i) charge trapping mediated host sensitized dopant emission, (ii) autoionization of excited electrons, and (iii) environment induced photoluminescence quenching. The post-synthetic modification discussed in the present work provides an easy and less synthetically demanding room temperature based protocol to avail lanthanide incorporated (doped) semiconductor nanoparticles that can potentially use the unique emission properties of the lanthanide cations.
关键词： Semiconductor Nanoparticles,Host Sensitization,Trivalent Lanthanides,Photoluminescence,Post-synthetic Modification
更新于2025-09-23 15:23:52
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A comprehensive photophysical and NMR investigation on the interaction of a 4-methylumbelliferone derivative and cucurbit[7]uril
摘要： The host-guest interaction of a 7-hydroxycoumarin (3-[2-(diethylamino)ethyl]-7-hydroxy-4-methylcoumarin, 3ED4MU) with cucurbit[7]uril, CB7, was investigated in aqueous solution. From the steady-state fluorescence Job plot and 1H NMR spectroscopy the formation of a 1:1 inclusion complex, with a binding constant of 1.75×105 M?1 was obtained. Time-resolved fluorescence data in water, DMSO and dioxane for 3ED4MU and for umbelliferone (UM, here taken has the model compound) show that the decays are double or triple-exponentials mirroring the presence of excited neutral (N*), anionic (A*), tautomeric (T*) and zwiterionic (T*’) species (the latter only present in 3ED4MU). In the time-resolved experiments, the interaction of 3ED4MU with CB7 is mirrored by an increase of the pre-exponential factor associated to the zwiterionic species (thus giving support for the stabilization of this species when interacting with CB7) and a dramatic change in the pKa* value (from ~ 0.5 to ~8), associated to a displacement of the water environment probed by 3ED4MU.
关键词： Time-resolved fluorescence,Host-guest chemistry.,Binding constant,Fluorescence,Hydroxycoumarins,Cucurbit[7]uril
更新于2025-09-23 15:23:52
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A Fluorescence Sensing Determination of 2, 4, 6-Trinitrophenol Based on Cationic Water-Soluble Pillar[6]arene Graphene Nanocomposite
摘要： We describe a selective and sensitive fluorescence platform for the detection of trinitrophenol (TNP) based on competitive host–guest recognition between pyridine-functionalized pillar[6]arene (PCP6) and a probe (acridine orange, AO) that used PCP6-functionalized reduced graphene (PCP6-rGO) as the receptor. TNP is an electron-deficient and negative molecule, which is captured by PCP6 via electrostatic interactions and π–π interactions. Therefore, a selective and sensitive fluorescence probe for TNP detection is developed. It has a low detection limit of 0.0035 μM (S/N = 3) and a wider linear response of 0.01–5.0 and 5.0–125.0 for TNP. The sensing platform is also used to test TNP in two water and soil samples with satisfying results. This suggests that this approach has potential applications for the determination of TNP.
关键词： reduced graphene,trinitrophenol,host–guest recognition,cationic pillar[6]arene
更新于2025-09-23 15:22:29
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Anthracene-based cyclophanes with selective fluorescent responses for TTP and GTP: insights into recognition and sensing mechanisms
摘要： Three anthracene-based cyclophanes have been synthesized and their binding properties towards nucleoside triphosphates have been studied. A new polycyclic amine derived from dearomatized anthracene has been identified as a major side product in the reaction between 9,10-anthracenedicarboxaldehyde and diethylenetriamine. Its structure has been determined by the single crystal X-Ray analysis. The cyclophanes have been found to form 1:1 complexes with all nucleoside triphosphates as well as with pyrophosphate in a buffered aqueous solution at pH 6.2. A turn-on fluorescence response has been observed for all nucleotides except for GTP, which demonstrated strong fluorescence quenching. The strongest turn-on fluorescence answer has been observed for the largest receptor 3 in the presence of TTP. Based on the NMR and fluorescence experiments two major binding modes for nucleotide complexes have been identified.
关键词： macrocycle,host-guest chemistry,nucleotide recognition,synthetic receptor,fluorescence sensing
更新于2025-09-23 15:22:29
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Photoswitchable Host-Guest Systems Incorporating Hemithioindigo and Spiropyran Units
摘要： We cover selected examples of the incorporation of hemithioindigo and spiropyran units in one of the binding partners of synthetic host-guest systems. In some of the simplest systems, isomerization of the switch simply modulates the thermodynamic stability of the two isomeric host-guest complexes. In the presence of more than two binding partners, the isomerization of the molecular switch alters the composition of the multicomponent host-guest system producing a shuttling process of one of the components between different hosts. In others, the isomerization process controls the uptake and release of some of the components from/to the bulk solution. We show that the understanding of the isomerization mechanisms of the molecular switches and the effects produced by the external stimuli are essential for the design of complex and responsive supramolecular host-guest systems. The physicochemical properties of the hemithioindigo and spiropyran molecular photoswitches are complementary, providing different avenues to their applications in solution and material science.
关键词： Spiropyrans,Hemithioindigos,Host-Guest Systems,Supramolecular Assemblies,Photoswitches
更新于2025-09-23 15:22:29
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Fluorescent Calixarene Scaffolds for NO Detection in Protic Media
摘要： Here, we present the first fluorescent water-soluble conjugated calixarene scaffolds that are capable of detection of NO gas. Two different scaffolds, one based on a 5,5’-Bicalixarene structure and its isomer bearing two distantly conjugated calixarene moieties, have been synthesized. While the fluorescence of both isomers is quenched upon either passing of NO gas or generating it in-situ from diethylamine NONOate, the bicalixarene-based scaffold showed a significantly stronger response. We also present an example of a dye encapsulation strategy to achieve the detection of NO at longer wavelengths than in the parent calixarene host. Finally, a conjugated polymer bearing 5,5’-Bicalixarene scaffold has also been prepared and demonstrated enhanced sensitivity compared with the monomer due to the molecular wire effect.
关键词： conjugated systems,nitric oxide,host-guest chemistry,fluorescent probes,Calixarene
更新于2025-09-23 15:22:29
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Template-driven dense packing of pentagonal molecules in monolayer films
摘要： The integration of molecules with irregular shape into a long-range, dense and periodic lattice represents a unique challenge for the fabrication of engineered molecular scale architectures. The tiling of pentagonal molecules on a 2D plane can be used as a proof-of-principle investigation to overcome this problem since basic geometry dictates that a two-dimensional (2D) surface cannot be filled with a periodic arrangement of pentagons, a fundamental limitation that suggests that pentagonal molecules may not be suitable as building blocks for dense films. However, here we show that the 2D covalent organic framework (COF) known as COF-1 can direct the growth of pentagonal guest molecules as dense crystalline films at the solution/solid interface. We find that the pentagonal molecule corannulene adsorbs at two different sites on the COF-1 lattice, and that multiple molecules can adsorb into well-defined clusters patterned by the COF. Two types of these dense periodic packing motifs lead to a five-fold symmetry reduction compatible with translational symmetry, one of which gives an unprecedented high molecular density of 2.12 molecules/nm2.
关键词： host-guest system,fivefold symmetry,scanning probe microscopy,pentagonal molecules
更新于2025-09-23 15:21:21
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The synthesis of water-soluble phosphate pillar[5]arenes functionalized graphene as a fluorescent probe for sensitive detection of paraquat
摘要： We describe a selective and sensitive fluorescence platform for the detection of paraquat (PQ) based on competitive host–guest recognition between phosphate pillar[5]arenes (PWP5) and probe (Safranine T, ST) with using PWP5 functionalized reduced graphene (PWP5-rGO) as the receptor. PQ is a positive charge molecule that is captured by PWP5 via electrostatic interactions. The host-guest interaction between PWP5 and PQ is studied by 1H NMR. Therefore, a selective and sensitive fluorescence sensing of detection PQ is developed. It has a linear response ranges of 0.01?2.0 and 2.0?50.0 μM and a low detection limit of 0.0035 μM (S/N=3) for PQ. The sensing platform is also used to test PQ in two water samples with satisfying results. It suggests that this approach has potential applications for the determination of PQ.
关键词： phosphate pillar[5]arenes,paraquat,reduced graphene,host–guest recognition
更新于2025-09-23 15:21:21
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Preparation and luminescent properties of mesoporous (SBA-15)-Eu2O3 nano materials
摘要： The CH3-(SBA-15) and (SBA-15)-Eu2O3 host-gust nanocomposite materials were synthesized by post-synthesis method, ultrasonic synthesis method (UM) and ultrasonic assisted synthesis methods (UAM). The X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscope (TEM) analysis and nitrogen adsorption-desorption method were used to observe the structure, the surface morphology and the chemical composites of the prepared products. The luminescent properties, and the luminescent intensity of the samples were studied by excitation and emission spectra. The results showed that, for the (SBA-15)-Eu2O3 composite materials, the hexagonal pore structure of the SBA-15 molecular sieve was maintained. The luminescent intensity of the UM sample was about 6 times higher than that of the mechanical mixture of SBA-15 and nano-Eu2O3 (5 wt %). The excitation spectrum intensity was 2 times higher than that of the mechanical mixture.
关键词： (SBA-15)-Eu2O3,Luminescence,SBA-15 molecular sieve,Trimethyl chlorosilane,Host-gust nanocomposite material
更新于2025-09-23 15:21:21
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Design of hole transport type host for stable operation in blue organic light-emitting diodes
摘要： Molecular design of the hole transport type host for mixed host was investigated to improve the lifetime of the phosphorescent organic light-emitting diodes. A negative polaron stabilizing hole transport type host design was employed and the effect of the negative polaron stabilizing unit was investigated. Dibenzofuran or benzonitrile was introduced as the negative polaron stabilizing unit in the bicarbazole backbone structure of the hole transport type host. Two host materials were synthesized and the comparison of them proposed that the negative polaron stabilizing unit is a key to the lifetime of the phosphorescent organic light-emitting diodes. The dibenzofuran and benzonitrile embedded bicarbazole hosts performed better than the mCBP host. The dibenzofuran and benzonitrile modified bicarbazole hosts demonstrated high external quantum efficiency of 18.6 and 19.1%, respectively and lifetime extension by 30% compared with the conventional host without the negative polaron stabilizing unit.
关键词： Negative polaron,Lifetime,Mixed host,Hole type host
更新于2025-09-23 15:21:01