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Aqueous synthesis of glutathione-capped CuInS2/ZnS quantum dots-graphene oxide nanocomposite as fluorescence a??switch OFFa?? for explosive detection
摘要： This work reports a simple and fast aqueous preparation of CuInS2/ZnS-graphene oxide (CIS/ZnS-GO) nanocomposite as a fluorescence "switch OFF" probe for the fluorescence detection of 2, 4, 6-trinitrophenol (TNP.) – a raw material for various explosive devices. The as-synthesized nanocomposites was characterised using Ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, high resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Raman scattering. The PL studies revealed that the adsorption of TNP onto GO via p-p stacking enhanced the charges transfer from CuInS2/ZnS-GO to the analyte. The limit of detection (LOD) for the analyte is 57 lΜ.
关键词： Nanocomposite,Explosive,Quenching,Trinitrophenol,Fluorescence,Detection
更新于2025-11-19 16:46:39
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Highly Sensitive and Selective Fluorescent Sensor based on a Multi-Responsive Ultrastable Amino-Functionalized Zn(II)-MOF for Hazardous Chemicals
摘要： A microscale amino-functionalized Zn(II)-MOF, namely [Zn(NH2-bdc)(4,4’-bpy)] (1) (NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid and 4,4’-bpy = 4,4’-bipyridine), has been successfully synthesized, structurally characterized and further utilized as multi-responsive fluorescent sensor for highly sensitive and selective detection of Cr(VI) and 2,4,6-trinitrophenol (TNP). Compound 1 features non-porous 5-fold interpenetrated 3D framework with the Lewis basic sites including the uncoordinated amino and carboxylate groups on the framework for anchoring and recognizing the guest. 1 exhibits not only excellent water and thermal stability but also tolerance to acidic and basic media over an extensive pH range of 2-12. This ultrastable material can sensitively and selectively detect Cr2O7 2- and CrO4 2- in water based on the luminescent quenching with relatively low limits of detection (2.21 μM for CrO4 2- and 1.30 μM for Cr2O7 2-). Moreover, the unprecedented solvent-dependent luminescent response of 1 as a fluorescent probe for high-efficiency TNP detection was observed. Significantly, 1 not only displays high sensitive fluorescent enhancement upon TNP binding in ethanol but also exhibits fluorescent quenching toward TNP in water with very low limits of detection of 4.47 nM and 0.32 μM in ethanol and water, respectively. This work reports the first example of the utilization of MOF as a sensor for the detection of TNP based on dual responsive luminescence. Importantly, 1 can be simply and rapidly regenerated, displaying excellent recyclability after the sensing experiments.
关键词： Multi-responsive fluorescent sensors,Fluorescent quenching,Metal-organic framework,2,4,6-trinitrophenol,Fluorescent enhancement,Cr(VI)
更新于2025-11-19 16:46:39
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Synthesis of non-doped and non-modified carbon dots with high quantum yield and crystallinity by one-pot hydrothermal method using a single carbon source and used for ClO? detection
摘要： A facile and straightforward strategy was used to prepare carbon dots (CDs) using catechol as carbon source in one-pot hydrothermal method. The synthesis method is simple without any doping and modification and the prepared CDs do not require any post-processing. Characterizations of the obtained CDs indicated that they had high crystallinity and higher quantum yield (QY, 32%) than most non-functionalized and non-doped CDs. Noticeably, the fluorescence of CDs could be quenched with hypochlorite (ClO?) by oxidation of the residual pyrocatechol groups on the surface to o-benzoquinone exhibiting high sensitivity and selectivity for ClO? assay covered a linear range from 0.1 to 10 μM with a low detection limit of 30 nM. The results showed that the CDs provided a promising potential tool for the detection of ClO? in real water samples.
关键词： Quenching,Fluorescence,Hypochlorite,Carbon dots
更新于2025-11-19 16:46:39
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Improved negative thermal quenching effect via high sensitizer doping content in NaGdF4 based active-core/active-shell architecture
摘要： The strategies of introducing interior defects and reducing mean particle size have been applied to improve negative thermal quenching effect (TQE) in Yb3+ sensitized fluoride upconversion (UC) nanocrystals (NCs) recently. Herein, an active-core/active-shell structure with high total Yb3+ doping content is used to enhance the absorption intensity of Er3+ ions. Moreover, the Er3+ activators are doped into the shell to enable the energy migration process from activators to surface defects. In this scenario, with the rise of temperature, the suppression degree of this energy migration process is enlarged followed by an improved negative TQE. Specifically, with rising the temperature from 293 K to 413 K, the integral upconversion emission intensity of 40Yb: NaGdF4@60Yb/2Er: NaGdF4 NCs increases by ~ 8.24 times, while that of NaGdF4@20Yb/2Er: NaGdF4 NCs with a similar mean particle size only enhances ~ 3.44 times.
关键词： Yb3+ concentration,upconversion,temperature sensing,negative thermal quenching
更新于2025-11-14 17:03:37
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S, N co-doped graphene quantum dots-induced ascorbic acid fluorescent sensor: Design, characterization and performance
摘要： In this work, new detection route for ascorbic acid was designed. First, highly luminescent sulfur and nitrogen doped graphene quantum dots (S,N-GQDs) were prepared via simple hydrothermal method using citric acid and thiourea as the C, N and S sources respectively. The prepared S,N-GQDs are characterized by XRD, HRTEM, FTIR, EDS and PL. Investigations showed that prepared S,N-GQDs have a good photostability and excitation-dependent emission fluorescence. Prepared S,N-GQDs showed maximum excitation wavelength and emission wavelength at 400 and 462nm, respectively. In the following, prepared S,N-GQDs were applied as a photoluminescence probe for detection of ascorbic acid (AA). The designed sensor was based on “off-on” detection mode. The developed sensor had a linear response to AA over a concentration range of 10-500μM with a detection limit of 1.2μM. The regression equation is Y = 0.0014 X+1.2036, where Y and X denote the fluorescence peak intensity and AA concentration, respectively.
关键词： Graphene quantum dots,Quantum confinement,Fluorescence sensor,Nanostructures,Water-soluble vitamin,Quenching
更新于2025-11-14 15:32:45
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Upconversion fluorescent nanoparticles based-sensor array for discrimination of the same variety red grape wines
摘要： In this research, a novel fluorescent sensor array based on upconversion nanomaterials (UCNPs) for the discrimination of the same variety red grape wines from different manufacturers was developed. The sensor array was composed of six elements: one positively charged UCNPs modified with guanidine groups (UCNPs@GDN), two negatively charged UCNPs modified with sulfonic acid groups (UCNPs@SO3H) and phosphonic acid groups (UCNPs@PO(OH)2), respectively, and their mixture 1 (UCNPs@GDN + UCNPs@SO3H), mixture 2 (UCNPs@GDN + UCNPs@PO(OH)2) and mixture 3 {UCNPs@GDN + UCNPs@SO3H + UCNPs@PO(OH)2}. The discrimination mechanism is mainly attributed to the emission of those upconversion fluorescent nanoparticles being quenched by organic ingredients that usually exist in red grape wines. The discrimination of red grape wines was carried out by employing UCNPs@GDN, UCNPs@SO3H and UCNPs@PO(OH)2 in pH = 7.0 HEPES buffer, the mixture 1 and mixture 2 in pH = 9.0 PBS buffer, and mixture 3 in pH = 6.0 Tris–HCl buffer. Principal component analysis (PCA) of the data obtained from our established array showed obvious distinction among the nine red grape wines from different manufacturers. The present work is expected to inspire more marvellous research in the fields of UCNPs and red grape wines identification.
关键词： red grape wines,fluorescence quenching,sensor array,upconversion nanoparticles,discrimination
更新于2025-11-14 15:18:02
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Boron doped carbon dots as a multifunctional fluorescent probe for sorbate and vitamin B12
摘要： Boron doped carbon dots (B-CD) were synthesized by a one-step hydrothermal method using phenylboronic acid as the starting material. They have an average size of about 3.3 nm, with excitation/emission wavelength of 247/323 nm and a quantum yield of 12%. The B-CD is shown to be viable fluorescent probe for sorbate (PS) and vitamin B12 (VB12). The fluorescence (FL) of the B-CD is quenched in the presence of PS or VB12 mainly coming from inner filter effect (IFE), but F?rster resonance energy transfer (FRET) from the B-CD (as a donor) to PS/VB12 (as an acceptor) cannot be excluded. The probe enables PS to be detected by fluorometry with a linear response in the 0.20–24 μM concentration range and a 6.1 nM detection limit (at 3σ/slope). For VB12, the data are 0.20–30 μM and 8.0 nM.
关键词： Fluorescent probe,Sorbic acid,Fluorescence quenching ratios,Intra-day precision,Selectivity,Inter-day precision,Quenching mechanism,Real sample analysis
更新于2025-09-23 15:23:52
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Oligo(ethylene glycol)/alkyl-modified chromophore assemblies for photon upconversion in water
摘要： 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 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.
关键词： photon upconversion,photochemistry,oxygen quenching,self-assembly,triplet-triplet annihilation
更新于2025-09-23 15:23:52
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Fluorescence and absorption studies of DNA-Pd(II) complex interaction: Synthesis, spectroanalytical investigations and biological activities
摘要： Novel palladium(II) complexes (7a–7e) of substituted quinoline derivatives were synthesized. The complexes were characterized using various techniques such as thermogravimetric analysis (TGA), elemental analysis, conductance measurement, mass, absorption, infra‐red (IR), 1H NMR, 13C NMR and energy‐dispersive X‐ray spectroscopy (EDX). Complexes for herring sperm DNA (HS DNA) binding were explored and absorption titration and the binding constant (Kb) as well as Gibb's free energy were evaluated. Complex 7d exhibited the highest binding constant, therefore the thermodynamic parameters of 7d at different temperatures were evaluated. To support the results of the absorption titration, fluorescence titration, viscosity measurement and molecular docking studies were performed. The fluorescence quenching data as evaluated from Stern–Volmer equation were used to calculate KSV, K f and the number of binding sites. The results of all these studies were in good agreement with the absorption study. DNA electrophoretic mobility was performed to explore the possible application of metal complexes as artificial metallonucleases. The antibacterial activity of the complexes was accessed against different pathogenic bacteria and cytotoxicity was measured using brine shrimp and S. pombe.
关键词： Stern–Volmer equation,absorption titration,thermodynamic parameters,cytotoxicity,fluorescence quenching,artificial metallonuclease
更新于2025-09-23 15:23:52
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37ps-Precision Time-Resolving Active Quenching Circuit for High-Performance Single Photon Avalanche Diodes
摘要： Time-resolved imaging by means of single-photon avalanche diodes (SPADs) has achieved widespread interest in recent years, especially since technological progress has opened the way to the development of multichannel time-correlated single-photon counting (TCSPC) acquisition systems. Unfortunately, currently available TCSPC imagers feature relatively low performance with respect to state-of-the-art single-channel systems. A real breakthrough in this field would be the exploitation of large arrays of high-performance SPAD detectors developed by means of dedicated fabrication processes, usually referred to as custom technology. Custom-technology SPADs require external electronics potentially leading to interconnection issues for densely integrated arrays. In this paper, we present a new fully integrated front-end circuit able to provide both quenching/reset and timing functionalities while requiring a single connection toward the SPAD. This is the first fully integrated circuit reported in literature that can provide both the timing information about the photon time of arrival with a jitter as low as 37 ps and apply high-voltage pulses up to 50 V in order to meet the requirements of several detectors, including the new red-enhanced SPAD. Combining these two capabilities in a single circuit strongly reduces the complexity of the connection between an array of custom-technology SPADs and the relative external front end, thus paving the way for the exploitation of high-performance SPADs in TCSPC imaging systems.
关键词： Active Quenching Circuit,AQC,timing,time-resolved,SPAD,Single Photon Avalanche Diode,SPAD front end
更新于2025-09-23 15:23:52