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Effect of Toxic Metal Ions on Photosensitized Singlet Oxygen Generation for Photodegradation of Polyaromatic Hydrocarbon Derivatives and Inactivation of <i>Escherichia coli</i>
摘要： Here we report an experimental study of the effect of toxic metal ions on photosensitized singlet oxygen generation for photodegradation of PAH derivatives, Anthracene-9,10-dipropionic acid disodium salt (ADPA) and 1,5-dihydroxynapthalene (DHN) and photoinactivation of E. coli bacteria by using cationic meso-tetra(N-methyl-4-pyridyl)porphine tetrachloride (TMPyP) as a singlet oxygen photosensitizer. Three s-block metals ions, such as Na+, K+, and Ca2+ and five toxic metals such as Cd2+, Cu2+, Hg2+, Zn2+, and Pb2+ were studied. The s-block metal ions showed no change of the rate of photodegradation of ADPA or DHN by TMPyP whereas a dramatic change in the photodegradation of ADPA and DHN were observed in the presence of toxic metals. The maximum photodegradation rate constants of ADPA and DHN were observed for Cd2+ ions [(3.91 ± 0.20) × 10-3 s-1 and (7.18 ± 0.35) × 10-4 s-1, respectively]. Strikingly, the photodegradation of ADPA and DHN was almost completely inhibited in the presence of Hg2+ ions and Cu2+ ions. A complete inhibition of growth of E. coli was observed upon visible irradiation of E. coli solutions with TMPyP and toxic metal ions particularly, Cd2+, Hg2+, Zn2+, and Pb2+ ions, except for Cu2+ ions where a significantly slow inhibition of E. coli’s growth was observed.
关键词： E. coli,photodegradation,toxic metal ions,photosensitized singlet oxygen generation,PAH derivatives,TMPyP,photoinactivation
更新于2025-09-23 15:21:01
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DNA enzyme mediated ratiometric fluorescence assay for Pb(II) ion using magnetic nanosphere-loaded gold nanoparticles and CdSe/ZnS quantum dots
摘要： Based on the inner filter effect mechanism of quantum dots, a ratiometric fluorescence nanoprobe was constructed for the determination of Pb(II) ion. Green emitting quantum dots conjugated with DNA substrate (DNA2) acted as donors providing green fluorescence, while gold nanoparticles coupled with DNA enzyme (DNA1) as acceptors quench the green fluorescence. Meanwhile, Fe3O4 nanosphere served as magnetic substrates to facilitate separation process and red fluorescence as an “inner rule” to eliminate the background signal. In the presence of Pb(II) ion, the DNA1 specifically recognize and capture Pb(II) ion with enhanced catalytic activity, which can cleave DNA2 and “turn on” the green fluorescence (I540), while the red fluorescence (I630) remained unchanged. In this way, the ratio of I540/I630 reflects the Pb(II) ion in the system, enabling the quantitative and selective determination of Pb(II) ion over nine different metal ions. Under optimal conditions, the ratiometric fluorescence assay showed good linearity (R2 = 0.98) within the range 10 to 100 ng mL?1. The limit of detection (LOD) was calculated to be 1.79 pg mL?1 (S/N = 3, n = 3, ±3.8%). The proposed fluorescence nanoprobe provides better sensitivity and accuracy than non-ratiometric signal evaluation for Pb(II) ion determination.
关键词： Fluorescence nanoprobe,Inner rule,Magnetic separation,Tea sample,Metal ions,Inner filter effect
更新于2025-09-23 15:19:57
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Luminescent Sulfur Quantum Dots for Colorimetric Discrimination of Multiple Metal Ions.
摘要： The classical chemistry of sodium thiosulphate was applied to synthesize luminescent Sdots where elemental sulfur produced in situ was etched with NaOH. This method notably reduces the synthesis time of Sdots in comparison to the previously reported etching technique of bulk sulfur. The as-synthesized Sdots exhibited excitation dependent photoluminescence with a QY of 2.5 %, photostabality under UV light irradiation, excellent dispersibility in aqueous medium and also the stability even after several weeks. Notably, no emission was observed due to the oxidation of PEG-400 during the course of reaction. The Sdots was then employed as a dual function probe for the sensing of metal ions. Using fluorimetric method, Sdots showed preferential selectivity towards the Co2+ metal ions. However, a single probe Sdots can colorimetrically distinguish multiple metal ions such as Co2+, Cr6+ and Pb2+ by displaying color change on the immediate addition of analytes. Furthermore, the color change of Sdots is demonstrated with the help of hue images and hue spectra (or histogram) that will help in the development of Sdots based portable device. The present study contributes to the further advancement of this emerging field as a promising single-element nanomaterial an alternative to luminescent metallic nanomaterials.
关键词： Colorimetric Discrimination,Photoluminescence,Hue,Sodium Thiosulphate,Sdots,Metal Ions
更新于2025-09-23 15:19:57
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On-off-on fluorescent carbon dots from waste tea: Their properties, antioxidant and selective detection of CrO42?, Fe3+, ascorbic acid and L-cysteine in real samples
摘要： In this work, we reported an economical plant-based hydrothermal method for one-pot green synthesis of water-soluble carbon dots (Tea-CDs) by using waste tea extract as a carbon source. The synthesized Tea-CDs were characterized by UV-visible, fluorescence, FT-IR, TEM, XPS and XRD. The Tea-CDs were found to remove hydroxyl and superoxide anion radical in vitro. In addition, the Tea-CDs exhibited bright blue fluorescence under UV-light (λex=365 nm), and the fluorescence could be effectively quenched by CrO4 2- and Fe3+ ions. Meanwhile, the fluorescence of Tea-CDs-CrO4 2- and Tea-CDs-Fe3+ systems could be again easily recovered by ascorbic acid (AA) and L-cysteine (L-Cys). As an on-off-on fluorescent nano-sensor of the Tea-CDs, the sensitive detection of CrO4 2-, Fe3+, AA and L-Cys were all performed, showing that the good linear relationships between fluorescence intensity of Tea-CDs and concentration of all testing samples. Finally, the sensors successfully detected CrO4 2-, Fe3+, AA and L-Cys in commercially available real samples with satisfactory recovery ranges. The prepared sensors offer distinct advantages including low cost, simple handling, good sensitivity and high selectivity.
关键词： carbon dots,waste tea,L-cysteine,ascorbic acid,on-off-on fluorescent nano-sensor,metal ions
更新于2025-09-19 17:15:36
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A Fluorescence Probe for Metal Ions Based on Black Phosphorus Quantum Dots
摘要： Fluorescence method for detecting metal ions has advantages of fast detection speed, simple operation, and low price over the conventional methods. Black phosphorus quantum dots (BP QDs) have high photoluminescence quantum yield and modifiable surface, which have great potential in the field of fluorescent probes. In this study, high quality BP QDs are prepared by pyrolysis method and are first time used as trace metal ion probes in both organic solutions and aqueous solutions. The detection limits of Hg2+ and Cu2+ in the aqueous solution are 5.3 × 10?9 m and 1.6 × 10?6 m, respectively. In addition, the detection limits of Cu2+ in the organic solution are 16 × 10?6 m. The fluorescence quenching mechanism based on the calculation of the electronic structure and adsorption energy of BP QDs after adsorption of metal ions is further explained. The results provide a new promising fluorescence probe for trace metal ions without the help of organic molecules.
关键词： electron transfer,fluorescence,black phosphorus,metal ions
更新于2025-09-19 17:13:59
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Enhanced emission from thermally stable Eu3+ doped CaB2Si2O8 red phosphors via alkali metal modification for W-LEDs application
摘要： M+/Eu3+ (M = Li, Na, K) co-doped CaB2Si2O8 phosphors have been synthesized by a solid-state reaction approach. XRD measurements confirm that the phase purity of the CaB2Si2O8 host is maintained after the introduction of alkali metal ions and Eu3+ ions. The emission intensity of Eu3+ ions is enhanced by a factor of 1.75 and 1.55 with the incorporation of Li+ and Na+ ions, respectively, originating from the charge compensation and improved asymmetry in the crystal field, while the addition of K+ ions to the composition results in a decreased luminescence intensity due to the structural-defect-related quenching. Temperature dependent measurement reveals that the prepared phosphor exhibits excellent thermal stability with 81% at 423 K of the integrated emission intensity at 298 K. A white light-emitting diode (W-LED) device is fabricated based on the synthesized Eu3+ doped CaB2Si2O8 red phosphor modified by Li ions. All these results indicate that the synthesized phosphor is a promising red-emitting material for W-LEDs application.
关键词： Red phosphor,Eu3+ ions,W-LEDs,Alkali metal ions
更新于2025-09-16 10:30:52
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Simultaneous detection of mercury (II), lead (II) and silver (I) based on fluorescently labelled aptamer probes and graphene oxide
摘要： We have developed a fluorescence quantitative analysis method for the simultaneous detection of Hg2+, Pb2+ and Ag+ based on fluorescently labeled nucleic acid aptamer probes and graphene oxide. By this method, three nucleic acid aptamer probes (PHg, PPb, PAg) were designed. The carboxyl fluorescein (FAM), tetramethyl-6-carboxyrhodamine (TAMRA) and cyanine-5 (Cy-5) were respectively selected as fluorophore of aptamer probes, and graphene oxide (GO) was chosen as quencher. In general, these probes were on free single-stranded state and adsorbed on the surface of GO via π-π interactions, which brought fluorophores of probes and GO into close proximity. Due to the fluorescence resonance energy transfer (FRET) occurred between fluorophores and GO, the fluorescence was quenched and fluorescence signals were all weak. Under the optimal condition, fluorescence intensities of three fluorophores exhibited a good linear dependence on corresponding ions concentration. The detection limit for Hg2+, Pb2+ and Ag+ were 0.2 nmol/L, 0.5 nmol/L and 2 nmol/L (3σ, n=11). Average recoveries of this method were 97.56 - 104.92%, which indicated the method had a high accuracy and low detection limit. In addition, this proposed method has good selectivity, and there was no crosstalk effect among these probes.
关键词： Graphene oxide,Simultaneous detection,Metal ions,Fluorescence,Aptamer
更新于2025-09-16 10:30:52
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Spatial charge relaxation in glasses poled in the air and argon atmospheres
摘要： Thermal poling of a multicomponent silicate glass was performed in air and in argon atmospheres at various voltages, and the temperature dependences of the depolarization currents (TSDC) in the poled glasses were studied. In addition, the concentration profiles of univalent and bivalent cations in subanodic regions of the poled glasses were measured with EDS and SIMS techniques. The difference in the displacements of bivalent ions at poling of the glasses in closed and open anode configurations allowed us to identify “frozen” spatial charge relaxation peaks observed in the TSDC measurements and to relate these peaks to hydrogen and bivalent metal ions relaxation.
关键词： spatial charge relaxation,silicate glass,thermal poling,depolarization currents,hydrogen and bivalent metal ions relaxation
更新于2025-09-12 10:27:22
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Detection of lead Using Thioglycolic Acid Capped ZnSe and ZnSe@ZnS core-shell Quantum Dots
摘要： Herein, we proffer a sensitive and selective sensor using ZnSe and ZnSe@ZnS quantum dots (QDs), for detection of toxic metal ions at nm level. It has been found that the TGA capped ZnSe and ZnSe@ZnS QDs were apparently sensitive to Pb2+ ions as perceptible from their fluorescence quenching measurements. However, in case of few common heavy metal ions such as Zn2+, Co2+, Fe2+, , Mg2+, Cu2+, Ni2+ and Cd2+ ions, negligible quenching compared to Pb2+ ions was noted. Hence, we have successfully detected Pb2+ ions in aqueous solutions based on the photoluminescence (PL) spectroscopy. The observed linearity range was from 10 NM to 100 nM for both Pb2+ ions. An alternative QD based sensor for the spectroscopic detection, and concentration quantification of Pb2+ ions is proposed.
关键词： Metal ions,Photoluminescence,Thioglycolic acid,Quantum dots,Core-shell QDs
更新于2025-09-12 10:27:22
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Two-Dimensional Fluorescent Strategy Based on Porous Silicon Quantum Dots for Metal-Ion Detection and Recognition
摘要： A two-dimensional photoluminescent (2D PL) detection strategy was established based on luminescent porous silicon (LuPSi) with wide-size-distributed silicon quantum dots and abundant surface chemistry. Owing to the intrinsic nature of LuPSi, interaction or reaction between analytes and LuPSi may cause static, dynamic, oxidation-induced, and deposition-induced quenching. By monitoring of both the PL intensity change and peak shift of LuPSi, the 2D PL detection strategy could discriminate di?erent analytes. Detection and recognition of di?erent metal ions in real water samples using a single peak were realized. Compared with the existing array-based methods, the 2D PL approach signi?cantly simpli?ed the sensing element and detection process.
关键词： metal ions,quantum dot array,two-dimensional photoluminescence,luminescent porous silicon,recognition
更新于2025-09-12 10:27:22