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Highly selective and sensitive detection of catecholamines using NaLuGdF4:Yb3+/Er3+ upconversion nanoparticles decorated with metal ions
摘要： We developed a novel optical sensor for sensitive and selective detection of catecholamines based on upconversion nanoparticles (UCNPs) decorated with different metal ions (UCNP-Men+). 1,2-ethanedithiol was chosen as a surface additive to synthesize the NaLuGdF4:Yb3+/Er3+ UCNPs by one-step at 200 °C. The as-prepared UCNPs exhibited a strong emission under the continuous excitation at 980 nm. It was found that catecholamines could be more effectively detected in the presence of UCNP-Fe3+, whereas, dopamine and epinephrine were detected selectively using UCNP-Li+ and UCNP-Cu2+ sensors, respectively. Under the optimum conditions, the limit of detections (LODs) for catecholamines, dopamine, and epinephrine are 2.8, 2.5, and 2.4 nM, respectively, with good linearity in the range of 5–320 nM for total catecholamines and 5–30 nM for dopamine and epinephrine. The developed method has been successfully applied to detect dopamine and epinephrine in human urine samples with good accuracy and satisfactory recovery.
关键词： Upconversion nanoparticles,Human urine,Metal ion decorated,Catecholamines,1,2-ethanedithiol
更新于2025-09-23 15:23:52
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Fuel Waste to Fluorescent Carbon Dots and Its Multifarious Applications
摘要： Herein, we report the fluorescent carbon dots (KCDs) from kerosene fuel soot via simple one pot oxidative acid treatment. The obtained KCDs were thoroughly characterized by pivotal techniques. The prepared KCDs are 5 nm sized quasi-spherical particles and exhibited an outstanding stability against pH, NaCl and light irradiation. Intriguingly, the KCDs display an excitation wavelength independent emissive property. Further, the KCDs were successfully utilized for multifarious applications such as photoinduced electron transfer (PET) and sensing studies. For PET studies, charged porphyrins (tetra pyridyl and tetra sulphonato) were selected and the fluorescence of associated porphyrin was quenched and the quenching is due electron transfer. The lower recombination rate obtained from transient absorption spectral studies suggests that KCDs can be used as electron shuttling material in a cascade system of photovoltaic device. On the other hand, the fluorescent nature of KCDs was used for the selective and sensitive detection of explosives and metal ions. The detection limit for picric acid, Cu2+ and Fe3+ is found to be 86 ng/ml, 15.3 ng/ml and 0.36 μg/ml respectively. Moreover, the unreacted soot during the acid treatment has been calcined and used as an affordable filter bed for waste water treatment.
关键词： Explosives,PET,Kerosene Soot,Carbon dots,Metal ion detection
更新于2025-09-23 15:21:21
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Enhancing Galvanic Replacement in Plasmonic Hollow Nanoparticles: Understanding the Role of the Speciation of Metal Ion Precursors
摘要： Hollow nanostructures offer great potential for plasmonic applications due to their strong and highly tunable localized surface plasmon resonance. The relationship between the plasmonic properties and geometry of hollow nanoparticles, such as core-shell size ratio, concentricity of the cavity and porosity of the wall, is well documented. Nanoscale galvanic replacement provides a simple, versatile and powerful route for the preparation of such hollow structures. Here we demonstrate how the efficiency of reductant-assisted galvanic replacement processes can be enhanced by controlling the degree of hydration and hydrolysis of the metal ion precursor using pH and pL as key control parameters (by analogy to pH, the letter p in the expression pL is used to indicate the decimal cologarithm associated with the concentration of the ligand L). Adjusting precursor speciation prior to the sacrificial template’s hollowing process offers a new strategy to tune the morphology and optical properties of plasmonic hollow nanostructures.
关键词： co-reduction,localized surface plasmon resonance,nanoscale galvanic replacement,hollow nanoparticle synthesis,Ag-Au, Ag-Pd and Ag-Pt alloys,aqueous metal ion speciation
更新于2025-09-23 15:21:01
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Fluorescence quenching of molybdenum disulfide quantum dots for metal ion sensing
摘要： In the present work, we have used hydrothermally synthesized in situ functionalized MoS2-QDs for a sensitive (limit of detection ~ 2.06 μM) and selective detection of Fe3+ ions. A detailed study of fluorescence quenching behavior for MoS2-QDs in the presence of Fe3+ ions has been performed using the Stern–Volmer plot, modified Stern–Volmer plot, and time-resolved photoluminescence measurements. Absorption based titration spectra and time-resolved photoluminescence measurements confirmed the fluorescence quenching is static with three decay times originated from the three different fluorescing sites. Interestingly, it is found that emission spectra consist of three bands at positions ~ 450 nm (P1, ~ 2.76 eV), ~ 475 nm (P2, ~ 2.61 eV), and ~ 503 nm (P3, ~ 2.46 eV). These peaks show a systematic quenching with the increasing concentration of Fe3+ ions. Quenching constants corresponding to these emission bands are found of the order of ~ 103 M?1. Large values of bimolecular quenching constants (~ 1011 M?1 s?1) suggest a strong binding interaction between MoS2-QDs and Fe3+ ions. Furthermore, to understand the fluorescence quenching of MoS2-QDs in the presence of Fe3+ ions, a ground-state complex formation-based mechanism has been proposed and elucidated in detail.
关键词： Nanostructures,UV/Vis spectroscopy,Metal ion sensing,Time-resolved photoluminescence,Fluorescence spectroscopy
更新于2025-09-23 15:21:01
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Auto-cleaning paper-based electrochemiluminescence biosensor coupled with binary catalysis of cubic Cu2O-Au and polyethyleneimine for quantification of Ni2+ and Hg2+
摘要： Inspired by the pop-up greeting cards, a 3D collapsible auto-cleaning paper-based electrochemiluminescence (ECL) biosensor (CAPEB) with different functions of signal collection and residual multiple cleaning, is developed for sensitive detection of Ni2+ and Hg2+ by simply regulating its 3D configurations. The multiple fluidic paths and the hollow-channel structure were firstly integrated into the paper substrate, realizing simultaneously repetitive auto-cleaning of the two working electrodes. For achieving ultrasensitive Ni2+ and Hg2+ monitoring, binary catalysis consisting of the intermolecular co-reaction (H2O2 and N-(4-Aminobutyl)-N-ethylisoluminol (ABEI)) and intramolecular catalysis (polyethyleneimine (PEI)-ABEI) were introduced. Specifically, silver nanospheres with a large specific surface area and excellent conductivity were grown on the paper working electrode and served as the sensor substrate for fixing PEI-ABEI and Ni2+-specific DNAzyme. With the assistance of DNAzyme, Cu2O-Au and ferrocene (Fc) labeled strand S2 were immobilized on electrode surface through the hybridization reaction, and catalyzed H2O2 to generate reactive oxygen species, promoting the luminescence of ABEI. In the existence of Ni2+, DNAzyme was activated followed by cleavage of strand S2 to induce the release of Fc, which quenched the ECL signal of ABEI, eventually realizing the detection of Ni2+. Similarly, for sensitive quantification of Hg2+, full thymine (T) bases strand S3 was modified on surface of Cu2O-Au and anchored Hg2+ by T-Hg2+-T pairing interaction. The ECL intensity was decreased along with increasing of Hg2+ due to the quenching effect of Hg2+ on ECL emission of ABEI. Based on this ingenious system, the detection of Ni2+ and Hg2+ had high sensitivity, wide linear ranges, and low detection limits. The results indicated that the integration of a multi-channel structure into a paper device chips opened new opportunities for designing promising paper-based devices for metal ions diagnosis.
关键词： electrochemiluminescence,N-(4-Aminobutyl)-N-ethylisoluminol,auto-cleaning,Cu2O-Au,paper-based device,heavy metal ion
更新于2025-09-23 15:21:01
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Metal-Ion Displacement Approach for Optical Recognition of Thorium: Application of a Molybdenum(VI) Complex for Nanomolar Determination and Enrichment of Th(IV)
摘要： An azine-based molybdenum (Mo(VI)) complex (M1) is exploited for selective detection of thorium (Th(IV)) ions through a metal-ion displacement protocol. Th(IV) displaces Mo(VI) from M1 instantly leading to the formation of the Th(IV) complex, having orange-red emission. Consequently, a red shift of the emission wavelength along with 41-fold ?uorescence enhancement is observed. This unique method allows detection of Th(IV) as low as 1.5 × 10?9 M. The displacement of Mo(VI) from M1 by Th(IV) is established by spectroscopic studies and kinetically followed by the stopped-?ow technique. The displacement binding constant for Th(IV) is notably strong, 4.59 × 106 M?1. Extraction of Th(IV) from aqueous solution to the ethyl acetate medium using M1 has been achieved. The silica-immobilized M1 e?ciently enriches Th(IV) from its reservoir through solid-phase extraction. Computational studies (density functional theory) support experimental ?ndings.
关键词： Solid-phase extraction,Molybdenum(VI) complex,Fluorescence enhancement,Thorium detection,Metal-ion displacement
更新于2025-09-23 15:21:01
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Optical fiber sensors for measurement of heavy metal ion concentration: A review
摘要： With the increasing of water pollution problems, detection of heavy metal ion concentration in water environment becomes significant. Optical fiber sensor, with its particular advantages of small-size, anti-electromagnetic interference, chemical inertness, remote and real-time monitoring ability, has become an ideal platform for detection of heavy metal ion concentration. In this paper, we briefly review the current research progress of heavy metal ion sensors based on optical fiber technology. Five main measurement methods are described, including optical absorbance method, fiber grating method, modal interference method, plasmonic method, and fluorescence method. The sensing mechanisms, sensing structures, sensing materials, and sensing characteristics of different kinds of measurement methods are introduced and summarized. Furthermore, the advantages and disadvantages of each measurement method are analyzed. Finally, the future development directions of optical fiber heavy metal ion sensors are also discussed.
关键词： Water pollution,Optical fiber sensor,Concentration measurement,Heavy metal ion sensor
更新于2025-09-23 15:19:57
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Controllable synthesis of transition metal ion-doped CeO2 micro/nanostructures for improving photocatalytic performance
摘要： Ceria (CeO2) micro/nanostructures with various sizes and shapes were successfully synthesized by doping with a series of transition metal ions without any surfactant or template. The crystal structure, morphology, and photocatalytic performance of CeO2 and Co-, Zr-, Cu-doped CeO2 were characterized. The lattice parameters, which indicate the crystal structure distortion and change of Ce4+, were changed by incorporating a transition metal into the CeO2. Doping with transition metal ion could broaden the absorption range from ultraviolet to visible region and enhance the concentration of oxygen vacancies, which exhibited a significantly lower optical band than pure CeO2. The photocatalytic studies revealed that CeO2 with a spate of oxygen vacancies displayed a higher photocatalytic activity than pure CeO2 in degrading the organic pollutant rhodamine B (RhB). Furthermore, the O2? and ?OH radicals formed during photocatalysis process were revealed by means of nitrotetrazolium blue chloride (NBT) reduction method and a terephthalic acid (TA) fluorescence probe method, respectively, which discovers that radicals were crucial for the degradation of RhB. The H2-TPR confirmed that a small amount of transition metal ions significantly affected the oxidation state of the surface cations and oxygen vacancies. This study clearly reveals the effects of different transition metal ion dopants on the morphologies and photocatalytic performance of transition metal ion-doped CeO2 micro/nanostructures.
关键词： oxygen vacancy,CeO2,metal ion-doping,morphology,photocatalytic activity
更新于2025-09-23 15:19:57
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Metal-ion bridged high conductive RGO-M-MoS2 (M = Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) composite electrocatalysts for photo-assisted hydrogen evolution
摘要： Efficient photo-electrocatalysts for hydrogen evolution reaction (HER) are synthesized using a facile one-step hydrothermal method. With metal-ion bridges, highly dispersed molybdenum disulfide (MoS2) nanolayers are vertically grown on the reduced graphene oxide (RGO) to form RGO-M-MoS2 photocatalysts for HER, where M = Fe3+, Co2+, Ni2+, Cu2+ and Zn2+. The results show that the cross-bridging ions can modulate the MoS2 growth priority and act as efficient charge transfer channels between RGO and MoS2, and combine the advantages of the high conductivity of graphene with the photo-electrochemical activity of MoS2. The metal-ion bridged MoS2-M-RGO heterostructures demonstrate superior catalytic activity toward hydrogen evolution reaction (HER) in acid medium, evidenced by the remarkable higher catalytic current density at low overpotential compared with that of MoS2-RGO without metal-ion bridge. This study provides a novel and facile route for establishing efficient composite photo-electrocatalysts for water splitting to generate hydrogen.
关键词： hydrogen evolution reaction,MoS2 nanosheets,reduced graphene oxide,metal-ion bridge
更新于2025-09-19 17:15:36
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Selective Ultrasensitive Optical Fiber Nanosensors Based on Plasmon Resonance Energy Transfer
摘要： The facet of optical fibers coated with nanostructures enable the development of ultraminiature and sensitive (bio)chemical sensors. The reported sensors until now lack of specificity and the fabrication methods offer poor reproducibility. Here, we demonstrate that by transforming the facet of conventional multimode optical fibers onto plasmon resonance energy transfer (PRET) antenna surfaces the specificity issues may be overcome. To do so, a low cost chemical approach was developed to immobilize gold nanoparticles on the optical fiber facet in a reproducible and controlled manner. Our nanosensors are highly selective as PRET is a nanospectroscopic effect that only occurs when the resonant wavelength of the nanoparticles matches that of the target parameter. As an example, we demonstrate the selective detection of picomolar concentrations of copper ions in water. Our sensor is 1,000 times more sensitive than state of the art technologies. An additional advantage of our nanosensors is their simple interrogation; it comprises of a low-power light emitting diode, a multimode optical fiber coupler, and a miniature spectrometer. We believe that the PRET-based fiber optic platform reported here may pave the way of the development of a new generation of ultra-miniature, portable, and hypersensitive and selective (bio)chemical sensors.
关键词： plasmonics,chemosensor,nanoparticles,optical fiber,metal ion
更新于2025-09-19 17:13:59