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A magnetic and carbon dot based molecularly imprinted composite for fluorometric detection of 2,4,6-trinitrophenol
摘要： A magnetic molecularly imprinted composite was prepared by reverse microemulsion using carbon dots (CDs), Fe3O4 as the co-nucleus, and a molecularly imprinted polymer (MIP; with 2,4,6-trinitrophenol as the template) acting as recognition sites. The composite of type CD/Fe3O4@MIPs was characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), zeta potentiometric analysis, X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The results showed that the composite MIP has a spherical shape with average diameter of 200 nm. They also showed that the composite contains core-shell structures with several Fe3O4 nanoparticles and CDs embedded in each of the microsphere. The composite can extract 2,4,6-trinitrophenol (TNP) and has an imprinting factor of 3.6. It has high selectivity and sensitivity for TNP which acts as a quencher of the fluorescence of the CDs (with excitation/emission maxima at 370/470 nm). The limit of detection of this fluorometric TNP assay is 0.5 nM. The method was successfully applied to the determination of TNP in spiked tap water and river water samples, and recoveries ranged from 89.4% to 108.5% (with an RSD of <6%).
关键词： Fluorescence quenching,Fe3O4 nanoparticles,Stern-Volmer plot,Environmental pollutants,Reverse microemulsion method,Selective recognition,Molecularly imprinting
更新于2025-09-23 15:23:52
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Online Third-Order Liquid Chromatographic Data with Native and Photoinduced Fluorescence Detection for the Quantitation of Organic Pollutants in Environmental Water
摘要： Third-order liquid chromatographic data were generated online for the simultaneous quantitation of six organic environmental pollutants. The employed strategy consists in reducing the linear flow rate at the column outlet. A postcolumn UV reactor and a fluorimetric detector allowed to properly record both photoinduced and native excitation?emission fluorescence matrices (EEPIFMs and EEFMs, respectively). The obtained third-order liquid chromatography data were chemometrically processed with the multivariate curve resolution?alternating least-squares model. The sensitivity of the overall analytical method was enhanced by a very simple solid-phase extraction with C18 membranes, to be able to successfully apply it to natural water samples tested as real matrices. Favorable detection limits for the investigated pollutants, ranging from 0.02 to 0.27 ng mL?1, were attained, with relative prediction errors between 2 and 7%. Since the studied samples contain uncalibrated interferents, the applied strategy achieves the second-order advantage. Implications regarding the potential achievement of the third-order advantage are discussed.
关键词： multivariate curve resolution?alternating least-squares,solid-phase extraction,second-order advantage,third-order advantage,third-order liquid chromatographic data,photoinduced fluorescence detection,organic environmental pollutants
更新于2025-09-23 15:21:21
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Ultra-Compact Low-Noise Broad-Band Upconversion Detector at 6 μm
摘要： State-of-the-art mid-infrared (MIR: 2 – 15 μm) direct detectors (e.g. semiconductor based HgCdTe, PbS, PbSe, and microbolometer) suffer from high background noise when operating at room temperature. Low noise detection therefore requires multi-stage or cryogenic cooling (-195°C) and perfect shielding to avoid temperature fluctuations [1]. Such systems easily become sophisticated and bulky, non-suitable for widespread applications. As the MIR spectral range, especially around 6 μm, is very relevant for spectroscopic-imaging of bio-molecules (protein, lipids), tissues (cancer, tumour), or for sensing of environmental pollutants (CH4, NO, NO2, SO2), high resolution spectroscopic systems in the 6 μm range is much in need. The numbers of pixels in typical HgCdTe or microbolometer based array detectors are limited to few 100s, making them less than ideal for fast high resolution broad-band spectroscopy. This work aims to solve that problem, by using frequency upconversion detection (UCD) [2]. In the presence of a strong near-infrared (NIR) LASER pump (at 1.03 μm), the MIR signal (6 μm) is translated to the NIR wavelength range (below 1 μm) using parametric frequency conversion in a nonlinear crystal (AgGaS2), without losing the spectral information encoded in the MIR signal. After upconversion, a standard silicon-CCD based spectrometer (pixel number = 2064) is used to detect the upconverted signal. In this way, high resolution, sensitive spectroscopic measurements can be performed, without the need for sophisticated cooling. The proposed upconversion system is based on a diode (940 nm) pumped Yb:YAG based solid state LASER operating at 1.03 μm, where the nonlinear crystal AgGaS2 (bulk, 5×5×10 mm3) is placed inside the LASER cavity to access the high intracavity power (Fig. 1(a)). This arrangement essentially gives higher upconversion efficiency. A Globar (heat source at ~ 800°C) is used as MIR illumination in the 6 μm range, giving an upconverted signal in the 880 nm range (grey area plot in Fig. 1(b)). In comparison to the previous demonstrations [3], the primary novelties of this system are (i) long-wavelength pumping of the laser, meaning that the pump diode wavelength (940 nm) is longer than the upconverted wavelength (< 900 nm), simplifying the spectral filtering of the upconverted signal, (ii) the LASER (at 1.03 μm) cavity is only 4 cm long, which makes the footprint of the upconversion module < 10 cm2, and (iii) no moving parts are needed in the upconversion spectrometer system (Fig. 1(a)). Using this system, we have successfully upconverted the 6 – 6.8 μm range (800 nm wide) within a single acquisition (50 ms) using Type-II birefringent phase matching in an AgGaS2 crystal. The wide bandwidth of the upconversion detection is achieved by exploiting non-collinear interaction between the pump LASER and the MIR signal inside the crystal. As an experimental verification we measured the MIR absorption spectrum of a polystyrene film placed at the MIR input side (Fig. 1(b)). Further details and results will be presented. We believe this is a promising route towards a small footprint, low-noise, efficient upconversion detector for high resolution spectroscopic application, directly in the molecular fingerprint wavelength range.
关键词： upconversion detection,spectroscopic-imaging,mid-infrared,environmental pollutants,nonlinear crystal
更新于2025-09-12 10:27:22
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Nanoscale Materials in Water Purification || Photocatalysis of Graphene and Carbon Nitride-Based Functional Carbon Quantum Dots
摘要： Day by day, global energy demands increase due to the rapid consumption of depleting fossil fuels and environmental pollution. This has led to the search for materials capable of both energy conversion and elimination of environmental pollutants through the aid of renewable solar energy. This is a promising approach for meeting future energy requirements and eliminating environmental pollutants. In this pursuit, semiconductor photocatalysts have immense potential for solving both energy and environmental issues. To date, numerous semiconductor materials have been explored, including those of metal oxides, chalcogenides, borates, titanates, tungstates, vanadates, zirconates, oxyhalides, and metal-based interstitial compounds. However, the majority of these suffer from limitations such as complex synthesis procedures, limited light absorption range due to their wide band gap, high cost, and toxicity-related issues. Over the past decade, carbon-based nanomaterials have gained attention in the field of photocatalysis. Many recent articles have placed emphasis upon metal-free carbon-based photocatalytic systems for degradation of organic pollutants and hydrogen production from water splitting. The prime merit of these nanomaterials is that they originate from naturally abundant constituent elements such as carbon, nitrogen, and oxygen, making them more economical than their metal-based counterparts. Most reported carbon-based photocatalysts have tunable band gap energies, enhancing their optical absorption range. Band gap energy can be tuned by varying synthesis conditions and precursors, resulting in the formation of nanomaterials with different morphologies. The preparation procedures for most carbon-based nanomaterials are less complex than those of metal-based materials.
关键词： water splitting,energy conversion,semiconductor photocatalysts,graphene,carbon nitride,quantum dots,carbon-based nanomaterials,hydrogen production,solar energy,environmental pollutants,photocatalysis
更新于2025-09-09 09:28:46
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Fabrication of ternary visible-light-driven semiconductor photocatalyst and its effective photocatalytic performance
摘要： Heterogeneous semiconductor photocatalysis has been considered as a cost-effective alternative for the eliminating hazardous pollutants and generating sustainable energy. Graphene, a 2D allotrope of carbon, has received significant attentions due to its outstanding properties. In this work, a highly efficient visible-light-driven ternary heterostructure semiconductor RGO/Ag2O/Ag2WO4 (RGAAW) Ag-based photocatalyst was prepared and its photocatalytic activity was evaluated by photodegradation of methylene orange (MO). The morphology, structure and optical absorption properties of the as-prepared RGAAW were characterized by SEM, XRD, XPS, FT-IR and UV?vis DRS, respectively. The obtained result was found that the as-prepared RGAAW exhibited the excellent photocatalytic activity, which was almost 11.5 and 7 times as high as those of individual Ag2O and Ag2WO4, respectively. The enhancement of photocatalytic performance could be attributed to the reduced graphene oxide sheets can function as an electron collector and transporter to lengthen the lifetime of the charge carriers. Moreover, the as-prepared RGAAW showed excellent stability toward the photodegradation of methyl orange (MO). The possible mechanism of photocatalytic activity enhancement was proposed.
关键词： environmental pollutants,visible-light-driven,Photocatalyst
更新于2025-09-04 15:30:14