Fluorescence Spectroscopy
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2021 ◽  
Author(s):  
Lan Binh Nguyen Thi ◽  
Nguyen Thi Thanh Truc ◽  
Ngoc Tran Nguyen Thi ◽  
Dinh Khang Vu ◽  
Byeong-Kyu Lee

Abstract Plastic food containers are being used popularly, generating a waste of about 115 million tons in Vietnam. Such waste is causing environmental and health issues. This study conducted a field survey with 309 local people and selected 59 samples out of 135 plastic food containers collected in Go Vap district, Vietnam. Collected plastic samples identified compositions were PET 13.6 %, PP 28.8 %, PS 16.9 %, and 40.7 % X. Although most people are aware of the toxicity of plastics, plastics are still widely used due to their convenience and price with easy use and purchase. Collected plastic samples were classified based on the plastic type using recycling code and quantitatively analyzed with X-ray fluorescence spectroscopy method to assess concentrations of Cd, Sb, Pb, Hg, Sn, Cr, Br, Cl, and S. Most of these collected plastic samples (91.5 %) were found to contain 8/9 hazardous substances and most elements contained in these plastics were below their standard thresholds. However, elements Cl and Sb exceeded their safe thresholds, reached the highest concentrations of 1990.3 ppm and 469.2 ppm, respectively. Thus, additional health risks need to be assessed using the USEtox model. Finally, this study proposed a screening process to assess the risk of toxicity of elements contained in plastic food containers through ISO 31000:2018.


Author(s):  
Muhammad Farooq Saleem Khan ◽  
Mona Akbar ◽  
Jing Wu ◽  
Zhou Xu

Abstract In recent years, the application of fluorescence spectroscopy has been widely recognized in water environment studies. The sensitiveness, simplicity, and efficiency of fluorescence spectroscopy are proved to be a promising tool for effective monitoring of water and wastewater. The fluorescence excitation-emission matrix (EEMs) and synchronous fluorescence spectra have been widely used analysis techniques of fluorescence measurement. The presence of organic matter in water and wastewater defines the degree and type of pollution in water. The application of fluorescence spectroscopy to characterize dissolved organic matter (DOM) has made the water quality assessment simple and easy. With the recent advances in this technology, components of DOM are identified by employing parallel factor analysis (PARAFAC), a mathematical trilinear data modeling with EEMs. The majority of wastewater studies indicated that the fluorescence peak of EX/EM at 275nm/340nm is referred to tryptophan region (Peak T1). However, some researchers identified another fluorescence peak in the region of EX/EM at 225-237nm/340-381nm, which described the tryptophan region and labeled it as Peak T2. Generally, peak T is a protein-like component in the water sample, where T1 and T2 signals were derived from the <0.20µm fraction of pollution. Therefore, a more advanced approach, such as an online fluorescence spectrofluorometer, can be used for the online monitoring of water. The results of various waters studied by fluorescence spectroscopy indicate that changes in peak T intensity could be used for real-time wastewater quality assessment and process control of wastewater treatment works. Finally, due to its effective use in water quality assessment, the fluorescence technique is proved to be a surrogate online monitoring tool and early warning equipment.


2021 ◽  
Vol 10 (4) ◽  
pp. 154-161
Author(s):  
А. V. Marukhlenko ◽  
Т. V. Maksimova ◽  
Т. V. Pleteneva ◽  
М. A. Morozova

Introduction. The production, standardization and quality control process of various dietary supplements containing chelated zinc requires validated quantitative assessment methods. In this work, we propose an X-ray fluorescence spectroscopy (XRF) technique for determining the zinc content in the composition of coordination compounds using the example of a synthesized chelate complex with methionine.Aim. To synthesize Zn(Met)2 chelate complex, to develop and validate a method for its quantitative analysis using the XRF method.Materials and methods. The synthesized zinc chelate complex was investigated by IR spectroscopy. The XRF method was used to develop a method for quantifying the zinc content in the synthesized complex. We used dry mixtures of zinc sulfate monohydrate and L-methionine (Met) in a molar ratio of Zn to Met – 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 1 : 16 and also aqueous solutions of zinc sulfate and L-methionine in a molar ratio of Zn to Met 1 : 2 with Zn concentrations from 0.5 to 100 mmol/l as calibration standards. Complexometric titration was used as an arbitration method for the quantitative determination of zinc content in the samples under study.Results and discussion. The IR spectrum of chelate complex confirmed the presence of a donor-acceptor bond between Zn2+ and the nitrogen atom of amino group in methionine. The titration results showed chelate compounds have a composition corresponding to the stoichiometric formula Zn(Met)2. XRF analysis of dry standard mixed samples demonstrated the presence of matrix effect, that makes impossible an accurate assessment of zinc content in the chelate compound. According to the XRF spectra of aqueous solutions containing zinc sulfate and methionine in a ratio of 1 : 2 at a zinc concentration of 0.5; 1; 2; 3; 4; 5; 10; 25; 50 and 100 mmol/L, a calibration graph was constructed – the dependence of the fluorescence signal intensity for the Kα line of zinc on the concentration of zinc in the solution (r = 0.9996). The method was evaluated by the following validation parameters: specificity, linearity, correctness, precision, and analytical range. The specificity of the validated method was proven in the presence of copper, iron, and silver.Conclusion. The developed method make it possible to determine with sufficient precision and correctness the content of Zn2+ in its aqueous solutions of inorganic and organic nature by the XRF method in the concentration range from 3 to 100 mmol/l without the influence of the matrix.


2021 ◽  
Vol 63 (11) ◽  
pp. 40-43
Author(s):  
Minh Hieu Nguyen ◽  
◽  
Binh Duong Le ◽  
Anh Tuan Mai ◽  
Thi Binh Nguyen ◽  
...  

Research and synthesis of photosensitive purpurin 18 (Pp-18) from nature is one of the topics that many research groups are interested in and developing. In this study, the authors defined some characteristics of Pp-18 synthesised from chlorophyll a - a substance isolated from Spirulina. The results showed that Pp-18 had good dispersion in acetone at 478.5 nm (R2=0.98285) and reached 98%. Fluorescence spectroscopy of Pp-18 in acetone was measured at a concentration of 70 ppm, wavelengths 365.39, 417.62, and 557.96 nm. The fluorescence lifetime of Pp-18 in acetone solution was 2.85 ns.


Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1434
Author(s):  
Indri Badria Adilina ◽  
Robert Ronal Widjaya ◽  
Luthfiana Nurul Hidayati ◽  
Edi Supriadi ◽  
Muhammad Safaat ◽  
...  

Biochar (BCR) was obtained from the pyrolysis of a palm-oil-empty fruit bunch at 773 K for 2 h and used as a catalyst for the hydrodeoxygenation (HDO) of guaiacol (GUA) as a bio-oil model compound. Brunauer–Emmet–Teller surface area analysis, NH3 and CO2-temperature-programmed desorption, scanning electron microscope–dispersive X-ray spectroscopy, CHN analysis and X-ray fluorescence spectroscopy suggested that macroporous and mesoporous structures were formed in BCR with a co-presence of hydrophilic and hydrophobic sites and acid–base behavior. A combination of infrared, Raman and inelastic neutron scattering (INS) was carried out to achieve a complete vibrational assignment of BCR. The CH–OH ratio in BCR is ~5, showing that the hydroxyl functional groups are a minority species. There was no evidence for any aromatic C–H stretch modes in the infrared, but they are clearly seen in the INS and are the majority species, with a ratio of sp3–CH:sp2–CH of 1:1.3. The hydrogen bound to sp2–C is largely present as isolated C–H bonds, rather than adjacent C–H bonds. The Raman spectrum shows the characteristic G band (ideal graphitic lattice) and three D bands (disordered graphitic lattice, amorphous carbon, and defective graphitic lattice) of sp2 carbons. Adsorbed water in BCR is present as disordered layers on the surface rather than trapped in voids in the material and could be removed easily by drying prior to catalysis. Catalytic testing demonstrated that BCR was able to catalyze the HDO of GUA, yielding phenol and cresols as the major products. Phenol was produced both from the direct demethoxylation of GUA, as well as through the demethylation pathway via the formation of catechol as the intermediate followed by deoxygenation.


Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7148
Author(s):  
Xiangdong Fang

Transition metal catalyzed coupling reaction strategy has been utilized in the synthesis of two novel BN-perylenes starting from halogenated BN-naphthalene derivatives. The molecular structures and packing modes of BN-perylenes were confirmed by NMR spectroscopy and X-ray single-crystal diffraction experiments. Their photophysical properties were further investigated using UV-vis and fluorescence spectroscopy and DFT calculations. Interestingly, the isosteric BN-insertion in perylene system resulted in stronger π-π stacking interaction both in solid and solution phases. The synthesized BN-perylenes are proved to be highly stable and thus provide a new valuable platform for novel organic materials applications which is otherwise inaccessible to date.


2021 ◽  
Vol 5 (11) ◽  
pp. 304
Author(s):  
Martha Kafetzi ◽  
Stergios Pispas ◽  
George Mousdis

The aim of this work is to investigate the preparation, the optical properties, and the stability over time of a colloidal organic–inorganic hybrid perovskite (CH3NH3PbBr3)/random copolymer P(MMA-co- DMAEMA) system. Different ratios of perovskite to copolymer were used to study its effect on stability and properties. The optical properties were investigated by UV-Vis and fluorescence spectroscopy. Dynamic light scattering was used to determine the size, and the size polydispersity of the colloidal hybrid particles; while morphology was investigated by transmission electron microscopy. Photoluminescence decay studies revealed the interaction of the random copolymer with the perovskite. Finally, thin-films were prepared, to investigate the optical properties of the samples in the absence of the solvent. High temporal stability of the optical properties of thin hybrid films was observed under certain conditions.


2021 ◽  
Author(s):  
Drishtant Singh ◽  
Samiksha . ◽  
Seema Madhumal Thayil ◽  
Satwinder Kaur Sohal ◽  
Anup Kumar Kesavan

Abstract An expression system based on the cry gene regulatory elements was constructed. The Terminator region of cry gene from B. thuringiensis subsp. kurstaki HD-1 was cloned in pSG1151 plasmid downstream to gfpmut1. The promoter region of the cry gene was amplified to give three different reading frames. The Promoter region of cry gene was cloned in pSG1151T plasmid upstream to gfpmut1. The expression of GFP under the promoter/terminator expression system was evaluated by checking the expression of gfpmut1 under the same promoter. The GFP content of pSG1151 and three constructs; pDSA1, pDSA2 and pDSA3 were compared by fluorescence spectroscopy. The fluorescent intensity of pSG1151 and pDSA1 were compared at time interval of 6 hours upto 72 hours. Both the samples showed detectable fluorescence that increased with time up to 12 hours, but the increase in the fluorescence of pDSA1 was 3 times higher as compared to pSG1151. A cold peptidase gene was cloned under the control of the cry promoter. The transformed E.coli DH5α colonies were patched on skim milk agar plates and the clones of pSG1151CP and pDSA1CP were compared on the basis of zone of clearance. The zone of clearance of pDSA1CP was much higher as compared to that of pSG1151CP. The cell-free supernatant of Bacillus sp. S1DI 10 and recombinant pDSA1CP collected at different time points was assayed for the specific activity of the extracellular protease. At 72 hours the protease activity in pDSA1CP was 2.7 fold higher compared to that of wild Bacillus sp. S1DI 10.


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