查看更多>>摘要：We present a quantitative analysis of the deviations introduced by the anisotropy of the fluorescence on the measurement of the quantum yield of emission. Errors of up to 40% can be encountered depending on the characteristics of both sample and apparatus. Additionally, we have analyzed the effect of anisotropy on the study of fluorescence quenching in Stern-Volmer experiments, and on the reconstruction of time-resolved emission spectra. We conclude that the use of polarizers is recommended provided they are well characterized. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A novel N-acylhydrazone with pharmaceutical importance was subject of structural and IR/VCD investigations in the solid state. In the crystal structure, dimers of anion-cation pairs are stabilized by H-bonding and ionic interactions. Some less common interaction types, like C=N center dot center dot center dot C-NH3+ (sigma-hole) interactions, hydrazone-aromatic interactions and dispersive contacts of the CF3 groups are also present in the crystal. Satisfactory reproduction of the solid state IR and VCD spectra required that quantum-chemical calculations be done on a tetramer (four cation-anion pairs) cut out from the crystal structure, exhibiting key intermolecular interactions. Ten DFT functionals were assessed as to the agreement between the calculated and experimental spectra. Various approaches to scaling of the calculated frequencies were applied. The best results were yielded with individual (optimized) frequency scaling factors (FSFs) and band half-widths at half maximum-(HWHM) for four separate spectral subregions. The best matching between the experimental and theoretical spectra (according to SimIR, SimVCD and SimVDF indices) was found for the B3PW91 functional, however, a few other functionals follow closely in the ranking. Based on the quantum chemical calculations, spectral assignments have been made. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：One of the most used characterization techniques in the field of alkaline activated cements studies is infrared spectroscopy. Its prominence lies in that it allows characterizing mixtures during the alkaline activation by providing information about the vibrations of the chemical bonds in the molecular units, both of amorphous and crystalline products. This research paper is aimed at examining the influence of the concentration of calcium hydroxide (CH), sodium hydroxide (SH), temperature and curing time on the structure of alkaline activated cements, based on coal fly ash, from the deconvolution of the infrared spectrum between 4000 and 400 cm(-1). 9 mixtures were analyzed by infrared spectroscopy at 3 and 28 days after curing, based on a surface's response experimental design by varying the amount of SH (5.17-10.83 M), CH (2.93-17.07% ash's wt.) and the curing temperature (25, 35 and 45 degrees C). The results show significant variations in the frequency and area of the deconvolved bands in the functional groups: 0-H (2600-3800 cm(-1)), C-O (1580 and 1350 cm(-1)) and T-O (T: Si (Al), 1300-400 cm(-1)). Such variations are due to the reorganization of the forming elements (present in the ash) network and modifiers (present in CH and SH) for the formation of cementing gels C-(A) -S-H (970 cm(-1)) and N-A-S-H (1009 cm(-1)). (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A fluorescent probe Hcy-Im bearing an indolium-hemicyanine structure was designed and synthesized to compare its responses to four anions, namely HSO3-, CN-, HS- and ClO-. The results disclosed that Hcy-Im reacted with all these four anions in 5% DMSO-PBS buffer with different speeds and spectral changes. HcyIm responded to HSO3- markedly quicker than CN- and HS-, and it responded to CN- a little quicker than HS- while the response to ClO- was much slower than the other three anions. The detection limits for these four anions were calculated to be 0.15 mu M, 1.32 mu M, 2.07 mu M and 2.29 mu M, respectively. The characteristic conjugated C=N+ and C=C bonds in Hcy-Im were responsible for the responses towards these four anions via a Michael addition-rearrangement reaction, a 1, 2-addition reaction or an oxidation reaction. These different sensing mechanisms were verified by 1HNMR and HRMS. Thus, it could be inferred that hemicyanine-based fluorescent probe could detect HSO3- sensitively and selectively while the interference of HSO3- should not be neglected when it was used for the detection of CN-, HS- and ClO-. Moreover, as HSO3-, HS- and ClO- are anions endogenously generated in human bodies, enough attention should be paid to the presence of physiological level of these three anions in certain tissues when hemicyanine-based fluorescent probe is applied for the detection of biorelevant analytes in biological samples. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：HClO/ClO-, as one of important reactive oxygen species, is a highly reactive unavoidable by-product generated from normal cell metabolism. In recent years, efficient method for detectiing HClO/ClO- is of great important to research its pathological or physiological function in bio-systems. In this work, we have constructed a fluorescent probe (P-Hc) with ratiometric signal for sensing HClO/ClO- in aqueous solution, physiological saline and different serums based on 2-(benzo[d]thiazol-2-yl)phenol dye. The structure of P-Hc was characterized by NMR and HRMS spectrum. The sensing mechanism has also been verified by H-1 NMR spectrum. The P-Hc displays good sensitivity and selectivity for HClO/ClO- with a limit of detection (LOD) of 2.03 x 10(-6) M. Furthermore, P-Hc has been applied for sensing HClO/ClO- in physiological saline and different serums. Thus, P-Hc may provide a novel method for ratiometric fluorescent sensing HClO/ClO- in bio-samples. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In the paper, a novel fluorescent probe based on Ag2S QDs/g-C3N4 composite was synthesized by loading Ag2S quantum dots (Ag2S QDs) on the surface of g-C3N4 through in-situ synthesis method and developed to detect Nitrofurazone (NFZ) sensitively. The results showed that the linear detection range of Ag2S QDs/g-C3N4 to NFZ was 0-30 mu M, with a low detection limit of 0.054 mu M. The results of time-fluorescenceresolved spectroscopy and UV-vis absorption spectroscopy exhibited that the possible detection mechanism of Ag2S QDs/g-C3N4 to NFZ was proposed to be Internal Filtration Effect (IFE). Moreover, Multiwfn wavefunction analysis was employed to uncover the possible interaction between the Ag2S QDs/g-C3N4 and NFZ, thereby further revealing the fluorescence detection mechanism from the scale of atoms. Combining experiments and theoretical calculations, we proposed the sensing mechanism of the formation of non-fluorescent ground state complex linked by hydrogen bonds. This work indicated that the Ag2S QDs/g-C3N4 composite processed the ability to detect NFZ efficiently and sensitively. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Photothermal therapy is one of the promising approaches toward cancer treatment. To date, several compounds have been developed for this application, among which nanoparticles are attracting ever-increasing attention. One of the obstacles in developing efficient photothermal nanoparticle agents is their off-target effect which is mainly mediated via non-specific interactions with proteins. Such interaction not only reduces the bioavailability of the agent but also will cause protein aggregation that can be lethal. So, gaining knowledge on the mechanisms mediating such interactions will facilitate development of more effective agents. Our last studies showed the mechanism of action of two modified gold nanoparticles, folic acid functionalized gold nanoparticles (FA-AuNPs) and gold shelled Fe(3)O(4 )nanoparticles (AuFeNPs), as photothermal agents. In the current work, we focus on the interaction of these two NPs with human serum albumin (HSA) and human hemoglobin (Hb) as model proteins. The complex formation between NPs and proteins was investigated by fluorescence spectroscopy, dynamic light scattering and circular dichroism. Our data distinguishes the very distinct mode of interaction of charged and neutral NPs with proteins. While the interaction of neutral AuFeNP to proteins is protein dependent, charged nanoparticles FA-AuNP interact indistinguishably with all proteins via electrostatic interactions. Moreover, complexes obtained from FA-AuNPs with proteins are more stable than that of AuFeNP. However, the secondary structure content of proteins in the presence of NPs indicates the insignificant effect of NPs on the secondary structure of these proteins. Our data propose that the charge functional-ization of the NPs is an effective way for modulating the interaction of nanoparticles with proteins. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：In this work, we reported a novel nanozyme (3D V2O5-MoS2/rGO) by decorating MoS2 nano-flowers and V2O5 nanoparticles on reduced graphene oxide (rGO). The 3D V2O5-MoS2/rGO nanocomposites exhibited intrinsic peroxidase mimicking activity and catalyzed the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to produce a blue colored product in the presence of H2O2. Compared with horseradish peroxidase (HRP), 3D V2O5-MoS2/rGO nanocomposites displayed high catalytic velocity (V-max) and affinity (K-m) for substrates (H2O2 and TMB). The study of the catalytic mechanism showed that the reduction of V5+ and the oxidation of S2- in the 3D V2O5-MoS2/rGO nanocomposites accelerate electron transfer between H2O2 and TMB, which enhanced the peroxidase mimicking activity of 3D V2O5-MoS2/rGO nanocomposites. The as-synthetized 3D V2O5-MoS2/rGO could be used for the colorimetric detection of H2O2 in the range of 20.00-800.00 mu M with the LOD of 12.40 mu M (3r/S). Moreover, the 3D V2O5-MoS2/rGO could also be used for the detection of glucose in the range of 4.00-300.00 mu M with the LOD of 3.99 mu M (3 sigma/S). In addition, the as-synthetized novel peroxidase mimics has good applicability for sensitive colorimetric determination of glucose in human blood samples and artificial urine samples, and has broad application prospects as a multi-functional sensing platform in clinical diagnosis. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A stable luminescent Cd-MOF, formulated as [Cd(L)(0.5)(4, 4'-bpy)(0.5)]center dot H2O (1), (H4L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 4, 4' -bpy = 4, 4'-bipyridine), is acquired under solvothermal conditions. 1 exhibits stability in the pH range from 1.5 to 12.2 and in different organic solvents. 1 can detect tetracycline and nitrobenzene by fluorescence quenching with high sensitivity and selectivity. The detection limits are 0.14 mu M and 14 nM, respectively. Interestingly, 1 can encapsulate Tb3+ and sensitize its characteristic peaks. Moreover, the fluorescent ink is prepared by using the luminescent properties of the Tb3+@Cd-MOF. The light of the fluorescent ink disappears in an acid gas HCl atmosphere and then reappears in an alkaline gas ammonia atmosphere. This phenomenon can be repeated and the reason for this phenomenon is also explained in the article. Therefore, Tb3+@Cd-MOF has huge application potential in information encryption. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonate (PFOS) are two typical perfluorinated compounds (PFCs) that poss potential ecological toxicity. In this work, a fluorescence and resonance light scattering (RLS) dual-readout strategy for the detection of PFCs at picomole level based on the water-soluble CdTe quantum dots (CdTe QDs) has been proposed. It is found that the CdTe QDs exhibit a quenching in the presence of PFCs and thus serve as useful probes for PFCs. The linear ranges are 0.032-10.0 nM with a limit of detection(LOD) of 32.02 pM for PFOA and 0.044-15.0 nM with a LOD of 43.96 pM for PFOS, respectively. Meanwhile, PFCs can form complexes with CdTe QDs in acid medium, resulting in remarkable RLS signals. The enhanced RLS intensities are in proportion to the concentrations of PFOA and PFOS, respectively. And the linear ranges are 0.048-5.0 nM with a LOD of 47.78 pM for PFOA, and 0.057-5.0 nM with a LOD of 56.72 pM for PFOS, respectively. This dual-mode detection increases the reliability of the measurement. The proposed method is simple, sensitive and cost-effective, with potential applications in environmental monitoring and assessment. (C) 2021 Elsevier B.V. All rights reserved.
NSTL
Elsevier