Resonance Light Scattering Spectra Research Articles

Quantitative Analysis of Dominant Pollutants in Secondary Effluent via Dye Probe Technology

The linear relationship between the concentration of either bovine serum albumin (BSA) or sodium alginate (SA) and the intensity of a resonance light scattering (RLS) spectrum was established by using Congo red and neutral red as the dye probes, respectively. Moreover, the linear relationship between the concentration of humic acids (HA) and UV absorbance was determined by using toluidine blue (TB) as the dye probe. The detection of concentration range and the pH value of three kinds of standard substances were optimized. The recovery rate of bi-and tri-element samples of the standard objects was investigated by means of the dye probe analysis method. The results show that, in the appropriate concentration range, the linear correlation coefficients between the concentration of BSA, HA, or SA and the intensity of its corresponding dye probe spectrum were all high, at 0.98. The recovery rates of the three kinds of standard objects in mixed samples were all greater than 95%, and the standard errors were all less than 0.11%. Based on qualitative analysis of the proteins, polysaccharides, and humic acids in the secondary water discharge samples of urban sewage obtained via UV and RLS spectra, the dominant pollutants were confirmed in the four kinds of secondary effluent. The relative deviations of the concentration of polysaccharides and proteins measured using the dye probe technique and the national standard method ranged were from 1.2% to 0.04%.

A dual-functional spectroscopic probe for simultaneous monitoring Cu2+ and Hg2+ ions by two different sensing nature based on novel fluorescent gold nanoclusters

Here a dual-functional spectroscopic probe was developed based on novel gold nanoclusters (Au NCs) for highly selective and sensitive detection of heavy metal ions targeting copper ions (Cu2+) and mercury ions (Hg2+). Small sized Au NCs (3.9nm) with highly orange emitting fluorescent were synthesized via an one-pot reaction by using citrate-stabilized stannous ions (Sn(II)-citrate) as reducing and capping agent. The dual spectroscopic probe was conceived in such a way to utilize both the fluorescence (FL) quenched by Cu2+ and resonance light scattering (RLS) enhanced by Hg2+. Two different ions in the corresponding discrete spectral response appeared completely independent of each other by different mechanism. The intensity of fluorescence decreasing at 575nm in FL spectra and the scattering increasing at 520nm in RLS spectra, show linear relationships with Cu2+ and Hg2+ ion concentrations in the ranges of 0.5–70 and 0.25–10μmolL−1, respectively. The detection limits are as low as 0.38μmolL−1 and 0.05μmolL−1 for Cu2+ and Hg2+ ions, respectively. Furthermore, these Au NCs could be readily applied to Cu2+ and Hg2+ detection in environmental water samples, indicating it is promising to serve as a convenient, dual-functional, and label-free probe for related ions monitoring.

Spectral manifestation of surface plasmon resonance of silver nanoparticles upon interaction with water-soluble metalloporphyrins

Absorption and resonant light-scattering spectra of nanoparticles (NPs) of silver, and their complexes with water-soluble Cu(II)-5,10,15,20-tetrakis(4-N-methylpyridinium)-porphyrin (CuTMpyP4) and Fe(II)-5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (FeTSPP) have been compared. It is shown that in the presence of cationic CuTMpyP4, the band of surface plasmon resonance in the absorption and resonant scattering spectra of silver NPs is shifted to the long-wavelength region that is associated with the agglomeration of the particles caused by the Coulomb attraction between the silver particles and the porphyrin molecules. Addition of anionic FeTSPP to the silver NP solution does not lead to any spectral changes. The observed effect of silver-NP association induced by the cationic porphyrin can be used to develop an optical method for the detection of nanoparticles in solutions.

Application of cysteamine functionalized CdS hollow nanospheres in determination of Cd(II) and Pb(II) in the presence of each other by resonance light scattering technique

This work reports on the development of a method for determination of Cd(II) and Pb(II) in the presence of each other using resonance light scattering (RLS) technique. In this regard, cysteamine functionalized CdS hollow nanospheres were synthesized and used as a probe. The synthesized hollow nanospheres were fully characterized using SEM, TEM, XRD, DLS and FTIR measurements. By the aid of synchronous scanning of the excitation and emission monochromators of a conventional spectrofluorometer, RLS spectra of the synthesized nanospheres in the presence and absence of the investigated metal ions were studied, and enhancement effect of the investigated metal ions was observed. The results showed that under different optimized conditions, it is possible to determine the investigated metal ions in the presence of each other with detection limits of 9.0 and 10.0μgL−1 for Pb(II) and Cd(II), respectively. Furthermore, the real sample analysis results confirmed the method applicability for accurate analysis of real water samples.

Assembly of AuNRs and eugenol for trace analysis of eugenol using resonance light scattering technique

A new resonance light scattering (RLS) method for determining eugenol was developed using gold nanorods (AuNRs) as probes which were synthesized in our lab. The weak RLS intensity of eugenol was obviously enhanced by the use of AuNRs. All of the results from the SEM, RLS and UV spectra indicated that eugenol induced the assembly of AuNRs; thus, a new complex of AuNRs-eugenol was formed. The assembly of this new complex was achieved through a coordination bond between eugenol and AuNRs. Under optimum experimental conditions, a direct linear relationship was established between the enhancement of RLS intensity and the concentration of eugenol in the range of 0.043–10.60μgml−1 (r=0.9927). Moreover, the limit of detection (LOD) was found at a nanogram level (7.28ngml−1 by 3S0/S). The recovery and RSD (n=5) of three synthetic samples were 99.7–104.2% and 0.81–1.19%, respectively. The method was successfully employed for the analysis of eugenol in curry powder samples.

Determination of trace metallothioneins at nanogram levels with Eosin Y by resonance light scattering method

The interactions of metallothioneins with Eosin Y were studied by the absorption spectra and resonance light scattering (RLS) spectra methods. A direct RLS spectra method was applied for the determination of trace metallothioneins. The interaction of Eosin Y and metallothioneins enhanced the RLS intensity of system in Britton-Robinson buffer (pH 3.91), with the help of anionic surfactant (sodium dodecyl benzene sulphate). The mechanism was studied and discussed in terms of the RLS and UV-absorption spectra. Under optimal experimental conditions, at 366 nm, there was a linear relationship between the RLS intensity and the concentration of the metallothioneins in the range of 0.04–14.0 μg mL−1, with a correlation coefficient of r = 0.9985 and detection limit of 11.9 ng mL−1. The relative standard deviation was 3.1% (n = 11), and the average recovery was 95.2%. The method proposed was reliable, selective and sensitive in determining trace metallothioneins in human urine samples with the results in good agreement with those obtained by high-performance liquid chromatography.

Spectroscopic studies on the interaction between anthragallol and DNA using of ethidium bromide as a fluorescence probe

The interaction of DNA with anthragallol (Ant) was investigated using ethidium bromide (EB) as a fluorescence probe, and the binding mechanism of Ant with DNA was researched via viscosity measurements. The results indicate that there is a complex of Ant and DNA, as confirmed by Ultraviolet visible absorption spectroscopy (UV–vis), Fluorescent and Resonance Light Scattering spectrum (RLS) and viscosity measurements. Ant molecules could intercalate with the base pairs of DNA as evidenced by the hyperchromic effect of absorption spectra, the relative viscosity of DNA and significant increases in the melting temperature. The binding constants of Ant and DNA were obtained by the fluorescence quenching technique. Furthermore, the binding mechanisms of the reaction of Ant with DNA were also investigated. The RLS assay successfully evaluated the saturated value and measured the potential toxicity of Ant. Adriamycin, chrysophanol, rhein, and alizarin can be used as references to build a method based on the mechanism of interactions with DNA and the DNA-saturation binding value to rapidly evaluate the potential toxicity of Ant.

A novel biosensor for copper(ii) ions based on turn-on resonance light scattering of ssDNA templated silver nanoclusters.

A new ultrasensitive biosensor for copper(ii) ions was developed based on turn-on resonance light scattering (RLS) of ssDNA templated silver nanoclusters through anti-galvanic reduction (AGR). In our experimental assay, ultra-small size fluorescent C-rich ssDNA templated silver nanoclusters (C-rich ssDNA-Ag NCs) exhibit direct reduction of copper(ii) ions to elemental copper (Cu0) and the resulting Cu0 formed copper nanoparticles on the surface of C-rich ssDNA-Ag NCs spontaneously. The process produced Ag/Cu alloy nanoparticles with larger diameters, turning-on RLS signal of C-rich ssDNA-Ag NCs. As the concentration of Cu2+ ions increased, the RLS signal of C-rich ssDNA-Ag NCs gradually enhanced. The present method achieves the detection of Cu2+ ions in a linear range of 5 × 10-9 M to 7.5 × 10-7 M with a detection limit of 2 nM. Moreover, RLS spectrum, TEM image, fluorescence spectrum, X-ray photoelectron spectroscopy (XPS), and MALDI-TOF mass spectrometry were carried out for investigating the mechanism of the biosensor. The present strategy of constructing a biosensor based on AGR of metal nanoclusters paves a new way to design novel RLS probes.

Spectral Tuning of Plasmon Resonance in a Core/Shell (Au)Ag Nanocomposite

A bimetallic (Au)Ag nanocomposite with a core/shell structure was synthesized in aqueous solution and a H2O/EtOH mixture (1:1) containing polymers (carboxymethylcellulose, sodium polystyrenesulfonate, polyvinylpyrrolidone, dextran). Its structure and optical properties were characterized. The shape and position of scattering bands of colloidal noble-metal nanoparticles with optical density <0.1 were undistorted by solvent absorption. Scattering spectra had to be corrected for solutions of greater optical density. A method for correcting the resonant lightscattering spectra of Au and (Au)Ag nanoparticles was proposed for a single-beam apparatus. The possibility of surface plasmon resonance tuning for (Au)Ag with a short-wavelength shift of ~150 nm for the absorption band maximum and of ~84 nm for the resonant scattering band was demonstrated by varying the AgNO3 concentration during formation of the silver shell on the gold core.

Spectroscopic study of the interaction of insulin and its aptamer – sensitive optical detection of insulin

The binding of insulin to the insulin binding aptamer (IBA) was investigated with different spectroscopy techniques (UV/vis absorption, fluorescence, resonance light-scattering spectra (RLS), synchronous fluorescence, and three-dimensional fluorescence). The thermodynamic parameters (Kb, ΔH, ΔG, and ΔS) of the insulin–IBA complex were further investigated by temperature-dependent fluorescence measurement over the range of 25–37°C. The results of synchronous fluorescence, resonance light scattering (RLS) and three-dimensional fluorescence spectra showed that IBA would alter the structure of insulin. Folding of the dual-labeled insulin binding aptamer, FL-IBA, carrying 6-carboxyfluorescein (FAM) and 6-carboxytetramethylrhodamine (TAMRA) labels at termini of the insulin binding aptamer (IBA), into G-quadruplex leading to the contact quenching occurs as a result of the formation of a nonfluorescent complex between donor and acceptor. Significant fluorescent signal change when FL-IBA was bound to insulin is attributed to a conformational change in FL-IBA from a loose random coil to a compact G-quadruplex. Based on fluorescence quenching of IBA folding, a simple and sensitive insulin aptamer-based biosensor in the range of 2–70nM was proposed.

Determination of bismuth in pharmaceutical products by resonance light scattering using quaternary ammonium salts as molecular probe

Resonance light scattering (RLS) of bismuth-iodide-quaternary ammonium salts and their analytical application have been studied. Bismuth can react with a large excess of I− to form [BiI4]− in the presence of Tween-20; [BiI4]− further reacts with quaternary ammonium salts such as tetramethyl ammonium bromide (TMAB), tetrapropyl ammonium bromide (TPAB) and tetrabutyl ammonium bromide (TBAB) to form an ion-association compound. Moreover, the characteristics of RLS spectra of the complexes, the optimum conditions and the influencing factors have been investigated. The method has been applied to determine Bi(III) in pharmaceutical products with satisfactory results which are in agreement with that of atomic absorbance spectrometry (AAS).

Study of the interaction between bovine hemoglobin and analogs of biphenyldicarboxylate by spectrofluorimetry

The interaction between bovine hemoglobin and analogs of Biphenyldicarboxylate was investigated by fluorescence, synchronous fluorescence, ultraviolet–vis absorbance, resonance light-scattering spectra and three-dimensional fluorescence spectra at pH 7.40. The quenching mechanism and binding constants were determined by the quenching of bovine hemoglobin fluorescence in presence of analogs. Results showed that the nature of the quenching was of static type. Both the van der Waals and hydrogen bonding played a major role in stabilizing the complex. The distance between donor and acceptors was obtained to be 2.11–2.25nm according to Förster's theory. The influence of analogs on the conformation of bovine hemoglobin was investigated.

Study of Hybrid Photovoltaic Materials with Poly(3-Hexylthiophene) and CdS Nanoparticles by Spectroscopic Techniques

Poly (3-hexylthiophene) (P3HT) was synthesized via chemical oxidative reaction at room temperature with anhydrous ferric chloride as oxidant. The hybrid films of P3HT were prepared by doping inorganic semiconductor nanoparticles of CdS. Fourier transform infrared (FT-IR) spectrum, UV-vis, fluorescence and resonance light scattering (RLS) spectra were applied to characterize the photophysical properties of P3HT and doped polymer. The results indicated that the infrared absorbance of hybrid films increased with the increase of doped CdS content. The intensity of UV absorption presented a slight increase, the blend spectra were simply the sum of the absorptions of the constituent parts of the composite solution. With the addition of CdS nanoparticles, the emission peak of P3HT was shifted to longer wavelengths. The shift from 543 to 567 nm was due to the fluorescence resonance energy transfer between CdS nanoparticles and P3HT, and then the red-shift from 567 to 573 nm was caused by the agglomeration of CdS nanoparticles. RLS spectra revealed that the maximum scattering wavelength of systems initially showed a blue-shift, and then exhibited a pronounced red-shift with the addition of CdS nanoparticles. These findings provided insights into the role of spectroscopic techniques in studying the photophysical properties of composites. Our further work is toward investigating the mechanism and dynamic process of exciton interaction between polymers and inorganic semiconductor nanoparticles.

Comparative study of the interactions between ovalbumin and three alkaloids by spectrofluorimetry

The interaction between ovalbumin (OVA) and three purine alkaloids (caffeine, theophylline and diprophylline) was investigated by the aid of intrinsic and synchronous fluorescence, ultraviolet-vis absorbance, resonance light-scattering spectra and three-dimensional fluorescence spectra techniques. Results showed that the formation of complexes gave rise to the fluorescence quenching of OVA by caffeine, theophylline, and diprophylline. Static quenching was confirmed to results in the fluorescence quenching. The binding site number n, apparent binding constant KA and corresponding thermodynamic parameters were measured at different temperatures. The binding process was spontaneous molecular interaction procedures in which both enthalpy and Gibbs free energy decreased. Van der Waals forces and hydrogen bond played a major role in stabilizing the complex. The comparison between caffeine, theophylline, and diprophylline was made, and thermodynamic results showed that diprophylline was the strongest quencher and bound to OVA with the highest affinity among three compounds. The influence of molecular structure on the binding aspects was reported.

Investigations to reveal the nature of interactions of human hemoglobin with curcumin using optical techniques

Curcumin (CUR) is an important bioactive compound present in the rhizome of Curcuma longa. Herein, we report the interaction of CUR with human hemoglobin (Hb) using various biophysical methods viz., fluorescence, UV absorption, resonance light scattering spectra (RLS), synchronous fluorescence, fluorescence anisotropy, circular dichroism (CD) and three-dimensional fluorescence. There was a considerable quenching of the intrinsic fluorescence of Hb upon binding to CUR through dynamic quenching mechanism. The distance (r) between the donor and acceptor was obtained from the Forster's theory of fluorescence resonance energy transfer (FRET) and found to be 1.55nm. Alterations in the conformation of Hb due to its interaction with CUR were confirmed by UV absorption and CD spectroscopic methods. The α-helicity of Hb was found to decrease upon binding with CUR.

A label-free method for studying DNA sequence recognition of mitoxantrone based on resonance light-scattering technique

A label-free method for studying DNA sequence recognition of mitoxantrone (MIT) by resonance light-scattering (RLS) technique has been developed in this contribution. Through the RLS spectra, the selective no-covalent interactions between MIT and double-stranded DNA, single-stranded DNA (ssDNA), oligonucleotides were systematically studied. The results of the experiments displayed that MIT had an obvious preference to ssDNA with the K (K(RLS)), 15.16 mmol mg(-1) and the number of binding sites (N), 8.68 × 10(-4) mmol mg(-1). Besides, it was found that MIT had a preference to sequences that were rich in guanine and cytosine bases with K(RLS), 17.29 l mmol(-1) and N, 1.19 × 10(-2) l mmol(-1). The recognition mechanisms were well discussed and by fluorescence method and atom force microscopy, the RLS technique was confirmed to be a reliable method in this study. Compared with other methods, what the RLS strategy displayed was the direct interaction between anticancer drugs and DNA in vitro without the influence of a foreign substance. Thus, it can be a simple, fast and label-free strategy for DNA sequence recognition studies of DNA-targeted anticancer drugs.

Probing the Binding of the Flavonoid Diosmetin to Human Serum Albumin by Multispectroscopic Techniques

The binding mechanism of molecular interaction between diosmetin and human serum albumin (HSA) in a pH 7.4 phosphate buffer was studied using atomic force microscopy (AFM) and various spectroscopic techniques including fluorescence, resonance light scattering (RLS), UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by diosmetin was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The RLS spectra and AFM images showed that the dimension of the individual HSA molecules were larger after interaction with diosmetin. The thermodynamic parameters, ΔH° and ΔS° were calculated to be -24.56 kJ mol(-1) and 14.67 J mol(-1) K(-1), respectively, suggesting that the binding of diosmtin to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies and denaturation experiments in the presence of urea indicated site I as the main binding site for diosmetin on HSA. The binding distance between diosmetin and HSA was determined to be 3.54 nm based on the Förster theory. Analysis of CD and FT-IR spectra demonstrated that HSA conformation was slightly altered in the presence of diosmetin.

Investigation of the toxic effect of a QDs heterojunction on the interactions between small molecules and plasma proteins by fluorescence and resonance light-scattering spectra

The effect of a ZnO#ZnS QDs heterojunction (O#SQDs) on the binding affinities of flavonoid glycosides for bovine serum albumin (BSA) was investigated. The fluorescence intensities of BSA decreased remarkably with increasing concentration of O#SQDs. The magnitudes of the binding constants of flavonoid glycosides for BSA in the presence of O#SQDs were in the range of 10(5)-10(7) L mol(-1), and the number of binding sites per BSA (n) was determined as 1.24 ± 0.17. O#SQDs increased the affinities of flavonoid glycosides for BSA by about 2.96% to 114.68% depending on their structures. O#SQDs in blood will enhance the transportation of flavonoid glycosidegs in blood and improve their pharmacology effects. From this point, O#SQDs are a perfect candidate for flavonoid glycosides delivery applications.

Label-free detection of target DNA sequence and single-base mismatch in hepatitis C virus corresponding to oligonucleotide by resonance light scattering technique

A highly sensitive assay to detect sequence-specific DNA by the resonance light scattering (RLS) technique has been developed based on the enhanced RLS intensities of the RLS spectra at 399.5 nm. It was found that Hoechst 33258, when bound to dsDNA and ssDNA in electrolyte solution, displayed different RLS signals. This encouraged us to perform a direct and unlabelled sequence-specific DNA assay. At optimal conditions, this RLS assay can detect complementary target DNA over a range of 4.0 × 10−9–3.8 × 10−7 mol L−1, and the limit of detection was around 1.7 × 10−9 mol L−1. Additionally, the results of experiments showed that different RLS signals reflected a different degree of mismatch between probe DNA and target DNA, and mismatched variants of target DNA with single-base difference can even be well discriminated. Herein, we moved the RLS technique one-step further toward sensitivity, rapidity, simplicity and non-toxicity. The RLS assay results were identified with a fluorescence method, fluorescence polarization assay and atomic force microscope measurement.

Resonant light-scattering spectra of molecules with double-well vibrational potentials

Introduction. Oscillators, the motion of which is determined by a potential with a single minimum for a molecule in both the ground and excited electronic states, are used as a model for the vibrational subsystem in the overwhelming majority of theoretical studies of Raman scattering (RS) of light by molecules. The success of the theory is due mainly to the fact that the overlap integrals for wave functions of oscillators for the ground and excited electronic states of the molecule that are required to derive expressions for the RS line intensity are used in the analytical form. However, many vibrational states of various molecules should be examined using models of oscillators characterized by a potential with two minima (double-well potential). For example, this refers to models describing the Jahn–Teller and Renner–Teller effects, the rotation dynamics of a fragment of an organic molecule around a single or double bond, and the states of a proton in an intra- or intermolecular hydrogen bond (H-bond). Exact expressions for the steady-state wave functions of a particle in a double-well potential have not been obtained in the analytical form. Therefore, approximate wave functions that were found by numerical solution of the corresponding Schrodinger equation with the sought wave functions represented as a linear combination of the eigenfunctions of a harmonic oscillator were used as the vibrational wave functions in one of the first theoretical studies [1] of RS of light by a molecule with a vibrational subsystem characterized by a double-well potential in the lower of two interacting electronic states taking into account Jahn–Teller and Renner–Teller effects. Superpositions of two harmonic oscillator functions, each of which belonged to one of the potential wells, were taken as the approximate vibrational wave functions in theoretical studies [2–4] of RS of light by a molecule with a vibrational subsystem, the motion of which was determined by a double-well potential in the ground electronic state also. Obviously such an examination has a very limited scope of application. Only qualitative conclusions about certain features of the RS process in molecules with double-well vibrational potentials were drawn. Moreover, knowledge of the rules for RS of light by molecules with a double-well potential for the examined vibrational mode is of purely theoretical and great practical interest because RS spectroscopy, especially for irradiation of molecules in the frequency range of their self-absorption [resonance RS spectroscopy (RRS)], is an effective method for establishing, e.g., the mechanism of the position change of a proton in an intramolecular H-bond in the excited electronic state of the molecule during light transformation by it (proton phototransfer). Much attention has re