Shaopu Liu

Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion.

A novel fluorescent probe for Cu(2+) determination based on the fluorescence quenching of glyphosate (Glyp)-functionalized quantum dots (QDs) was firstly reported. Glyp had been used to modify the surface of QDs to form Glyp-functionalized QDs following the capping of thioglycolic acid on the core-shell CdTe/CdS QDs. Under the optimal conditions, the response was linearly proportional to the concentration of Cu(2+) between 2.4×10(-2)μg mL(-1) and 28μg mL(-1), with a detection limit of 1.3×10(-3)μg mL(-1) (3δ). The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu(2+). The fluorescent probe was successfully used for the determination of Cu(2+) in environmental samples. The mechanism of reaction was also discussed.

Resonance Rayleigh scattering spectra of ion-association nanoparticles of [Co(4-[(5-Chloro-2-pyridyl) azo]-1, 3-diaminobenzene)2]2+-sodium dodecyl benzene sulfonate system and its analytical application

In pH 1.8-3.0 Britton-Robinson (BR) buffer solution, cobalt (II) reacts with 4-[(5-Chloro-2-pyridyl) azo]-1, 3-diaminobenzene (5-Cl-PADAB, L) to form a cationic chelate [CoL(2)](2+). When interacting with anionic surfactants (AS) such as sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS) or sodium dodecyl sulfonate (SLS), the chelate can only react with SDBS to form ternary ion-association complexes ([CoL(2)][SDBS](2)). By virtue of the extrusion action of water and Van der Waals force, the hydrophobic ion-association complexes draw close to each other and further aggregate to form {[CoL(2)][SDBS](2)}(n) nanoparticles with an average diameter of 30 nm. As a result, resonance Rayleigh scattering (RRS) is enhanced greatly and new RRS spectra appear. Under the same conditions, both SDS and SLS exhibit no similar reactions and do not result in obvious change of RRS. Therefore, SDBS can be determined selectively by RRS method in the presence of SDS or SLS. The wavelength of 516 nm was chosen as a detection wavelength, the linear range and the detection limit (3sigma) are 0.05-6.0 microg mL(-1) and 0.015 microg mL(-1) for the determination of SDBS, respectively. The characteristics of RRS spectra of the [CoL(2)](2+)-SDBS system, the optimum conditions of the reaction and the influencing factors have been investigated. The effects of coexisting substances have been examined too, indicating a good selectivity of the method for the determination of SDBS. The method can be used for the determination of SDBS in waste water and river water samples, and the results are satisfactory compared with those of standard samples of SDBS. Based on the formation of {[CoL(2)][SDBS](2)}(n) nanoparticles, a sensitive, simple and rapid method has been developed for the determination of SDBS in environmental water samples using a RRS technique. Moreover, the reaction mechanism was discussed.

Study on the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra of the interactions of palladium(II)–ceftriaxone chelate with anionic surfactants and their analytical applications

In pH 1.8-2.9 Britton-Robinson (BR) buffer medium, ceftriaxone (CTRX) can react with palladium(II) (Pd(II)) to form 1:2 cationic chelate, which can further react with anionic surfactants (AS) such as sodium lauryl sulfonate (SLS), sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) to form 1:3 ion-association complexes. As a result, the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) were enhanced greatly. The maximum RRS, SOS and FDS wavelengths of three ion-association complexes were located at 335 nm, 560 nm and 390 nm, respectively. The increments of scattering intensity (DeltaI) were directly proportional to the concentrations of CTRX in certain ranges. The detection limits (3sigma) of CTRX for SLS, SDBS and SDS systems were 1.8 ng ml(-1), 2.3 ng ml(-1) and 2.3 ng ml(-1) (RRS method), 4.9 ng ml(-1), 7.4 ng ml(-1) and 4.7 ng ml(-1) (SOS method) and 6.8 ng ml(-1), 7.3 ng ml(-1) and 9.1 ng ml(-1) (FDS method), separately. The sensitivity of RRS method was higher than those of SOS and FDS methods. The optimum conditions of RRS method and the influence factors were investigated, and the composition of ion-association complexes and the reaction mechanism were discussed also. The effects of foreign substances were tested and it showed that the method has a good selectivity. Based on the ion-association reaction, the sensitive, simple and rapid methods for the determination of CTRX have been developed.

Resonance Rayleigh scattering spectra, non-linear scattering spectra of tetracaine hydrochloride–erythrosin system and its analytical application

The interaction between erythrosine (ET) and tetracaine hydrochloride (TA) was studied by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second-order scattering (SOS) combining with absorption spectrum. In a weak acidic medium of Britton-Robinson (BR) buffer solution of pH 4.5, erythrosine reacted with tetracaine hydrochloride to form 1:1 ion-association complex. As a result, the new spectra of RRS, SOS and FDS appeared and their intensities enhanced greatly. The maximum peaks of RRS, SOS and FDS were at 342 nm, 680 nm and 380 nm, respectively. The intensities of the three scattering were directly proportional to the concentration of TA in the range of 0.008-4.2 microg mL(-1) for RRS, 0.027-4.2 microg mL(-1) for SOS and 0.041-4.2 microg mL(-1) for FDS. The methods had very high sensitivities and good selectivities, and the detection limits were 0.003 microg mL(-1) for RRS, 0.008 microg mL(-1) for SOS and 0.012 microg mL(-1) for FDS, respectively. Therefore, a new method was developed to determinate trace amounts of TA. The recovery for the determination of TA in blood serum and urine samples was between 97.0% and 103.8%. In this study, mean polarizability was calculated by AM1 quantum chemistry method. In addition, the reasons for the enhancement of scattering spectra and the energy transfer between absorption, fluorescence and RRS were discussed.

A study on the interaction of proteins with some heteropoly compounds and their analytical application by resonance Rayleigh scattering method

In the dilute sulfuric acid medium, the reactions of proteins with some heteropoly compounds (HPC) including some heteropoly acids (HPA) and their reducing products would result in the enhancement of resonance Rayleigh scattering (RRS) intensity and the appearance of the corresponding RRS spectra. Their maximum scattering peaks were all at 470nm, and there were four smaller peaks at 400, 510, 800 and 940nm, respectively. In a certain range, the concentrations of proteins were directly proportional to the enhanced intensities of RRS. The methods have high sensitivities, and the detection limits (DL) were in the range of 11.6-54.0ngml(-1) depending on different heteropoly compounds. Among these methods, the phosphato-antimo-molybdate heteropoly acid (PSbMoA) system was the most sensitive, and its detection limits (3sigma) were 11.6ngml(-1) for bovine serum albumin (BSA), 12.5ngml(-1) for human serum albumin (HSA), and 16.0ngml(-1) for alpha-chymotrypsin (alpha-Chy), separately. Taking the PSbMoA and its reducing product systems for example, the suitable reaction conditions, affecting factors as well as the influence of coexisting substance have been investigated. The method has fairly good selectivity, and could be applied to the determination of protein in synthetic samples and practical samples with satisfactory results. A new method for the determination of trace amounts of protein based on RRS technique has been developed.

Interaction of adenine with palladium chloride, determination of adenine via resonance Rayleigh scattering method.

In pH 1.7-3.5 acid medium, palladium chloride could react with adenine (A) to form a ternary complex of [PdCl(2)·A], which would self-aggregate to form uniformly dispersed nanoparticles-[PdCl(2)·A](n) with an average size of 42 nm through the squeezing effect of aqueous phase and van der Waals force. This resulted in an enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum wavelengths were located at 311 nm, 611 nm and 395 nm, respectively. The scattering intensities of the three methods were proportional to the concentration of adenine in certain ranges, and the detection limit of the most sensitive RRS method was 5.4×10(-9) mol L(-1) (0.73 ng mL(-1)). The experimental conditions were optimized and effects of coexisting substances were evaluated. The method showed excellent selectivity because a certain amount of other nucleobase, nucleoside or nucleotide would not influence the measurement. Accordingly, a novel rapid, convenient, sensitive and selective RRS method for determination of adenine was proposed and applied to detect adenine in tablet and hydrolyzates of ctDNA samples with satisfactory results. The shape of nanoparticles was characterized by atomic force microscopy. The reaction mechanism and the reasons for enhancement of scattering were discussed by infrared spectra, quantum chemical calculations and absorption spectroscopy.

Study on the interaction of CdTe quantum dots with coumaric acid and caffeic acid based on fluorescence reversible tune

This paper describes the synthesis of CdTe quantum dots (QDs) together capped by glutathione and thioglycolic acid (GSH and TGA) in aqueous solution. The narrow photoluminescence (fwhm ≤ 40 nm) CdTe QDs, whose emission spans most of the visible spectrum from green through red, has a quantum yield (QY) of 68% at room temperature. GSH/TGA-CdTe QDs are characterized by various experimental techniques such as optical absorption, photoluminescence and AFM measurements. Coumaric acid and caffeic acid is able to quench the fluorescence of GSH/TGA-CdTe QDs, and the fluorescence intensity is linearly proportional to the concentration of quenchers. The addition of bovine serum albumin (BSA) restores the fluorescence intensity of GSH/TGA-CdTe QDs-coumaric acid system and GSH/TGA-CdTe QDs-caffeic acid system. The fluorescence recovery was due to the interaction of BSA with coumaric acid and caffeic acid, leading to the freeing of the GSH/TGA-CdTe QDs. The fluorescence quenching mechanism of GSH/TGA-CdTe QDs was discussed. The binding constant and thermodynamics parameters of BSA-coumaric acid and BSA-caffeic acid during the binding process were calculated in the paper.

Resonance Rayleigh scattering, second-order scattering and frequency doubling scattering methods for the indirect determination of penicillin antibiotics based on the formation of Fe3[Fe(CN)6]2 nanoparticles.

Under the HCl solution and heating condition, penicillin antibiotics such as amoxicillin (AMO), ampicillin (AMP), sodium cloxacillin (CLO), sodium carbenicillin (CAR) and sodium benzylpenicillin (BEN) could react with Fe(III) to produce Fe(II) which further reacted with Fe(CN)(6)(3-) to form a Fe(3)[Fe(CN)(6)](2) complex. By virtue of hydrophobic force and Van der Waals force, the complex aggregated to form Fe(3)[Fe(CN)(6)](2) nanoparticles with an average diameter of 45 nm. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) and non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The increments of scattering intensity (DeltaI) were directly proportional to the concentrations of the antibiotics in a certain range. The detection limits for the five penicillin antibiotics were 2.9-6.1 ng ml(-1) for RRS method, 4.0-6.8 ng ml(-1) for SOS method and 7.4-16.2 ng ml(-1) for FDS method, respectively. Among them, the RRS method exhibited the highest sensitivity and the AMO system was more sensitive than other antibiotics systems. Based on the above researches, a new highly sensitive and simple method for the indirect determination of penicillin antibiotics has been developed. It can be applied to the determination of penicillin antibiotics in capsule, tablet, human serum and urine samples. In this work, the spectral characteristics of absorption, RRS, SOS and FDS spectra, the optimum conditions of the reaction and the influencing factors were investigated. In addition, the reaction mechanism was discussed.

A dual-wavelength overlapping resonance Rayleigh scattering method for the determination of chondroitin sulfate with nile blue sulfate.

A dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was developed to detect chondroitin sulfate (CS) with nile blue sulfate (NBS). At pH 3.0-4.0 Britton-Robinson (BR) buffer medium, CS interacted with NBS to form an ion-association complex. As a result, the new spectra of resonance Rayleigh scattering (RRS), second order scattering (SOS) and frequence doubling scattering (FDS) appeared and their intensities were enhanced greatly. Their maximum wavelengths were located at 303 nm (RRS), 362 nm (RRS), 588 nm (SOS) and 350 nm (FDS), respectively. The scattering intensities of the three methods were proportional to the concentration of CS in certain ranges. The methods had high sensitivity and the detection limits were between 1.5 and 7.1 ng mL(-1). The DWO-RRS method had the highest sensitivity with the detection limit being 1.5 ng mL(-1). The characteristics of the spectra and optimal reaction conditions of RRS method were investigated. The effects of coexistent substances on the determination of CS were evaluated. Owing to the high sensitivity, RRS method had been applied to the determination of CS in eye drops with satisfactory results. The recovery range was between 99.4% and 104.6% and the relative standard deviation (RSD) was between 0.4% and 0.8%. In addition, the reasons for RRS enhancement were discussed and the shape of ion-association complex was characterized by atomic force microscopy (AFM).

Studying the interaction between CdTe quantum dots and Nile blue by absorption, fluorescence and resonance Rayleigh scattering spectra.

Thioglycolic acid (TGA) capped CdTe quantum dots (QDs) with the diameter of 2-3nm were synthesized. The interaction between CdTe QDs and Nile blue (NB) was investigated by ultraviolet-visible (UV-vis) absorption, resonance Rayleigh scattering (RRS) and fluorescence spectroscopy. UV-vis absorption spectrum of CdTe QDs and NB obviously changed, showing that CdTe QDs could associate with NB to form a new complex. At pH 6.8, NB effectively quenched the fluorescence of CdTe QDs. It was proved that the fluorescence quenching of CdTe QDs by NB was mainly result of the formation of CdTe QDs-NB complex, electrostatic attraction and hydrophobic forces played a major role in stabilizing the complex. The binding molar ratio of CdTe QDs and NB was 5:1 by a mole-ratio method. The interaction between CdTe QDs and NB lead to the remarkable enhancement of RRS and the enchantments were in proportional to the concentration of NB in a certain range. The mechanism of the interaction between CdTe QDs and NB, reasons for the enhancement of RRS intensity were also discussed. The obtained results suggested the more satisfactory mechanism for the interaction between CdTe QDs and NB.