Zhongfang Liu

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.

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).

Fluorescence quenching method for the determination of bleomycins A5 and A2 with halofluorescein dyes

In weak acidic medium, the anticancer antibiotics bleomycin A5 (BLMA5) and bleomycin A2 (BLMA2) bind with halofluorescein dyes, such as erythrosin (Ery), eosin Y (EY) and eosin B (EB), to form ion-association complexes, which causes fluorescence quenching of halofluorescein dyes. The quenching values (DeltaF) are directly in proportional to the concentrations of bleomycins over the range 0.09-2.5 microg/mL. Based on this, a fluorescence quenching method for the determination of BLMA5 and BLMA2 has been developed. The dynamic range is 0.12-2.5 microg/mL for the determination of BLMA5 and 0.09-2.0 microg/mL for BLMA2, with detection limits (3sigma) of 0.04 microg/mL for BLMA5, 0.03 microg/mL for BLMA2, respectively. It has been applied to determine the two antibiotics in human serum, urine and rabbit serum samples. The recovery is in the range 90-102%. In this work, the optimum reaction conditions and the spectral characteristics of the fluorescence are investigated. The reasons for fluorescence quenching are discussed, based on the fluorescence theory.

Determination of carbazochrome by fluorescence quenching method

A sensitive, simple and selective spectrofluorimetric method for the reaction of carbazochrome (CBZC) and Eosin Y (EY) or Phloxine B (PB) in acidic medium is developed for the determination of carbazochrome in biological fluids, which gives a highly fluorescent derivative measured at 545 and 565 nm at excitation wavelengths of 301 and 305 nm. The fluorescence quenching extent (ΔF) is proportional to the concentration of CBZC for CBZC-EY and CBZC-PB system at the range of 0.03-1.50 μg/mL and 0.08-1.25 μg/mL, respectively. The detection limit is 9.1 ng/mL for EY system and 22.7 ng/mL for PB system. The intra-day and inter-day reproducibility (RSD values) are less than 8.3% under three concentrations. Moreover, the affecting factors of fluorescence intensity of the product are carefully investigated and optimized, as well as the effect of coexisting substances. Judging from temperature, the Stern-Volmer plots and fluorescence emission decay curves, the quenching of fluorescence of EY and PB by CBZC is a static quenching process, caused by electrostatic attraction and aromatic stacking interaction.

Facile synthesis of fluorescent carbon dots for determination of curcumin based on fluorescence resonance energy transfer

In the present work, a novel sensing system based on fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and curcumin (Cur) was designed for Cur detection. CDs were synthesized via a facile one-pot pyrolysis treatment using diethylenetriaminepentaacetic acid (DTPA) as the carbon source. The as-prepared CDs possessed strong blue fluorescence and excitation wavelength-dependent emission behavior with the maximum excitation and emission wavelength at 360 nm and 420 nm, respectively. However, the fluorescence of the CDs quenched with the introduction of Cur via FRET and the decreased intensity was linearly proportional to the concentration of Cur in the range of 0.74–5.18 μg mL−1, leading to the quantitative detection of Cur with an excellent detection limit of 44.8 ng mL−1. Furthermore, the CD-based probe can be applied in the determination of Cur in real samples with satisfactory results. The proposed method is thus expected to become a potential tool for the fast response of Cur.