Second-order Scattering Intensities Research Articles

Physicochemically modulated fluorescence-scattering ratiometric sensor for selective and visual detection of levodopa

In this study, a facile fluorescence-scattering ratiometric sensor was designed for visual and selective detection of levodopa (LD) via a clever physicochemical modulation scheme. The alkalized products of LD can rapidly react with polyethyleneimine (PEI) to exhibit an intense blue fluorescence and decrease the second-order scattering (SOS) signal of PEI. As the concentration of LD increased, the fluorescence intensity at 420 nm increased and the SOS intensity at 675 nm decreased synchronously. Thus the fluorescence-scattering ratiometric sensor was constructed by virtue of the two simultaneously changed signals. Furthermore, red light-emitting Au nanoclusters (AuNCs) were added into the above mixture solution to enlarge the SOS signal and provide a stable red background fluorescence. The intensity ratio of fluorescence to SOS (F/(S/Sblank)) is linear dependent on CLD in the wide range of 50.0–––30000.0 nM, and LD as low as 50.0 nM can be identified with the naked eye via change of fluorescence color. The developed ratiometric sensor is smart, simple and efficient, and has been applied to the convenient assay of LD in real samples. The proposed physicochemical modulation strategy provides a new and facile path for selectively and visually identifying the target from its analogues.

Second-Order Scattering Quenching in Fluorescence Spectra of Natural Humates as a Tracer of Formation Stable Supramolecular System for the Delivery of Poorly Soluble Antiviral Drugs on the Example of Mangiferin and Favipiravir.

In the present work, the methods of dynamic light scattering and fluorescence spectroscopy were applied to study the optical properties of aqueous dilutions of the humic substances complex (HC) as a potential drug delivery system. The supramolecular structures in the humate solution were characterized as monodisperse systems of the submicron range with a tendency to decrease in particle size with a decrease in the dry matter concentration. The slightly alkaline medium (8.3) of the studied aqueous dilutions of HC causes the absence of a pronounced fluorescence maximum in the region from 400 to 500 nm. However, the presence of an analytically significant, inversely proportional to the concentration second-order scattering (SOS) signal at 2λex = λem was shown. In the examples of the antiviral substances mangiferin and favipiravir, it was shown that the use of the humic complex as a drug carrier makes it possible to increase the solubility by several times and simultaneously obtain a system with a smaller particle size of the dispersed phase. It has been shown that HC can interact with mangiferin and favipiravir to form stable structures, which lead to a significant decrease in SOS intensities on HC SOS spectra. The scattering wavelengths, λex/λem, were registered at 350 nm/750 nm for mangiferin and 365 nm/730 nm for favipiravir, respectively. The increments of the scattering intensities (I0/I) turned out to be proportional to the concentration of antiviral components in a certain range of concentrations.

Sensitive determination of tobramycin using homocystine capped gold nanoclusters as probe by second-order scattering

A novel photoluminescent Hcy-AuNCs has been developed through one-pot reduction method, to establish a tobramycin sensing by second-order scattering (SOS). Hcy-AuNCs could spontaneously assemble to small-scaled aggregation, resulting in remarkable intensity enhancement of scattered luminescence signals. The luminescence of Hcy-AuNCs could be clearly observed under ultraviolet lamp, when excited at 365 nm, a significant luminescent intensity at 741 nm was monitored in SOS spectra. The introduction of AuNPs would cause large-scaled aggregation of Hcy-AuNCs that was rapidly settled in the solution, resulting in the decrease of SOS intensity. Besides, the non-radiative energy transfer between AuNPs and Hcy-AuNCs would also reduce the luminescent intensity. However, the addition of tobramycin would cause the aggregation of AuNPs due to the electrostatic and covalent bonding between AuNPs and tobramycin, thus eliminating the interference of AuNPs. The luminescence of Hcy-AuNCs reappeared, exhibiting an optical response toward tobramycin. The good linearity was obtained in a wide range from 4 nM to 300 nM with a low detection limit of 0.27 nM. The selectivity was acceptable toward different types of antibiotics. Finally, the proposed method was successfully applied to the widely used tobramycin eye drops.

Dual-Emitting N/S-Doped Carbon Dots-Based Ratiometric Fluorescent and Light Scattering Sensor for High Precision Detection of Fe(III) Ions.

Precise and rapid sensing of Fe(III) under concerned facile conditions is important in environmental monitoring. Herein, a facile and label-free ratiometric sensor is constructed for selective determination of Fe(III) ions by coupling second-order scattering (SOS) and fluorescence. We were synthesized fluorescent N, S-doped carbon dots (N/S-CDs) via facile one-step hydrothermal treatment with an intensive fluorescence and a weak SOS signal and high quantum yield (32%). The fluorescence of N/S-CDs was quenched whereas the intensity of SOS was relatively increased by Fe(III) ions due to aggregation-induced fluorescence quenching or enhancement. Based on this effect, a novel fluorescent ratiometric probe with the combined fluorescence and SOS is proposed for the sensing of Fe(III) ions, and with the detection limit of 83nM and linear range of 0.1-10μM and 10-40μM, respectively.

A ratiometric fluorescence-scattered light strategy based on MoS2 quantum dots/CoOOH nanoflakes system for ascorbic acid detection

A facile ratiometric fluorescence method for ascorbic acid (AA) detection was established by combining the fluorescence of MoS2 quantum dots (QDs) with second-order scattering (SOS) of CoOOH. In MoS2 QDs/CoOOH nanohybrid system, the fluorescence of MoS2 QDs was quenched by CoOOH whereas the intensity of SOS was relatively close to the fluorescence due to the intrinsic high scattering ability of large size CoOOH nanoflakes. With the addition of AA, CoOOH nanoflakes were reduced to Co2+ accompanied the size decline and the disappearance of characteristic absorption in UV–vis spectrum, resulting in the fluorescence recovery and SOS fading. Thus, the ratiometric detection of AA was obtained through the opposite changes of fluorescence and SOS. Under optimized conditions, the detection limit of AA was 0.21 μmol L−1 with a linear range from 0.80 to 32.0 μmol L−1. Furthermore, the MoS2 QDs/CoOOH nanohybrid system was applied to the detection of AA in human serum samples and vitamin C tablets with satisfactory results.

Study of silver nanoparticles sensitized fluorescence and second-order scattering of terbium(III)-pefloxacin mesylate complex and determination of pefloxacin mesylate.

α-Keto acid of pefloxacin mesylate (PFLX) can form the complex with Terbium(III). The intramolecular energy from PFLX to Terbium(III) ion takes place when excited, and thus Terbium(III) excited state is formed and then emits the characteristic fluorescence of Terbium(III), locating at 490, 545, 580, and 620 nm. The second-order scattering (SOS) peak at 545 nm also appears for the complex with the exciting wavelength of 273 nm. When the silver nanoparticles are added to the system, the luminescence intensity at 545 nm greatly increased. So, with the adding of nanoparticles to the Terbium(III)-PFLX complex, not only is the intramolecular energy promoted but also the SOS intensity is enhanced. The experimental results show that it is the silver nanoparticles with certain size and certain concentration which can greatly enhance the fluorescence-SOS intensity, and the relative intensity at 545 nm is proportional to the amount of PFLX. Based on this phenomenon, a novel method for the determination of PFLX has been developed and applied to the determination of PFLX in capsule and serum samples.

Abstracts of the 17th International Symposium on Bioluminescence and Chemiluminescence ‐ (ISBC 2012)

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Analytical Application of Resonance Rayleigh Scattering, Frequency Doubling Scattering, and Second-Order Scattering Spectra for the Sodium Alginate-CTAB System

Three new methods for the determination of trace amounts of sodium alginate (SA) based on the reaction of SA with cetyltrimethylammonium bromide (CTAB) by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS), and second-order scattering (SOS) have been investigated. The SA can react with CTAB in a pH 10.0 Britton–Robinson buffer to form a new product, which can lead to a significant enhancement of RRS, FDS, and SOS intensities and appearance of new spectra. The maximum scattering wavelengths, λex/λem, appear at 351 nm/351 nm for RRS, 240 nm/480 nm for SOS, and 870 nm/435 nm for FDS, respectively. The increments of the scattering intensities (ΔI) are proportional to the concentration of SA in a certain range. The detection limits (3σ) for SA are 3.69 ng mL−1 for the RRS method, 6.91 ng mL−1 for the FDS method, and 7.45 ng mL−1 for the SOS method under optimum conditions. The proposed methods were applied to the determination of SA in real samples with satisfactory results.

Resonance light scattering method for the determination of anionic surfactant with acridine orange

The resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency-double scattering (FDS) spectra of sodium dodecylbenzene sulfonate (SDBS) (anionic surfactant (AS)) with acridine orange (AO) system were studied. Experimental results showed that when λ em = λ ex = 537 nm, the RRS peak of AO was greatly enhanced with the increase of SDBS concentration at a pH range of 1.8–4.0. The linear range of the calibration curve for SDBS was 0.028–8.71 mg L −1 with a detection limit of 8.36 μg L −1 when the AO concentration was 2.5 × 10 −5mol L −1. The method has been applied to the determination of trace amount of AS in environmental water samples with satisfactory results. In addition, when λ em = 321 nm and λ ex = 642 nm, the intensity of FDS was proportional to the SDBS concentration ranging from 0.014 to 8.71 mg L −1 and the correlation coefficient was 0.993 with a detection limit of 4.31 μg L −1; when λ em = 642 nm and λ ex = 321 nm, the intensity of SOS was proportional to the SDBS concentration ranging from 0.050 to 8.71 mg L −1, and the correlation coefficient was 0.993 with a detection limit of 14.9 μg L −1.

The Second-order Scattering of the Interaction of Pd Nanoparticles with Protein and Its Analytical Application

The second-order scattering (SOS) phenomenon of the interaction of Pd nanoparticles with protein was reported and a simple, sensitive, palladium nanoparticle-based assay for trace amount of protein with SOS technique was developed. The SOS intensities were significantly enhanced due to the interaction of Pd nanoparticles with bovine serum albumin (BSA) or human serum albumin (HSA) at pH 3.5 or 4.0, respectively. The maximum SOS peak appeared at 260/520 nm (λ ex /λ em ). The optimal experiment conditions, affecting factors and the influence of some coexisting substances were checked. The SOS intensity increased proportionally with the increase of Pd concentration below 3.0 × 10 -5 mol·L -1 , while declined gradually above 4.0 × 10 -5 mol·L -1 . BSA within the range of 0.01-2.6 μg·mL -1 and HSA of 0.01-1.7 μg·mL -1 can be detected with this method and the detection limits were 2.3 and 11.2 ng·mL -1 , respectively. The method was successfully applied to the quantitative detection of total protein content in human serum samples with the maximum relative standard deviation (RSD) lower than 2.6% and the recoveries over the range of 99.5-100.5%.

A study on silver nanoparticles-sensitized fluorescence and second-order scattering of the complexes of Tb(III) with ciprofloxacin and its applications

Fluorescence of terbium(III) is sensitized when excited in the presence of ciprofloxacin (CPLX) in the aqueous solution because a Tb(III)–CPLX complex is formed and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)–CPLX complexes with the excitation wavelength of 272 nm. The intensity at 545 nm obviously increases when the silver nanoparticles are added to the Tb(III)–CPLX system, and the relative intensity is proportional to the concentration of CPLX. Based on this phenomenon, a new method for the determination of CPLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The intensity is enhanced most by silver nanoparticles at pH 6.0. The calibration graph for CPLX is linear in the range of 3.0 × 10 −9 to 1.0 × 10 −5 mol l −1. The detection limit is 8.5 × 10 −10 mol l −1. The method was applied satisfactorily to the determination of CPLX in tablets and capsules. The results show that silver nanoparticles with certain size and concentration can enhance the fluorescence and SOS intensity of the system.

Study of the influence of silver nanoparticles on the second-order scattering and the fluorescence of the complexes of Tb(III) with quinolones and determination of the quinolones

Quinolones (Qs) can form the complex with Tb(III) ion, and the intramolecular energy transfer from Qs to Tb(III) takes place when excited. And thus the characteristic fluorescence of Tb(III) ion was enhanced and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)–Qs complexes with the exciting wavelength of 274 nm. When the silver nanoparticles were added to the Tb(III)–Qs system, the luminescence intensity at 545 nm greatly increased. And the relative intensity is proportional to the amount of Qs. Based on this phenomenon, a novel method for determination of quinolones has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The luminescence intensity is greatly enhanced by silver nanoparticles in the pH range 5.5–6.2. The calibration graphs for pipemidic acid (PPA) and lomefloxacin (LMFX) are linear in the range 2.0 × 10 −10 to 1.0 × 10 −5 and 1.0 × 10 −9 to 1.0 × 10 −5 mol L −1, respectively. The limits of detection are 4.7 × 10 −11 mol L −1 for PPA and 1.1 × 10 −10 mol L −1 for LMFX. The method was applied satisfactorily to the determination of the two quinolones (Qs) in tablet, capsule, urine and serum samples. The experimental results showed that it is the certain size and certain concentration of silver nanoparticles that can greatly enhance the fluorescence -SOS intensity.

Study of the interaction of nucleic acid with europium(III) and CTMAB and determination of nucleic acids at nanogram levels by the second-order scattering

This paper firstly reports the second-order scattering (SOS) phenomenon in the nucleic acid system using a common spectrofluorometer. And a novel determination method of nucleic acids at nanogram level has been developed. Studies involving calf thymus DNA (ctDNA), fish sperm DNA (fsDNA) and yeast RNA (yRNA) showed that the SOS intensity of nucleic acids can be enhanced by La 3+, Ce 3+, Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ ion, of which Eu 3+ ion has the largest enhancement. And the intensity of the SOS is proportional to the concentration of nucleic acids. Maximum SOS peak at 550 nm appeared at pH 7.5 and 6.0 × 10 −5 mol l −1 CTMAB (cetyltrimethylammonium bromide). Under the optimal conditions, the calibration graphs were linear in the range of 1.0 × 10 −8 to 4.0 × 10 −5 g ml −1 for ctDNA, 6.0 × 10 −9 to 2.0 × 10 −6 g ml −1 for fsDNA, and 8.0 × 10 −9 to 1.0 × 10 −6 g ml −1 for yRNA, respectively. The detection limits were 1.7 ng ml −1 for ctDNA, 0.36 ng ml −1 for fsDNA and 0.21 ng ml −1 for yRNA, respectively. In comparison with most other methods for the determination of nucleic acids, this method is more convenient, more sensitive and simpler. And the possible mechanism was proposed.

Frequency doubling scattering and second-order scattering technology as novel methods for the determination of the inclusion constant of procaine hydrochloride to β-cyclodextrin

The frequency doubling scattering (FDS) and second-order scattering (SOS) intensities of procaine hydrochloride solution were weak. When β-cyclodextrin was added to the procaine hydrochloride solution, it can form a 1:1 inclusion complex with procaine hydrochloride established by spectrophotometry, and the FDS and SOS intensities were enhanced greatly. Their maximum scattering wavelengths appeared at 390 nm for FDS and 480 nm for SOS, respectively. The intensities of FDS and SOS at their maximum scattering wavelengths increased with an increase in β-cyclodextrin concentration. Based on this fact, the FDS and SOS methods were first applied to the determination of the inclusion constant of procaine hydrochloride to β-cyclodextrin. The inclusion constant, K f, of the procaine hydrochloride–β-cyclodextrin complex were 1.11×10 2−1.19×10 2 l mol −1 for the FDS and SOS methods. To compare with these methods, the spectrophotometric and fluorescence experiments have been done with satisfactory results.