One-pot hydrothermal synthesis of Si-doped carbon quantum dots with up-conversion fluorescence as fluorescent probes for dual-readout detection of berberine hydrochloride.

Here, the high fluorescent silicon-doped carbon quantum dots (Si-CQDs) were prepared by a facile and one-pot hydrothermal assay using 3-aminopropyltrimethoxysilane as the carbon and silicon source. The prepared Si-CQDs exhibit favorable water-soluble, high-temperature resistance, acid resistance, alkali resistance, high ionic strength resistance, high photostability, film-forming ability and solid-state fluorescence. Compared to other Si-CQDs that have been reported, the prepared Si-CQDs show unique up-conversion fluorescence. Furthermore, it is found that berberine hydrochloride (BH) can effectively quench the down- and up-conversion fluorescence of the Si-CQDs, making it can be used as a highly sensitive and specific probe for BH dual-mode sensing. Meanwhile, the linear range of down-conversion fluorescence detection for BH is 0.5-30.0 µmol/L with a limit of detection (LOD) of 50 nmol/L, and the linear range of up-conversion fluorescence assay for BH is 0-25.0 µmol/L. The mechanism of down-conversion fluorescence quenching by BH was investigated through a series of studies. The results show the quenching mechanism is the inner filter effect (IFE). Moreover, this proposed strategy has been well used to analyze BH in urine samples with satisfactory results.

A highly fluorescent lanthanide metal-organic framework as dual-mode visual sensor for berberine hydrochloride and tetracycline.

A microscale highly fluorescent Eu metal-organic framework (Eu-MOF) was synthesized with terephthalic acid and 1H-1,2,4-triazole-3,5-diamine by one-pot hydrothermal method. And it was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, powder X-ray diffraction, fluorescence spectroscopy, thermogravimetric analysis, and energy dispersive X-ray mapping. The prepared Eu-MOF has high quantum yield of 30.99%, excellent water dispersibility, good fluorescence stability, and favorable thermal stability. Based on the distinctly different fluorescence responses of different emission, the prepared Eu-MOF was used as dual-mode visual sensor for the sensitive detection of berberine hydrochloride and tetracycline. The limits of detection are 78 nM and 17 nM, respectively. The sensing mechanism was also discussed. Moreover, a filter paper sensor has been designed for sensing tetracycline with a notable fluorescence color change from blue to red. The prepared Eu-MOF is promising to be developed as a multi-mode luminescent sensor for visual detection in biochemical analysis. Graphical abstract Illustration of the synthesis of Eu-MOF and its sensing applications for berberine hydrochloride and tetracycline.

Synthesis of the Cu-Doped Dual-Emission Fluorescent Carbon Dots and Its Analytical Application.

New Cu-doped dual-emission carbon dots (D-CDs) were synthesized rapidly and simply via a one-pot solvothermal method, and its special photoluminescence mechanism was studied. D-CDs have two fluorescence (FL) emission peaks under one-wavelength excitation and can be used as dual-signal sensor which is usually designed with two or more substances. The prepared CDs show excellent water solubility, photostability, salt tolerance, oxidation resistance, and special optical properties. The raw material ratio, solvent, pH, time, and synthesis temperature were optimized. The characterizations of CDs including transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopic analysis, X-ray diffraction assignation of phases, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, FL spectrum, and ultraviolet-visible spectrum (UV-vis) were conducted. The investigation on mechanism indicates that the unique dual-emissive property is mainly caused by the energy-level gaps generated by the surface defects of CDs. The prepared D-CDs have good potential in dual-signal analysis and visualization sensing. To demonstrate the practical application, ferric ions, vitamin A acetate, and pH have been determined successfully.

One-Pot Hydrothermal Synthesis of Carbon Dots with Efficient Up- and Down-Converted Photoluminescence for the Sensitive Detection of Morin in a Dual-Readout Assay.

Blue luminescent carbon dots (CDs) with a high photoluminescence (PL) quantum yield (48.3 ± 5.3%) were prepared by the one-pot hydrothermal reaction of citric acid with poly(ethylenimine) (PEI). The CDs display bright PL, narrow emission spectra, pH-dependent PL intensity, high photostability, and up-converted luminescence. The CDs exhibit a quenching of both down- and up-conversion PL in the presence of morin and thus serve as useful probes for morin detection. Both down- and up-conversion measurements allow the quantification of concentrations from 0 to 300 µmol/L with a detection limit of 0.6 µmol/L, and this dual-mode detection increases the reliability of the measurement. The proposed method of determination is simple, sensitive, and cost-effective, with potential applications in clinical and biochemical assays.

High Sensitive and Selective Detection of PFOS with Resonance Light Scattering Technology Based on the Interaction with Victoria Blue B.

This report presents a simple, sensitive and selective victoria blue B (VBB)-based resonance light scattering (RLS) assay of perfluorooctane sulfonate (PFOS). In pH 6.0 KH2PO4-NaOH buffer solution, VBB can be protonated and reacts with PFOS through electrostatic interactions to produce ionic-association complexes. Simultaneously, the interaction leads to enhanced resonance light scattering intensities greatly, which are characterized with a peak at 277 nm. It is found that the enhanced RLS intensity is proportional to the concentration of PFOS in a range of 0.05 to 4.0 µmol·L-1. The limit of detection is 5.0 nmol·L-1. While, under the optimal experimental conditions, almost no change of the resonance light scattering intensity was observed between VBB and perfluorooctane acid (PFOA) which is one kind of representative perfluorinated compounds (PFCs). The excellent selectivity of PFOS could be due to the hydrophobicity of PFOS higher than PFOA. It is worth noting that the proposed method is capable of differentiating PFOS and some other PFCs. UV/Vis absorption spectrum and scanning electron microscope (SEM) image both were investigated to further validate the reaction mechanism. The interference of coexisting foreign substances and the optimum tests of reaction conditions, including pH value, reaction time, experimental temperature and ionic strength, were also investigated. This method has been successfully applied to the determination of PFOS in environmental water samples with RSD ≤1.74%. The experimental process as followed: In 2 mL colorimetric tube, 200 µL pH 6.0 KH2PO4-NaOH buffer solution, followed by adding 600 µL 20 µmol·L-1 VBB solution, swirl evenly, then add the right amount of PFOS solution. After vortex mixing with ultrapure water volume to 2 mL, swirl to mix, stand for 10 min at room temperature. Then the mixture was transferred for RLS measurements and absorption measurement.

[Colorimetric assay of perfluorooctanesulfonate based on gold nanoparticles].

For the property of persistent, bioaccumulation and genetic toxicity, perfluorooctanesulfonate (PFOS) is classified as a sort of persistent organic pollutants (POPs). It is significant to develop a novel assay for the determination of PFOS. In this work, we create a new colorimetric assay for PFOS in which the positively-charged gold nanoparticles (AuNPs) work as a nano-probe. This method works on the aggregation of AuNPs induced by PFOS via electrostatic interaction. The stable monodisperse AuNPs coated by cysteamine present color of red wine and the addition of PFOS can make the monodispersed AuNPs aggregated resulting in the color change from wine red to reddish purple with a red-shift in ultraviolet-visible absorption spectrum. The experimental results show that AuNPs has a characteristic absorption peak (524 nm), as well as a wide absorption peak (650 nm) and the absorption signal intensity is proportional to the PFOS content in a range of 0. 8-8. 0 µmo .l L-1. According to these, we developed a method based on ultraviolet-visible absorption and colorimetric to detect PFOS with the detection limit of 80 nmol . L-1. The scanning electron microscope (SEM) was investigated and the photos show that the stable AuNPs are made and the degree of AuNPs aggregation is related with PFOS concentration. The effect tests of coexisting substances in system show that common anions had less impact on the system and inorganic metal ions had some interference, which can be get rid of by cat- ion exchange resin in real sample. This assay was applied to detect PFOS in tap water with a recovery range of 87. 5%-118% and RSD 4. 4%. It is a novel application of AuNPs-based probe for PFOS detection. The proposed method has more advantages such as rapidity, low-cost and simplicity than conventional ones. In addition, it has the visual sensing function and the difference of color can be sensed by naked eyes directly, which produce ideas of real-time colorimetric strategies of nanoprobe application in environmental pollutant detection.

[Gold nanoparticles-based localized surface plasmon resonance scattering analysis method for the determination of trace amounts of Hg(II)].

Heavy-metal ions pose severe risks for human health and the environment. In particular, mercury-based pollutants are of great environmental concern because of the high toxicity of many Hg compounds. It is important to monitor the levels of potentially toxic metal Hg(II) in aquatic ecosystems. Gold nanoparticles (AuNPs) as nanomaterials have been generally studied. It is because their unique electrical, chemical, optical, and catalytic properties, AuNPs have caused widespread interest for applications in biological and chemical analysis and detection. In the present work, the authors took advantage of the aggregation-induced localized surface plasmon resonance (LSPR) light scattering signal change of sodium thioglycolate functionalized AuNPs in aqueous solutions to develop a highly efficient optical sensor for Hg(II). The as-modified AuNPs demonstrate that high negative charge densities exist on their surfaces at pH 9.0 Britton-Robinson (BR) buffer solution. The AuNPs occur aggregate in solution through chelation in the presence of Hg(II). The scanning electron microscope (SEM) images for the AuNPs display typical shapes of these AuNPs as regular and almost individual spherical particles. The color change of the AuNPs solution was induced by the addition of Hg(II) and it immediately changed from red to purple due to the aggregation. Under optimum conditions, a good linear relationship was obtained from 0.08 to 0.8 µmol x L(-1) with a correlation coefficient of 0.997 6, and the limit of detection (LOD) was 8.0 nmol x L(-1). PEG20000 was employed as a system stabilizer. The proposed method has an excellent selectivity for Hg(II) in aqueous medium over other metal ions. The optimum test of reaction conditions, including the amount of AuNPs, pH value, reaction stability and ionic strength, were also investigated. This method has been used for determination of Hg(II) successfully in environmental water sample. This approach manifested several advantages including short analysis time, high sensitivity, low cost, excellent selectivity and ease of operation.

Observable temperature-dependent compaction-decompaction of cationic polythiophene in the presence of iodide.

Investigation on compaction and decompaction of polymers is very important since it is a fundamental problem in polymer physics. With the aids of atomic force microscope (AFM) and dynamic light scattering (DLS) measurements in this contribution, the temperature-dependent compaction/decompaction transition process of water-soluble cationic polythiophene (PT) was investigated in the presence of KI. The above process is characterized by the red-to-yellow color change and fluorescence recovery and is reversible during the heating-cooling cycles in the range from 25 to 55 °C, indicating that the compaction and decompaction of polymer can be employed as a temperature indicator.

Highly selective light scattering imaging of chromium (III) in living cells with silver nanoparticles.

In this contribution, we present a highly selective chromium ion (Cr(3+))-induced aggregation of citrate-capped silver nanoparticles, which could be applied for the imaging of the distribution of Cr(3+) in cells. It was found that selective aggregation of citrate-capped silver nanoparticles occurs at room temperature in the presence of Cr(3+) in aqueous medium of pH 6.8, resulting in color change from yellow to pink in 10 min and enhanced localized surface plasmon resonance (LSPR) scattering signals. Tenfold of other metal ions including Al(3+), Ca(2+), Co(2+), Cu(2+), Fe(2+), Fe(3+), Hg(2+), La(3+), Mg(2+), Ni(2+), Pb(2+), Tb(3+) and Zn(2+) had no response. Mechanism analysis showed that the aggregation is mainly dependent on the chelation of Cr(3+) ion with the citrate ion capped on silver nanoparticles, forming crosslinking aggregates of silver nanoparticles. With the Cr(3+)-induced enhancement of LSPR scattering signals, Cr(3+) in cytoplasm of human bone marrow neuroblastoma cells could be imaged with dark-field light scattering imaging technique.

Determination of lead in environmental water by a backward light scattering technique.

An optical fiber assembly developed in our laboratory, which is based on detecting backward light scattering (BLS) signals, is now applied to detect the lead content in environmental samples. Due to effectively eliminating the interference of reflected light, this BLS signals based detection assembly can be used to determine analyte directly. In HAc-NaAc buffer medium (pH 4.8), the interaction of lead and sodium tetraphenylboron (TPB) in the presence of polyethylene glycol (PEG) yields large particles of ternary complex, resulting in strong enhanced backward light scattering (BLS) signals characterized at 371nm. By measuring the BLS signals with the homemade optical fiber assembly coupled with a common spectrofluorometer, we found that the enhanced BLS intensity is proportional to lead content over the range of 0.03-1.0mugml(-1) with the limit of determination (LOD) of 2.6ngml(-1). Three artificial water samples containing various coexistent substances were detected with the recovery of 90.1-107.5%. Standard addition method was used to detect the lead content in drink tap water, and found that the lead is hardly to detect due to too low content. Prior enrichment should be made in order to detect river water samples, and it was found that the content of lead in Jialing River at Bebei Dock is about 14ngml(-1), identical to the results using inductively coupled plasma atomic emission spectrometry (ICP-AES).

Pharmacokinetic detection of penicillin excreted in urine using a totally internally reflected resonance light scattering technique with cetyltrimethylammonium bromide.

A quantitative analysis method for penicillins including ampicillin (AmP), benzyl penicillin (BP), oxacillin (OA) and amoxycillin (AmO) is proposed that makes use of the totally internally reflected resonance light scattering (TIR-RLS) signal from the penicillin at the H2O/CCl4 interface in the presence of cetyltrimethylammonium bromide (CTMAB), and enables the pharmacokinetics of penicillin taken orally and excreted through urine to be monitored. Penicillin is coadsorbed with CTMAB at the H2O/CCl4 interface in neutral solution, resulting in the formation of ion associates that display greatly enhanced TIR-RLS signals (maximum at 368-372 nm). This enhanced TIR-RLS intensity was found to be proportional to the penicillin concentration over the range 0.2 x 10(-6) to 2.2 x 10(-6) mol L(-1), with limits of determination (3sigma) of 5.0 x 10(-8) to 7.0 x 10(-8) mol L(-1). Pharmacokinetics studies performed using the present method show that the excretion of orally-taken ampicillin through urine has a half-time of 1.05 h and an excremental quantum over 8 h of 49.3%, respectively.