Ratiometric electrogenerated chemiluminescence sensing microRNA based on electrochemically controlled release of lucigenin from silica/chitosan/lucigenin nanoparticles.

The dye-doped silica nanoparticles-based electrogenerated chemiluminescence (ECL) has been widely explored for analytical purposes due to its high sensitivity, simplicity and wide dynamic concentration range. However, only a few of dye molecules located at the near surface of nanoparticles can participate in the ECL reaction due to the poor conductivity of silica nano-matrix. In addition, the ECL signal is easy to be affected by environmental interference, which results in poor accuracy. Herein, a ratiometric ECL sensing method is established based on the electrochemically controlled release of lucigenin molecules from silica/chitosan/lucigenin composite nanoparticles (Lu/CS NPs) with the aid of sulfide ions. Firstly, H+ produced from the electrochemical oxidation of HS- ions can combine with SiO- and displace lucigenin from Lu/CS NPs. The released lucigenin molecules react with the reactive oxygen species (ROS) generated from the electroreduction of dissolved oxygen to produce the cathodic ECL signal. In addition, the excited elemental sulfur from the electrooxidation of HS- ions transfers its energy to lucigenin molecules and makes them be excited to produce energy-transfer anodic ECL signal. Based on these findings, a ratiometric ECL sensor is developed taking the anodic ECL intensity of lucigenin as a reference signal for the cathodic ECL of lucigenin. The proposed ratiometric ECL sensor has been successfully applied to the detection of let-7a with a wide linear range of 0.1-9.0 pM, a low detection limit of 28 fM, high selectivity and good reproducibility. Moreover, the developed approach was used to detect let-7a in human serum composite samples with good recoveries.

Ratiometric fluorescence assay for sulfide ions with fluorescent MOF-based nanozyme.

A novel ratiometric fluorescence strategy for sulfide ions (S2-) analysis has been developed using metal-organic framework (MOF)-based nanozyme. NH2-Cu-MOF displays blue fluorescence (λem = 435 nm) originating from 2-amino-1,4-benzenedicarboxylic acid ligand. Besides, it possesses oxidase-like activity due to Cu2+ node, which can trigger chromogenic reaction. o-Phenylenediamine (OPD), as a common enzyme substrate, can be oxidized by NH2-Cu-MOF to form luminescent products (oxOPD) (λem = 570 nm). Inner filter effect occurs between oxOPD and MOF. Upon exposure to S2-, oxidase-like activity of MOF is depressed significantly because of the generation of CuS. On one hand, the amount of free Cu2+ decreases, affecting the yielding of oxOPD. On the other hand, CuNPs with larger size are obtained during the oxidation-reduction reaction between Cu2+ and OPD, which show weaker autocatalytic ability for OPD oxidation. These result in the decrease and increase of intensities at 570 and 435 nm, respectively. This method exhibits sensitive and selective responses towards S2- with LOD of 0.1 µM. Furthermore, such ratiometric strategy has been applied to detect S2- in food samples.

Removal of Sulfide Ions from Kraft Washing Effluents by Photocatalysis with N and Fe Codoped Carbon Dots.

N and Fe codoped carbon dots (N,Fe-CDs) were fabricated from citric acid, L-glutamic acid and ferric chloride via a hydrothermal method for the photocatalytic removal of S2- from kraft washing effluents (KWE). The N,Fe-CDs were fluorescent nanoparticles (average size of 3.18 nm) and catalyzed the oxidation of S2- following a first-order kinetic model with an activation energy of 33.77 kJ/mol. The N,Fe-CDs tolerated elevated temperatures as high as 80 °C without catalyst deactivation. The N,Fe-CDs catalysts were reusable for at least four cycles, preserving over 90% of the activity. In the treatment of KWE from the kraft pulping of eucalyptus, the concentration of S2- was decreased by the N,Fe-CDs from 1.19 to 0.41 mmol/L in 6 h. Consequently, near complete remediation was obtained in 24 h. In addition, half of the chemical oxygen demand was removed after treatment with 500 mg/L of the N,Fe-CDs. In addition, the present photocatalyst was safe within a concentration of 200 mg/L, as indicated by the acetylcholinesterase inhibition test. Our findings may help develop a cleaner production process for kraft brownstock washing.

One-step hydrothermal synthesis of fluorescent silicon nanoparticles for sensing sulfide ions and cell imaging.

We have presented a hydrothermal approach for synthesizing fluorescent silicon nanoparticles (F-SiNPs) with yellow-green emission. The obtained F-SiNPs exhibited excellent stability and good biocompatibility. By virtue of the specific reaction between S2- and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), colorimetric assay of S2- was realized with a good linear range of 0-100 µM. The colorimetric detection system could be further combined with F-SiNPs to construct a probe for fluorescence turn-off sensing S2- in aqueous solution due to inner filter effect. In the fluorescent detection system, a good linearity with S2- concentration in the range of 0-50 µM was accomplished. And as low as 0.1 µM S2- was successfully detected. Moreover, the F-SiNPs displayed low cytotoxicity and good biocompatibility, and was further utilized for cell imaging. These results demonstrated the promising applications of F-SiNPs in S2- analysis and bioimaging.

Sensitive detection of sulfide ions in red region based on luminescence resonance energy transfer between upconversion nanoparticles and dye-670.

Many sulfides are toxic substances that easily harm the respiratory tract, therefore affecting respiratory function or damaging other organs of the body, leading to its failure. Therefore, there is a pressing need to develop methods for sensitive detection of sulfur ions (S2- ). Based on luminescence resonance energy transfer (LRET) theory, we report the construction of a near-infrared (NIR) excitation luminescence probe using NaGdF4 :Yb3+ ,Er3+ @NaYF4 upconversion nanoparticles (UCNPs) as the donor and dye-670 as the receptor for detection of S2- . When UCNPs and dye-670 molecules were combined using ligand exchange and electrostatic attraction, LRET occurred and UCNP luminescence was quenched. When S2- was added to the system, sulfide ions were able to destroy the double bond of the dye, inhibiting LRET and restoring UCNP luminescence. Under optimum condition, the linear range of S2- detection was 0.65-18.2 µM, and the detection limit was 34.2 nM. This method was applied for determination of S2- in water with satisfactory results.

Functionalized Copper Nanoclusters-Based Fluorescent Probe with Aggregation-Induced Emission Property for Selective Detection of Sulfide Ions in Food Additives.

In this paper, a novel and facile synthetic method of 3-mercaptopropionic acid functionalized copper nanoclusters with aggregation-induced emission (AIE) induced by Cu2+ (Cu2+@MPA-Cu NCs) was developed by a one-pot reaction as a fluorescent probe for the detection of sulfide ion (S2-). The prepared Cu2+@MPA-Cu NCs behaved as aggregated clusters and had strong pink fluorescence under 365 nm UV light with excellent fluorescence emission at 610 nm. The quantum yield increased from 0.56% to 4.8% before and after Cu2+ added. The presence of S2- would strongly bind to Cu2+, which caused the structure of the aggregated Cu2+@MPA-Cu NCs to be destroyed and then the fluorescence quenched. On the basis of this principle, a fluorescent probe was constructed for the detection of S2- with a very good linearity in the range 0-600 µM (R2 = 0.9843) and a detection limit of 26.3 nM. Finally, the nanohybrids were successfully demonstrated for the application in the selective detection of S2- in food additives. This study essentially paved a new avenue for effectively developing an easy sensor platform for S2- measurements in food additives.

The use of high-performance liquid chromatography with diode array detector for the determination of sulfide ions in human urine samples using pyrylium salts.

Hydrogen sulfide is a toxic gas involved in the regulation of some essential biological processes. A novel, precise, accurate and rapid method based on high-performance liquid chromatography with diode array detection for the determination of sulfide ions in human urine sample is proposed. The method involves the derivatization of sulfide with pyrylium salts - (2,4,6-triphenylpyrylium hydrogensulfate(VI) (L1) and 4-[p-(N,N-dimethylamino)phenyl]-2,6-diphenylpyrylium chlorate(VII) (LN1). The separation occurs on InfinityLab Poroshell 120 EC C18 column using acetonitrile and phosphate buffer as a mobile phase. The detectors utilized a wavelength of 371 or 580 nm. The calibration curves were linear in the range of 2-150 µmol L-1 and 1-50 µmol L-1 for L1 and LN1 derivatives, respectively. The samples were found to be stable from sample collection to final analysis. The method was successfully applied to samples from apparently healthy volunteers.

A Green, Rapid and Efficient Dual-Sensors for Highly Selective and Sensitive Detection of Cation (Hg2+) and Anion (S2-) Ions Based on CMS/AgNPs Composites.

Detection of mercury (Hg2+) and sulfide (S2-), universal and well-known toxic ions, is crucial in monitoring several diseases. How to design and fabricate the high-performance sensor for simultaneously and accurately detecting the Hg2+ and S2- is critical. Herein, we proposed a novel and convenient strategy for optical detection of Hg2+ and S2- by employing a carboxymethyl cellulose sodium/silver nanoparticle (CMS/AgNPs) colloidal solution, in which AgNPs were used as monitor for Hg2+ and S2-, and the CMS was utilized as both the stabilizer and the hydrophilic substrate for AgNPs. Well-identifiable peaks for Hg2+ and S2- were obtained in water based on UV-VIS absorption spectra, the absorbance intensity and/or position of nano-silver vary with the addition of Hg2+ cation and S2- anion, accompanying with color change. Impressively, the optimal AgNPs anchored CMS exhibited a high sensitivity and selectivity toward Hg2+ and S2-, the change in absorbance was linear with the concentration of Hg2+ (0-50 µM) and S2- (15-70 µM), and the lowest limits of detection (LOD) were 1.8 × 10-8 M and 2.4 × 10-7 M, respectively. More importantly, owing to the superior properties in testing Hg2+ and S2-, the fabricated sensor was successfully applied for detection of target ions in lake and tap water samples. All these good results implied that the designed strategy and as-designed samples is promising in detecting cation (Hg2+) and anion (S2-) ions and open up new opportunities for selecting other kinds of ions.