Gold nanoclusters (Au NCs) have attracted great interest for unique size-dependent properties, and more properties and applications are still encouraged to be explored and understood. Here we observed an unexpected emission from luminol upon injection of Au NCs, which did not require excitation, strong alkaline-pH regulation, or addition of oxidants, being different from the traditional fluorescence and chemiluminescence. On the basis of both experimental and computational data, the emission was shown to be generated from radical-mediated spin-transfer on Au NCs. Species of O2•– were identified as primary radicals that triggered the spin-transfer from the triplet state of O2 to the aminobenzene ring of luminol by the aids of Au NCs, leading to an efficient phosphorescence. Subsequently, a sensor array composed of five protein-protected Au NCs was fabricated for protein discrimination. This work not only provides new insights of Au NCs into luminol emission but also shows potentials in protein discrimination.

By simple microwave irradiation, a high-throughput, single-step, rapid but controllable synthesis of stable colloidal CsPbX3 perovskite NCs with tunable properties and morphologies (nanocubes, nanorods, nanowires, quadrate nanoplates and hexagonal nanoplates) was achieved. It was employed in a heterogeneous solid–liquid reaction system within minutes without any tedious pre-preparation.

Point mutation, with a permanent change in nucleic acid sequences, can affect the expression of genetic information forming the basis for numerous human genetic diseases, which makes its detection crucially important. Here, we reported a simple and sensitive method for point mutation detection, which employs a core–shell gold nanocube (Au NC) based on plasmon-enhanced fluorescence (PEF). For the generation of PEF, a Au NC was chosen as a core and silica as a spacer layer to adjust the distance between the Au NC and the dye of 5-carboxyfluorescein. Cu2+ quenched fluorescence by the interaction with the dye, while a “turn-on” signal was observed with the presence of pyrophosphate (PPi) owing to the strong affinity between Cu2+ and PPi, which subsequently achieved sensitive and selective detection of PPi. The experiment and theoretical simulations indicated that the enhanced signal was generated from square scattering cross sections and multiple corners, which could also be applied to cell imaging. Moreover, the rolling circle amplification coupled with ligase chain reaction (L-RCA) assay was also performed, which generated a circular DNA to initiate the RCA reaction accompanied by the generation of PPi that can be detected by the PEF sensor. Therefore, point mutation (C to T) can be detected based on fluorescence changes with a detection limit of 1.3 pM. This is a specific, simple, and economical method for point mutation detection, which overcomes the shortcomings of traditional detections of RCA products and point mutation.

•CTL emission on the paper substrates was firstly obtained with plasma assistance.•The system operated temperature was at room temperature.•The CTL emission was affected by metal ions, nanomaterials, and substrates.•A paper-based plasma-assisted CTL sensor was fabricated for ethylene sensing.•The first example of CTL imaging on the paper substrates was provided.The development of paper-based sensing devices has grown exponentially due to the unique properties of paper as a low-cost functional material. For a long period, paper-based cataluminescence (CTL) sensing devices were considered impractical because the operating temperature of CTL reactions is normally higher than 200 °C. Herein, we report, at the first time, a paper-based sensing system based on the CTL emission with the assistance of low-temperature plasma generated by air, which can be operated at room temperature. As demonstrated, enhanced catalytic ability and reactivity of the analytes were achieved, and CTL emission was obtained at room temperature, catalyzed by 0.320 wt% Mn-doped SiO2 nanomaterials on paper substrates. The CTL emission was affected by the type and relative amount of metal ions or nanomaterials, and different CTL intensities were obtained with different substrates. By optimization of the system, a paper-based CTL sensor was successfully fabricated for ethylene sensing. The sensor exhibited a wide linear response range and a limit of detection (LOD) at the ppm level. Good selectivity as well as the stability of the system was also demonstrated, and the first example of CTL imaging on paper substrates was provided. This approach furnishes a dramatically simplified CTL system, and the paper-based room temperature CTL sensor is expected to expand the applications of CTL.Download high-res image (138KB)Download full-size image

Carbon nanodots (C-dots) are recently well examined due to the emissions with color-tuning and nonblinking properties, while more studies are still needed for the appropriate understanding and application of distinct emissions. In this work, we found the emission of chemiluminescence (CL) by introducing low-temperature plasma (LTP) into C-dots solutions without any reagent added, whose intensity was affected by the presence of different metal ions. Based on both experimental data and theoretical calculations, we found with the ozonation by ozone from LTP, excited oxidized-C-dots would be generated with the addition of ozone onto the conjugated double bonds of C-dots, and these excited species could directly initiate strong CL combining with the deactivation of excited species to the ground state. Significantly, the cross-reactive CL signals were obtained from different kinds of C-dots with the presence of different metal ions. Therefore, a new sensor array (electronic tongue) composed of five different C-dots was designed for fast discrimination of metal ions, which achieved the accurate discrimination of 13 kinds of metal ions in pure water and real samples. It exhibited good reproducibility and sensitivity, which can be used for the quantitative analysis of metal ions such as showing a linear range from 4 × 10–7 to 6 × 10–5 mol·L–1 (R2 > 0.99) for Fe3+ with a detection limit of 2.5 × 10–7 mol·L–1. This work not only provides a novel finding of CL from C-dots revealing explicit relationship between structures and CL properties, but also realizes the fast discrimination of metal ions, showing potentials in environmental monitoring and quality identifications.

•In-situ nanoelectrospray was designed for direct sampling and ionization for MS.•It was fabricated by only inserting capillary into high-voltage applied liquid phase.•Analytes in liquid reaction phase were directly extracted and ionized for MS.•It achieved high-throughput enzyme evaluation and fast optimizations.•It has been used for real-time monitoring of enzyme catalyzed reactions.The in-situ and high-throughput evaluation of enzymes and real-time monitoring of enzyme catalyzed reactions in liquid phase is quite significant in the catalysis industry. In-situ nanoelectrospray, the direct sampling and ionization method for mass spectrometry, has been applied for high-throughput evaluation of enzymes, as well as the on-line monitoring of reactions. Simply inserting a capillary into a liquid system with high-voltage applied, analytes in liquid reaction system can be directly ionized at the capillary tip with small volume consumption. With no sample pre-treatment or injection procedure, different analytes such as saccharides, amino acids, alkaloids, peptides and proteins can be rapidly and directly extracted from liquid phase and ionized at the capillary tip. Taking irreversible transesterification reaction of vinyl acetate and ethanol as an example, this technique has been used for the high-throughput evaluation of enzymes, fast optimizations, as well as real-time monitoring of reaction catalyzed by different enzymes. In addition, it is even softer than traditional electrospray ionization. The present method can also be used for the monitoring of other homogenous and heterogeneous reactions in liquid phases, which will show potentials in the catalysis industry.

Based on cataluminescence from plasma-assisted catalytic oxidation, a low temperature CO sensor was fabricated. With Ag doped alkaline-earth catalyst as sensing element, air as discharge gas, carrier gas and oxidant supplier, significant cataluminescence was achieved at low temperature, demonstrating a potential low-consumption and portable sensor of CO.

In this article, a Venturi electrosonic spray ionization (V-ESSI) cataluminescence (CTL) sensor array was reported for discriminating saccharides in solution. Integrating electrosonic spray ionization (ESSI), a liquid system of Venturi self-pumping injection for the CTL reaction, was fabricated for enhancing CTL reactivity of aqueous samples. Comparing with simple Venturi injection by air and Venturi easy ambient sonic-spray ionization without electric assistance (V-EASI), the remarkable enhancement of CTL signals resulted from V-ESSI. This system showed higher cross-reactive CTL responses catalyzed by alkaline earth metal-nanomaterials than other catalysts, giving different signals for a given saccharide on different catalysts and different responses for different saccharides on the same catalyst. Then, a 4 × 2 CTL sensor array was used for obtaining “fingerprints” of distinct CTL response patterns. Analyzed by linear discriminant analysis (LDA), this V-ESSI CTL sensor array not only achieved the well discrimination of different saccharides (99.9% of total variation) but also discriminated four groups of urine sugar-level for urine samples from diabetic patients (98.1% of discrimination accuracy). It had good reproducibility and gave a linear range of 22.5–67558 μg/mL (R > 0.99) for xylose with a detection limit of 7.4 μg/mL on MgO. As a new artificial tongue, this system provided a simple, rapid, low cost, low energy consumption, and environmentally friendly pathway for aqueous sample discrimination. It has dramatically expanded applications of the CTL-based senor array and will be applicable to clinical diagnoses, environment monitoring, industrial controls, food industry, and various marine monitoring.

We describe direct analysis of self-assembled monolayers (SAMs) on copper surfaces by low temperature plasma (LTP) mass spectroscopy (MS). Two kinds of SAMs formed from n-dodecylmercaptan (NDM) and l-phenyl-5-mercaptotetrazole (PMTA) were prepared on copper by spontaneous chemisorption. With the LTP probe, desorption and ionization of the SAMs was easily achieved, and the ions produced were introduced into MS for analysis. Characteristic fragment ions from NDM SAMs, mainly [M + M – H]+ (M is the NDM molecule) and from PMTA SAMs, mainly [M + H – S]+ (M is the PMTA molecule), were both absent in the MS spectra of neat NDM and PMTA samples. This provided evidence of the formation of SAMs on copper. As a supplementary method, LTP-MS is helpful in obtaining information on the barrier properties of SAMs on copper, such as inhibitor efficiency (IE) and the surface adsorption concentration of corrosive electrolyte (Γ*) surrounding copper. Aiming for an evaluation of the reliability of LTP-MS, a comparative study of our method and the traditional method of cyclic voltammetry (CV) showed a correlation coefficient higher than 0.97. In addition, a rough, simple procedure for imaging of the distribution of the molecules adsorbed on copper surface was presented. The study supplied a rapid and simple method for direct investigation of SAMs on copper.

We report in this manuscript, the use of direct ammonium persulfate-enhanced chemiluminescence (CL) imaging, to monitor changes to measure serum salbutamol concentration in subjects of different haptoglobin (Hp) phenotypes at different dosing time. It was noted that CL generated from Hp was decreased due to salbutamol's reducibility, which was used for monitoring salbutamol concentration in serum. The serum from the subjects treated by oral administration of salbutamol, was collected at different dosing time and was separated by polyacrylamide gel electrophoresis (PAGE) prior to the CL detection. According to CL images, samples were separated into three groups based on the Hp phenotypes. The curves of CL signal intensity versus time were obtained for each group, and we demonstrated that there were more significant variables on binding ability between groups. The maximum salbutamol concentration in the serum appeared after 4 h, which was in agreement with the literature. In addition, the binding constants of salbutamol to Hp were determined by a fluorescence-based method, whose results were in agreement with the phenomenon of the greater salbutamol metabolism rate for Group Hp 1-1 than Group Hp 2-2. The presented method can monitor changes of salbutamol concentration in serum directly, making the procedures much simple, convenient, rapid and has the property of lower cost. It provided us with excellent reference information for the individual dosage regimen of different Hp groups, which hopefully could become a potential method for further pharmaceutical research.

Point mutation, with a permanent change in nucleic acid sequences, can affect the expression of genetic information forming the basis for numerous human genetic diseases, which makes its detection crucially important. Here, we reported a simple and sensitive method for point mutation detection, which employs a core–shell gold nanocube (Au NC) based on plasmon-enhanced fluorescence (PEF). For the generation of PEF, a Au NC was chosen as a core and silica as a spacer layer to adjust the distance between the Au NC and the dye of 5-carboxyfluorescein. Cu2+ quenched fluorescence by the interaction with the dye, while a “turn-on” signal was observed with the presence of pyrophosphate (PPi) owing to the strong affinity between Cu2+ and PPi, which subsequently achieved sensitive and selective detection of PPi. The experiment and theoretical simulations indicated that the enhanced signal was generated from square scattering cross sections and multiple corners, which could also be applied to cell imaging. Moreover, the rolling circle amplification coupled with ligase chain reaction (L-RCA) assay was also performed, which generated a circular DNA to initiate the RCA reaction accompanied by the generation of PPi that can be detected by the PEF sensor. Therefore, point mutation (C to T) can be detected based on fluorescence changes with a detection limit of 1.3 pM. This is a specific, simple, and economical method for point mutation detection, which overcomes the shortcomings of traditional detections of RCA products and point mutation.