Singlet oxygen (1O2), generated via photosensitization, has been proved to oxidize chromogenic substrates with neither H2O2 oxidation nor enzyme (horseradish peroxidase, HRP) catalysis. Of the various methods for modulation of the 1O2 generation, DNA-controlled photosensitization received great attention. Therefore, integration of the formation/deformation DNA structures with DNA-controlled photosensitization will be extremely appealing in visual biosensor developments. Here, the stable melamine-thymine complex was explored in combination with DNA-controlled photosensitization for visual detection of melamine. A T-rich single stand DNA was utilized as the recognition unit. Upon the formation of the T-M-T complex, double stand DNA was formed, which was ready for the binding of SYBR Green I and activated the photosensitization. Subsequent oxidation of TMB allowed visual detection of melamine in dairy products, with spike-recoveries ranging from 94% to 106%.

Gold nanoparticles (AuNPs)-based colorimetric assays are of particular interest since molecular events can be easily read out with the color changes of AuNPs by the naked eye. However, the molecular recognitions occur almost exclusively in the liquid phase (i.e., the interaction between target analytes and AuNPs is always proceeded in the presence of the sample matrix). Since the aggregation of the unmodified AuNPs is prone to be influenced by the ionic strength of the solution, sample matrix will cause undesirable interference. Here, we proposed a new type of AuNP-based colorimetric assay, in which target analyte selenium was first converted to its hydride chemical vapor (H2Se) and then delivered into the solution of AuNPs to induce color change. Therefore, sample matrix (for example, high salinity) were eliminated, leading to excellent selectivity. With the aid of hydride generation, the proposed method offered a detection limit of 0.05 μM with UV–vis detection and 1 μM with the naked eye. Successful application of this method for selenium detection in biological and environmental samples was demonstrated.

A new digestion method using UV-assisted Fe0 Fenton reaction was developed for the determination of trace Cd in rice by hydride generation atomic fluorescence spectrometry. The proposed method integrated the advantages of simplicity, small dose of reagents, low cost and moderate reaction conditions, and was successfully utilized to analyze a Certified Reference Material (CRM) and real rice samples. A 1 mL mixture of the sample and reagents (0.0500 g rice powder, 0.2% (m/v) Fe0, 0.75% (v/v) HNO3 and 18% (v/v) H2O2) was irradiated by UV-light for 50 min and then a clear solution was obtained by separating excess Fe0 with a magnet prior to spectral analysis. The limit of detection (LOD) for Cd was found to be 0.02 mg kg−1 and the relative standard deviation was better than 5.0% at a concentration level of 0.40 mg kg−1. The recovery obtained by analyzing the CRM was 103% and spiked recoveries with 0.40 mg kg−1 Cd in rice samples were 93% and 101%. The t-test proved that there is no significant difference between the certified value and the determined value of the CRM, and between the proposed method and microwave-assisted digestion coupled with inductively coupled plasma mass spectrometry (MWD-ICP-MS) at 95% confidence level.

•Photochemical or ultrasonic vapor generation generates Hg0 from total mercury or inorganic Hg2 +.•Flow injection–vapor generation–atomic fluorescence spectrometry mode was adapted.•Ultrasensitive and matrix interference-free analysis was achieved.•Water and fish samples were successfully analyzed for trace mercury species.A simple, non-chromatographic and green method based on flow injection UV photochemical or ultrasonic vapor generation atomic fluorescence spectrometry (AFS) was developed for the determination and speciation analysis of mercury. Mercury cold vapor (Hg0) was generated by using only formic acid and UV or ultrasonic irradiation, and was subsequently detected by AFS. Both mercury (Hg2 +) and methyl mercury (MeHg) can be converted to Hg0 for the determination of total mercury with UV irradiation, while only Hg2 + can be reduced to Hg0 with ultrasonic irradiation, thus determining only Hg2 +. Then, the concentration of MeHg can be calculated by subtracting the Hg2 + concentration from the total mercury concentration. The optimal conditions for the best cold vapor generation efficiencies are discussed in detail, together with interference from transition metals. This new speciation analysis not only provides high sensitivity for the determination of mercury species but further eliminates the use of toxic reducing reagents and avoids potential destruction of analyte species that occur in chromatographic separation. Moreover, a simpler and less toxic Hg2 + standard series can be used for the calibration of both Hg2 + and MeHg. The limit of detection is 0.005 or 0.01 μg L− 1 for total mercury with the UV or inorganic mercury with the ultrasonic irradiation, respectively. This method was successfully applied to ultrasensitive mercury speciation analysis of water and biological samples.

•The proposed method could be easily performed without any pre-modification steps.•A theoretical study was also used to illustrate the mechanism of this system.•This colorimetric assay was simple, cost-effective, sensitive and selective.A facile yet sensitive and selective method was proposed for Hg2+ detection based on N-acetyl-L-cysteine(NAC)-induced colorimetric response of AuNPs. The proposed method can be easily performed by introducing the premixing of NAC and Hg2+ into as-prepared citrate-capped AuNPs solution. A combination of experimental and theoretical studies was applied to illustrate the mechanism of this AuNPs colorimetric system. The strong interaction of NAC and AuNPs through Au–S bond could lead to the aggregation of AuNPs, but the formation of NAC-Hg-NAC complex decreased the affinity between NAC and AuNPs and resulted in an anti-aggregation effect. Therefore, the color of the AuNPs solution would progress from purple to red with the increase of Hg2+ concentration. The proposed method had a high sensitivity with a limit of detection of 9.9 nM. Coexistent metal ions, including Cd2+, Mn2+, Al3+, Ag+, K+, Mg2+, Ca2+, Cr3+, Cu2+, Fe3+, Pb2+, Ni2+ and Zn2+, did not interfere with the detection of Hg2+. This method can be used to monitor Hg2+ in tap water.

•Acetone adsorption prefers to take place on the top site with the symmetry plane of acetone perpendicular to the bridge oxygen rows.•The 3d transition metal doping is getting harder with the increase of atomic number of the doping atom.•The Mn, Co and Ni doping leads to acetone activation, but the Fe doping may reduce the activity.The adsorption of acetone on the pure and V-, Cr-, Mn-, Fe-, Co-, Ni-doped (TiO2)38 clusters was studied by the density functional theory (DFT) with the generalized gradient approximation (GGA) developed by the Perdew and Wang (PW91) exchange-correlation functional. The structural studies indicate that acetone adsorption prefers to take place on the top site with the symmetry plane of acetone perpendicular to the bridge oxygen rows. The properties of transition metal doped clusters were also been discussed. The calculated substitution energies show that the 3d transition metal doping is getting harder with the increase of atomic number of the doping atom. Furthermore, the adsorption of acetone on the doped clusters was investigated. The adsorption energies of Mn-, Co- and Ni-doped clusters are obviously larger than that of pure TiO2 cluster. The Mn, Co or Ni doping leads to acetone activation mainly on the CO group, but the Fe doping may reduce the activity.

Using density functional theory (DFT), adsorption of O2 and co-adsorption of O2 and CCl4 on (ZnS)n clusters (n = 6, 7, 11, 12, 13, 15, 16, 17, 25, 26) and the mechanism of oxidative decomposition of CCl4 on a ZnS nanocluster were investigated. The decomposition of CCl4 without the ZnS cluster was also studied for comparison. The ZnS cluster achieved a significant catalytic effect during the oxidative decomposition of CCl4. It is found that CCl4 in gas phase undergoes a homolytic dissociation process with the activation by ZnS, reacting with O2 to produce a CCl3˙ radical and a ClOO˙ radical first. CO2 and Cl2 are identified as the final neutral reaction products, while COCl2, CO and Cl2O are produced as intermediates. The released energy of the total reaction, 149.83 kcal mol−1, is sufficient to afford the transition energy of the cataluminescence, based on which a novel and sensitive gas sensor for the determination of CCl4 could be constructed.

A new analytical method was developed to determine trace arsenic in soil by coupling sequential injection multichannel ultrasonic extraction and online pre-reduction with slurry hydride generation atomic fluorescence spectrometry. Significantly enhanced sampling throughput, reduced sample and reagent consumption, and minimized potential contamination and analyte loss were achieved. Slurry samples spiked with different concentrations of As(III) and hydrochloric acid were pumped into the ultrasonic extraction chamber for 20-minute irradiation to efficiently extract As, which were subsequently merged with a mixture of 1% (m/v) thiourea and 0.5% (m/v) ascorbic acid to pre-reduce As(V) species to As(III), followed by the generation of AsH3via using KBH4. Upon optimization of experimental parameters, limits of detection (LODs) ranging from 30 to 70 ng g−1 were obtained, and the precisions (RSDs) of this method were better than 2.0%. The proposed method was used for the determination of trace arsenic in several Certified Reference soil samples, with the obtained results in excellent agreement with certified values based on a simple and fast standard addition method.

A highly sensitive and selective detection method for mercury(II) in aqueous samples was developed based on the use of an oligonucleotide-based label-free fluorescent probe. The novel design was composed of two oligonucleotides with partially complementary sequences and the label-free dye ethidium bromide (EB). The fluorescence signal was very low when EB was free in water solution. However, the fluorescence signal increased by nearly 15 times when the DNA duplex was present. This dsDNA–EB system was used as a fluorescent sensor for Hg2+. The presence of Hg2+ led to the release of EB from the grooves of dsDNA and the fluorescence intensity was quenched. In this investigation, the optimal concentrations of dsDNA and EB were 0.285 μM and 0.9 μM, respectively. The calibration curve was linear in the range of 30 to 120 nM for Hg2+ (R2 = 0.992), with a detection limit of 9.5 nM. The method was simple and convenient, and this sensor also provided potential applications for developing aptasensors.

A novel and highly sensitive gas sensor for triethylamine (TEA) was proposed based on its cataluminescence (CTL) from the catalytic oxidation on the surface of nano-sized LaF3–CeO2. The LaF3–CeO2 nanoparticles were successfully prepared by using a calcination method. The luminescence characteristics and the optimal conditions were investigated in detail. Under the optimal conditions, the present gas sensor exhibited a linear range of 0.9–54 ppm, with a correlation coefficient (R) of 0.9987 and a limit of detection (S/N = 3) of 0.2 ppm. The relative standard deviation (R.S.D.) for 36.5 ppm triethylamine was 4.3% (n = 6). There was no significant change in the catalytic activity of the sensor after 6 days, with a R.S.D. less than 5%. The proposed triethylamine sensor showed the advantages of good sensitivity and high selectivity.

In the present work, hydride generation, as one of widespread application techniques in elemental analysis with the advantage of the excellent matrix separation, was attempted into the chemiluminescence. The experiment exhibited that the strong chemiluminescence emission can be obtained during the reaction between hydrogen telluride and luminol in basic medium, and a novel sensitive hydride generation-chemiluminescence (HG-CL) methodology for the determination of tellurium was proposed. Under the optimized conditions, the linear range of CL intensity versus concentration of tellurium (IV) was 10–200 μg L− 1, with a coefficient (R) of 0.997 and a limit of detection (S/N = 3) of 2 μg L− 1. The results showed that the method provided superior performance with respect to tolerance to various coexisting ions such as Mg2+, Ca2+, Fe3+, Zn2+, Pb2+, As3+, Ge2+, and Hg2+. The proposed method has the advantages of simplicity, selectivity, and sensitivity, with a potential of detecting tellurium in environmental and biological samples.

A novel and sensitive gas sensor was proposed for the determination of carbon tetrachloride based on its cataluminescence (CTL) by oxidation in the air on the surface of nanosized ZnS. The luminescence characteristics and the optimal conditions were investigated in detail. Under the optimized conditions, the linear range of the CTL intensity versus the concentration of carbon tetrachloride was 0.4–114 μg mL−1, with a correlation coefficient (R) of 0.9986 and a limit of detection (S/N = 3) of 0.2 μg mL−1. The relative standard deviation (R.S.D.) for 5.9 μg mL−1 carbon tetrachloride was 2.9% (n = 5). There was no or weak response to common foreign substances including methanol, ethanol, benzene, acetone, formaldehyde, acetaldehyde, dichloromethane, xylene, ammonia and trichloromethane. There was no significant change of the catalytic activity of the sensor for 40 h over 4 days, with a R.S.D. of less than 5% by collecting the CTL intensity once an hour. The proposed method was simple and sensitive, with a potential of detecting carbon tetrachloride in environment and industry grounds. The possible mechanism was also discussed briefly.

A highly sensitive and selective detection method for mercury(II) in aqueous samples was developed based on the use of an oligonucleotide-based label-free fluorescent probe. The novel design was composed of two oligonucleotides with partially complementary sequences and the label-free dye ethidium bromide (EB). The fluorescence signal was very low when EB was free in water solution. However, the fluorescence signal increased by nearly 15 times when the DNA duplex was present. This dsDNA–EB system was used as a fluorescent sensor for Hg2+. The presence of Hg2+ led to the release of EB from the grooves of dsDNA and the fluorescence intensity was quenched. In this investigation, the optimal concentrations of dsDNA and EB were 0.285 μM and 0.9 μM, respectively. The calibration curve was linear in the range of 30 to 120 nM for Hg2+ (R2 = 0.992), with a detection limit of 9.5 nM. The method was simple and convenient, and this sensor also provided potential applications for developing aptasensors.

Using density functional theory (DFT), adsorption of O2 and co-adsorption of O2 and CCl4 on (ZnS)n clusters (n = 6, 7, 11, 12, 13, 15, 16, 17, 25, 26) and the mechanism of oxidative decomposition of CCl4 on a ZnS nanocluster were investigated. The decomposition of CCl4 without the ZnS cluster was also studied for comparison. The ZnS cluster achieved a significant catalytic effect during the oxidative decomposition of CCl4. It is found that CCl4 in gas phase undergoes a homolytic dissociation process with the activation by ZnS, reacting with O2 to produce a CCl3˙ radical and a ClOO˙ radical first. CO2 and Cl2 are identified as the final neutral reaction products, while COCl2, CO and Cl2O are produced as intermediates. The released energy of the total reaction, 149.83 kcal mol−1, is sufficient to afford the transition energy of the cataluminescence, based on which a novel and sensitive gas sensor for the determination of CCl4 could be constructed.

A new analytical method was developed to determine trace arsenic in soil by coupling sequential injection multichannel ultrasonic extraction and online pre-reduction with slurry hydride generation atomic fluorescence spectrometry. Significantly enhanced sampling throughput, reduced sample and reagent consumption, and minimized potential contamination and analyte loss were achieved. Slurry samples spiked with different concentrations of As(III) and hydrochloric acid were pumped into the ultrasonic extraction chamber for 20-minute irradiation to efficiently extract As, which were subsequently merged with a mixture of 1% (m/v) thiourea and 0.5% (m/v) ascorbic acid to pre-reduce As(V) species to As(III), followed by the generation of AsH3via using KBH4. Upon optimization of experimental parameters, limits of detection (LODs) ranging from 30 to 70 ng g−1 were obtained, and the precisions (RSDs) of this method were better than 2.0%. The proposed method was used for the determination of trace arsenic in several Certified Reference soil samples, with the obtained results in excellent agreement with certified values based on a simple and fast standard addition method.