•This is the first report for the synthesis of GNCs through L-tryptophan by one-step method.•This is the first report for the synthesis of dual-emissions GNCs through amino acids.•This is the first report on using ratiometric fluorescent probe based on GNCs to detect Fe3+ in the serum samples.A novel dual-emission fluorescent gold nanoclusters (GNCs) was first synthesized through a one-step method. In the method, the L-tryptophan acted as both the reducing and protecting agents at the same time. The dual-emission bands of the GNCs were found around 360 nm and 450 nm, respectively. The fabricated GNCs were selectively quenched by Fe3+ ion in the presence of EDTA. The GNCs were successfully used as a ratiometric sensor to detect Fe3+ with a linear range from 1 to 500 μM (R2 = 0.9970) and a detection limit as low as 0.16 μM. The relative standard deviation (RSD) at 1 μM for Fe3+ of six repetitive measurements was 0.12%. The practicability of the GNCs was validated by the analysis of serum samples and more than 94% recoveries were obtained. The results indicated that the GNCs possess great potential value for application in biological analysis.

A simple, rapid, and inexpensive method for the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide conjugated gold nanoclusters (RGD-GNCs) was reported. The nanoclusters were synthesized with chloraurate as precursor and cyclic RGD peptides as both reducing and protecting agent directly under alkali condition, and the whole synthetic process only took 15 min at room temperature. The properties of the nanoclusters were characterized by means of ultraviolet–visible spectra, Fourier transform infrared spectroscopy (FTIR), fluorescence, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared gold nanoclusters were successfully used as a contrast agent in fluorescence imaging of the melanoma A375 cells, which overexpress the integrin αvβ3. The results demonstrated that our nanoclusters possess good biocompatibility, stability, and low toxicity. Moreover, the method is expected to be applicable to the synthesis of nanoclusters conjugated with other biomolecules.

•We developed a new signal model for electronic nose with metal oxide semiconductor.•The model relates the signal intensity and the absorbed odorant on sensors.•The mathematical expression of the model is not a bilinear or trilinear form.Electronic noses have found wide applications as a promising tool in many fields. However, a model for their signals has not been clearly elucidated thus far. Here, we have developed a signal model for electronic noses based on the relationship between the signal intensity and the amount of odorant molecules absorbed onto the surface of a sensor. We applied an alternative least square algorithm to solve the model. We successfully applied this model to the analysis of benzene and six perfumes using data from a commercial system.

A novel electrochemical sensor for the simultaneous detection of guanine (G) and adenine (A) was developed on a Pd nanowire arrays-modified carbon glassy electrode (Pd NWAs). The Pd NWAs were obtained via the direct electrode position of Pd on a glassy carbon electrode within the pores of an anodized aluminum oxide membrane. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDS) techniques were used to examine the Pd NWAs structures. The Pd nanowire arrays have high electrochemically active surfaces, and this modified electrode exhibits excellent and persistent electro-oxidation behavior toward G and A. The Pd NWAs modified electrodes significantly increases oxidation peak currents but reduces the peaks potential of G and A. For the Pd NWAs-modified electrode, the peak potentials of G and A are negatively shifted to 0.69 and 0.97 V, respectively. Differential pulse voltammetry (DPV) was proposed for the simultaneous determination of G and A. Under the selected conditions, the oxidation peak currents were proportional to guanine and adenine, ranging from 2 μM to 200 μM and 4 μM to 200 μM with detection limits at 0.7 μM and 1 μM, respectively. Simultaneously, the proposed method was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfactory results.

•A “turn on” fluorescent chemosensor was developed to detect Ag+ ions.•The binding of chemosensor with Ag+ ions forms fluorescent nanoaggregates.•The chemosensor bonds Ag+ ions with a stoichiometric ratio of 1:2.•A 14-fold fluorescence enhancement with a large stokes shift (135 nm) was observed.•A low detection limit of 8.74 × 10−7 M was obtained.A new fast-responsive “turn on” fluorescent sensor for Ag+ was successfully developed by taking advantage of the aggregation-induced emission (AIE) property of tetraphenylethylene motif with a detection limit of 8.74 × 10−7 M. The sensor exhibits highly selective and sensitive recognition toward Ag+ ions over the other 12 metal ions due to the high electrophilic and thiophilic character of Ag+ ions. The 1H NMR titration and dynamic light scattering (DLS) spectra conclude that the binding of the sensor with Ag+ ions forms fluorescent nanoaggregates in aqueous media due to its AIE enhancement. A stoichiometric ratio (1:2) of the sensor and Ag+ was determined by a Job’s plot.

Stepwise key spectrum selection (SKSS) was introduced to resolve batch overlapping peaks from gas chromatography–mass spectrometry (GC–MS) analysis of ten batch tobacco flavoring samples in different storage times. Resolution was implemented on a software platform that embedded the SKSS method. The data from GC–MS analysis of the samples were saved and prepared in ASCII files and then were inputted into the software platform for visual inspections. The data segment with overlapping peaks was precut for subsequent analysis. Spectral background in the data was removed using a linear fitting of the baseline. Four components in the overlapping peaks were automatically detected by the SKSS method. The resolution of the concentration profiles and spectra of the four components was conducted by setting only one parameter, the negative area ratio, as 0.01. The fixed size moving window evolving factor analysis and evolving factor analysis were applied to validate the resolved concentration profiles. The resolved mass spectra were validated by the searched standard through library search at the pure component regions revealed by the resolved concentration profiles. The results showed that the SKSS method could be a simple but powerful tool in resolving batch chromatographic overlapping peaks.

A spectral similarity measure was developed that can differentiate subtle differences between two spectra. The spectra are digitalized into a vector. The difference between the two spectra is defined by a difference vector, which is one spectrum minus the other. The spectral similarity measure is transformed into a hypothesis test of the similarities and differences between the two spectra. The scalar mean of the difference vector is used as the statistical variable for the hypothesis test. A threshold for the hypothesis that the spectra are different was proposed. The Bayesian prior odds ratio was estimated from multiple spectra of the same sample. The posterior odds ratio was used to quantity the spectral similarity measure of the two spectra. Diffuse reflectance near-infrared spectra of tobacco samples of two formulations were used to demonstrate this method. The results show that this new method can detect subtle differences between the spectra.

A novel electrochemical sensor for the simultaneous detection of guanine (G) and adenine (A) was developed on a Pd nanowire arrays-modified carbon glassy electrode (Pd NWAs). The Pd NWAs were obtained via the direct electrode position of Pd on a glassy carbon electrode within the pores of an anodized aluminum oxide membrane. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDS) techniques were used to examine the Pd NWAs structures. The Pd nanowire arrays have high electrochemically active surfaces, and this modified electrode exhibits excellent and persistent electro-oxidation behavior toward G and A. The Pd NWAs modified electrodes significantly increases oxidation peak currents but reduces the peaks potential of G and A. For the Pd NWAs-modified electrode, the peak potentials of G and A are negatively shifted to 0.69 and 0.97 V, respectively. Differential pulse voltammetry (DPV) was proposed for the simultaneous determination of G and A. Under the selected conditions, the oxidation peak currents were proportional to guanine and adenine, ranging from 2 μM to 200 μM and 4 μM to 200 μM with detection limits at 0.7 μM and 1 μM, respectively. Simultaneously, the proposed method was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfactory results.