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A simple and sensitive Pb${}^{2+}$ sensor is developed based on label-free 17E DNAzyme and unmodified Au nanoparticles. On this basis, Pb${}^{2+}$ concentration can be judged according to the color variation of Au nanoparticles. The detection limit is 100nM and linear range is 100nM–16$\mu$M. It can serve as a measurement tool for Pb${}^{2+}$ rapid detection, which provides reference for the development of sensors in environmental monitoring and food safety.

This paper describes some of our efforts in the area of nanostructured thin film architectures. The resulting interfacial hybrid assemblies are built from (1) organic/polymeric objects based on dendrimer systems, from (2) surface-functionalized Au nanoparticles, and (3) from a variety of semiconducting quantum dots. Dendrimers as polymeric building blocks with a strictly monodisperse particle size distribution in the nanometer range can be functionalized in the core, the scaffold, or at the periphery, thus offering interesting hybrid materials for a wide range of applications. The combination with Au clusters and their local surface plasmon resonances suggests new strategies for optoelectronic devices or unconventional bio-sensor platforms. The possibility of tuning the luminescent properties of semiconducting nanoparticles by size or compositional bandgap engineering complements the assembly kit with building blocks for supramolecular thin film nanocomposite materials.

We investigated the structure of citrates adsorbed on Au nanoparticles (AuNPs) synthesized by the Frens method by Fourier transformed infrared spectroscopy (FTIR). We found that physisorbed citrates are stable enough to stay on the surface of AuNPs during purification. The FT-IR spectra of citrates on AuNPs are quite uniquely different from bulk citrates, suggesting the formation of coordination bond between carboxylate group and gold. The shifts of carboxylate vibration modes on AuNPs are larger than that on flat Au substrates, as expected from the stronger dipole field on AuNPs compared with that on flat substrates.

Poly(divinylbenzene-co-acrylic acid) (poly(DVB-co-AA)) hollow microspheres with gold nanoparticles on the interior surfaces were prepared from the gold nanoparticles-coated poly(methacrylic acid) (PMAA@Au@poly(DVB-co-AA)) core-shell microspheres by removal of the PMAA core in water. Au nanoparticles-coated PMAA microspheres were afforded by the in-situ reduction of gold trichloride with PMAA microsphere as stabilizer via the interaction between carboxylic acid groups and Au nanoparticles. Gold nanoparticles-coated (PMAA@Au@poly(DVB-co-AA)) microspheres were formed during the distillation precipitation copolymerization of divinylbenzene and acrylic acid in acetonitrile with Au-coated PMAA microspheres as seeds. The thickness of the poly(DVB-co-AA) shell-layer was controlled by the amount of the solvent distilled off the polymerization system. The PMAA microspheres, Au nanoparticles-coated PMAA microspheres, core-shell microspheres, and hollow microspheres with Au nanoparticles on the interior surfaces were studied by transmission electron microscopy and scanning electron microscopy. The stabilization to L-cysteine and the preliminary catalytic property of the Au nanoparticles on the inner surface of hollow poly(DVB-co-AA) microspheres were investigated.

Preparation of gold nanoparticles by chemical reduction method using Preyssler heteropolyacid was investigated. The experimental conditions have been optimized using Taguchi robust design method with L9 orthogonal array. Particle size of the gold nanoparticles was considered as the property in the optimization. Amounts of Preyssler heteropolyacid, pH and irradiation time were selected as the main parameters. The result of Taguchi analysis has shown that in this process, the preyssler acid amount is the most influencing parameter on the size of gold nanoparticle. Also, the effects of different parameters are in order to: Preyssler acid amount > pH > irradiation time (negligible). This method showed that decreasing Preyssler amount and increasing pH of solution lead to formation of smaller nanoparticles. Finally, the prepared nanoparticles at optimum condition with a size of about 6.42 were characterized by using Dynamic Light Scattering (DLS) method, transmission electron microscopy (TEM), and UV-Vis spectroscopy.

Au nanoparticles anchored on core–shell $\alpha$-Fe₂O₃@SnO₂ nanospindles were successfully constructed through hydrothermal synthesis process and used for fabricating a novel nonenzymatic dopamine (DA) sensor. The structure and morphology of the Au/$\alpha$-Fe₂O₃@SnO₂ trilaminar nanohybrid film were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the sensor were investigated by cyclic voltammetry and amperometry. The experimental results suggest that the composites have excellent catalytic property toward DA with a wide linear range from 0.5$\mu$M to 0.47mM, a low detection limit of 0.17$\mu$M (S/$\mathrm{\text{N}}=3$) and high sensitivity of 397.1$\mu$AmM${}^{-1}$cm${}^{-2}$. In addition, the sensor exhibits long-term stability, good reproducibility and anti-interference.

A new type of multifunctional metal-organic frameworks (MOFs) was synthesized by encapsulating gold nanoparticles (AuNPs) into the Cu-hemin MOFs, and first applied to an electrochemical sensor to detect catechol (CT) with the aid of electrochemically reduced graphene oxide (ERGO) for signal amplification. First, ERGO was electrochemically deposited on a bare glass carbon electrode (GCE), followed by casting Cu-hemin MOFs on an ERGO-modified electrode, and then growing AuNPs in situ on Cu-hemin MOFs/ERGO/GCE by electrochemical deposition. Cyclic voltammetry (CV), scanning electron microscopy (SEM) and current–time ($I$–$t)$ were utilized to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The results demonstrated that Cu-hemin MOFs have not only been a matrix to avoid the aggregation of AuNPs but also an ideal loading platform for the adsorption of CT due to its large surface area and porosity. In addition, the ERGO also has the advantage of fast electron transfer, which can make synergy with AuNPs@Cu-hemin MOFs nanocomposites to amplify the electrical signal. The AuNPs/Cu-hemin MOFs/ERGO/GCE exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of CT. Under the optimum experimental conditions, the sensor shows a wide linear relationship over the range of $2.0\times 10^{-6}$M to $1.692\times 10^{-3}$M with a detection limit of $2.0\times 10^{-7}$M. Moreover, the sensor presented the good reproducibility and the excellent anti-interference performance. This work would broaden the application of MOFs material in constructing more novel electrochemical sensing platform.

Gold nanoparticles (AuNPs) modified with nitrogen-doped and nanoperforated graphene (DNPG) were successfully fabricated on a glassy carbon electrode (GCE). The composite showed excellent electrochemical response for hydrogen peroxide (H₂O${}_2)$ determination. Nitrogen-doped graphene has peroxidase-like activities. DNPG provided abundant surface area to support AuNPs, as well as ion transport shortcuts through the pores on DNPG sheets. DNPG and one-step electrode position of gold nanostructures can greatly improve conductivity and catalytic performance. The electroactive surface area of AuNPs/DNPG/GCE is almost 2.07 times higher than that of bare GCE. When AuNPs/DNPG/GCE were employed for non-enzymatic H₂O₂ sensing, the modified electrode presented an ultrahigh sensitivity of 5.3678 × 10${}^{-4}$ mA$\mu$mol L${}^{-1}$ cm${}^{-2}$ in the range of 0.5–10 mmol L${}^{-1}$, as well as excellent selectivity, reproducibility and stability. AuNPs/DNPG/GCE could serve as an electrochemical biosensor for the detection of disease biomarkers in clinical practice.