We have demonstrated a novel way to form thickness-controllable polyelectrolyte-film/nanoparticle patterns by using a plasma etching technique to form, first, a patterned self-assembled monolayer surface, followed by layer-by-layer assembly of polyelectrolyte-films/nanoparticles. Octadecyltrimethoxysilane (ODS) and (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayers (SAMs) were used for polyelectrolyte-film and nanoparticle patterning, respectively. The resolution of the proposed patterning method can easily reach approximately 2.5 μm. The height of the groove structure was tunable from approximately 2.5 to 150 nm. The suspended lipid membrane across the grooves was fabricated by incubating the patterned polyelectrolyte groove arrays in solutions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs). The method demonstrated here reveals a new path to create patterned 2D or 3D structures.

This study developed a method on detecting methyl viologen (paraquat) using a CdTe-paper-based visual sensor. The CdTe Qdots were immobilized on the paper using glycerin. The volume percentages of CdTe in glycerin were optimized to be 50%. The sensing principle is that the methyl viologen quenches the fluorescence intensity of CdTe Qdots in a concentration dependent manner. The sensor is linearly response to the logarithm concentration of the methyl viologen in the range from 0.39 µmol/L to 3.89 mmol/L with a detection limit of 0.16 µmol/L and the correlation coefficient R² of 0.99. Three parallel experiments at the methyl viologen concentration of 38.89 µmol/L give a relative error of 2.45%, which indicates a good reproducibility. The sensor is not disturbed by other pestisides including omethoate, anilofos, machete and glyphosate isopropylamine salt. The advantages of this sensor are disposable, stable, convenient, and easy to operate.

A sensitive electrochemical method for square-wave voltammetric detection of organophosphate (OP) compounds was developed based on zirconia (ZrO₂) nanoparticles modified electrode. The electrode was fabricated using electrochemical deposition and characterized by scanning electron microscopy (SEM), which confirmed the successful formation of nanoparticles. Due to the strong affinity of ZrO₂ with the phosphoric group, nitroaromatic OPs can strongly bind to the surface of ZrO₂ nanoparticles (ZrO₂NPs). Under optimized operational conditions, SWV was employed for Omethoate (a model of OP compounds) detection with 5 min absorption, which showed a wide detection range from 98.5 pmol·L⁻¹ to 985 nmol·L⁻¹, with a detection limit as low as 52.5 pmol·L⁻¹. This electrochemical sensor has good selectivity, stability and reproducibility, and great potential in the detection of OP compounds in agriculture area.

Palladium nanotubes were fabricated by using lipid tubules as templates for the first time in a controlled manner. The positively charged lipid 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) was doped into lipid tubules to adsorb PdCl₄²⁻ on the tubule surfaces for further reduction. The lipid tubule formation was optimized by studying the growing dynamics and ethanol/water ratio. The DOTAP-doped tubules showed pH stability from 0 to 14, which makes them ideal templates for metal plating. The Pd nanotubes are open-ended with a tunable wall thickness. They exhibited good electrocatalytic performance in ethanol. Their electrochemically active surface areas were 6.5, 10.6, and 83.2 m² g⁻¹ for Pd nanotubes with 77, 101, and 150 nm wall thickness, respectively. These Pd nanotubes have great potential in fuel cells. The method demonstrated also opens up a way to synthesize hollow metal nanotubes.

The ability to engineer the surface properties of magnetic nanoparticles is important for their various applications, as numerous physical and chemical properties of nanoscale materials are seriously affected by the chemical constitution of their surfaces. For some specific applications, nanoparticles need to be transferred from a polar to a nonpolar environment (or vice versa) after synthesis. In this work we have developed a universal method for the phase transfer of magnetic nanoparticles that preserves their shape and size. Octadecyltrimethoxysilane was used to cap the surfaces of the aqueous magnetic nanoparticles, thereby allowing their transfer into nonpolar solution. The resulting hydrophobic magnetic nanoparticles were transferred back into aqueous solution by subsequently covering them with an egg-PC lipid monolayer. The superparamagnetic properties of the particles were retained after the phase transfer. The maximum transfer yields are dependent on their particle size with a maximum value of 93.16±4.75 % for magnetic nanoparticles with a diameter of 100 nm. The lipid-modified magnetic particles were stable over 1 week, and thus they have potential applications in the field of biomedicine. This work also provides a facile strategy for the controllable engineering of the surface properties of nanoparticles.

A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer-by-layer technique on a silicon oxide surface modified with a 3-aminopropyltriethoxysilane (APTES) monolayer. The surface pK_a value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer-by-layer assembly. Micropatterned polyelectrolyte films were obtained by deep-UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm² s⁻¹ in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field.

A novel, simple, versatile, rapid, and inexpensive method, “space limited oxygen plasma oxidation” is developed to fabricate chemical gradient on both alkylsilane and alkanethiol self-assembled monolayers (SAMs) surface. XPS data confirm that the methyl groups of alkane SAMs are converted into oxidized carbon functional groups. The influences of RF power, O₂ flow rate, and the “wedge” shape on gradient formation are investigated in details. Gradient surfaces with various scales and depths are formed by simply changing the ‘wedge’ shape or plasma generation parameters. The application of formed chemical gradient on droplet motion has been demonstrated as well.