A gold coated polystyrene ring microarray formed by two-step patterning: construction of an advanced microelectrode for voltammetric sensing

Designable Poly(methacrylic Acid)/Silver Cluster Ring Arrays as Reflectance Spectroscopy-Based Biosensors for Label-Free Plague Diagnosis

A hole array was fabricated via photolithography to wet the bottoms of holes using oxygen plasma. Amide-terminated silane, a water immiscible compound before hydrolysis, was evaporated for deposition on the plasma-treated hole template surface. The silane compound was hydrolyzed along the edges of circular sides of the hole bottom to form a ring of an initiator after halogenation. Poly(methacrylic acid) (PMAA) was grafted from the ring of the initiator to attract Ag clusters (AgCs) as AgC-PMAA hybrid ring (SPHR) arrays via alternate phase transition cycles. The SPHR arrays were modified with a Yersinia pestis antibody (abY) to detect the antigen of Yersinia pestis (agY) for plague diagnosis. The binding of the agY onto the abY-anchored SPHR array resulted in a geometrical change from a ring to a two-humped structure. The reflectance spectra could be used to analyze the AgC attachment and the agY binding onto the abY-anchored SPHR array. The linear range between the wavelength shift and agY concentration from 30 to 270 pg mL^-1 was established to obtain the detection limit of ~12.3 pg mL^-1. Our proposed method provides a novel pathway to efficiently fabricate a ring array with a scale of less than 100 nm, which demonstrates excellent performance in preclinical trials.

Playing with sizes and shapes of colloidal particles via dry etching methods

Monolayers of self-assembled quasi-spherical colloidal particles are essential building blocks in the field of materials science and engineering. More typically, they are used as a template for the fabrication of nanostructures if they serve, for instance, as a mask for deposition of new material on the surface on which particles are assembled or for etching of the material underneath; in this case, they are removed afterwards. This is what occurs in colloidal or nanosphere lithography. In some other cases, they are not used as a sacrificial material but they are incorporated in the final structure because they are inherently interesting for their properties. Independently of their specific use and application, different strategies have been devised in order to modify size and shape of colloidal particles, so as to enrich the variety of attainable patterns and to tailor the properties of the final structures and materials. In this review, we will focus on one of the most widespread methods to shape spherical colloidal particles, i.e. dry etching techniques. We will follow the development of such approaches until recent days, so as to trace an extensive panorama of the diverse parameters that can be harnessed to achieve specific morphological changes and highlight the characteristic features of the variants of this method. We will finally discuss how particles modified via dry etching can be used for patterning or can be resuspended in solvents for very diverse applications.

Electroless deposition of gold nanoparticles on carbon nanopipette electrode for electrochemical detection of catecholamines released from PC12 cells

An electroless deposition method is reported for the fabrication of gold nanoparticles (Au NPs) modified carbon nanopipette electrode (CNPE) for sensitive electrochemical detection of dopamine (DA) in aqueous solution and catecholamines released from PC12 cells. A CNPE is fabricated by chemical vapor deposition with a carbon layer onto nanocapillary and then contacted with copper (Cu) wire. Cu wire of CNPE is able to serve as reducing agent for electroless deposition of Au NPs on the CNPE because the potential of Cu²⁺/Cu is more negative than that of AuCl₄^-/Au. The method is simple, time-saving, and environmentally friendly. Field emission scanning electron microscopy, energy-dispersive X-ray analysis, and electrochemical techniques confirm the successful fabrication of the Au NPs/CNPE. Furthermore, Au NPs/CNPE exhibits a good sensing activity for DA oxidation with a wide linear determination range of 0.1-8 μmol/L and a low detection limit of 6 nmol/L. The Au NPs/CNPE can be potentially applied for measurement of catecholamines released from PC12 cells. This present work is believed to be beneficial to the design and development of active metal catalysts onto nanoelectrodes for the detection of electroactive biological molecules in living cells.Graphical abstract An electroless deposition method was developed for the fabrication of gold nanoparticles onto the carbon nanopipette electrode, which was served as an enhanced electrochemical sensing platform for highly sensitive detection of dopamine with a linear range of 0.1-8 μmol/L and a detection limit of 6 nmol/L, and was also applied in the detection of catecholamines released from PC12 cells.