Sorting Gold and Sand (Silica) Using Atomic Force Microscope-Based Dielectrophoresis

Additive manufacturing–also known as 3D printing–has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures. However, the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir, which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle. Here, we propose a dielectrophoresis (DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork (QTF)-atomic force microscope (AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions. We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation, which confirmed the surface-enhanced Raman spectroscopy (SERS). To validate the scheme, we also performed a simulation for the system and found qualitative agreement with the experimental results. The method that combines DEP, pipette-based AFM, and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning, materials sorting, and diverse advanced applications. "Image missing"

Enhancing Photocatalytic Hydrogen Production of g-C3N4 by Selective Deposition of Pt Cocatalyst

Graphitic carbon nitride (g-C3N4) has been widely studied as a photocatalyst for the splitting of water to produce hydrogen. In order to solve the problems of limited number of active sites and serious recombination rate of charge-carriers, noble metals are needed as cocatalysts. Here, we selectively anchored Pt nanoparticles (NPs) to specific nitrogen species on the surface of g-C3N4 via heat treatment in argon–hydrogen gas mixture, thus achieving g-C3N4 photocatalyst anchored by highly dispersed homogeneous Pt NPs with the co-existed metallic Pt0 and Pt2+ species. The synergistic effect of highly dispersed metallic Pt0 and Pt2+ species makes the catalyst exhibit excellent photocatalytic performance. Under the full-spectrum solar light irradiation, the photocatalytic hydrogen production rate of the photocatalyst is up to 18.67 mmol·g−1·h−1, which is 5.1 times of the catalyst prepared by non-selective deposition of Pt NPs.

SELECTIVE DEPOSITION OF NANOFIBERS NET ON TEXTILE STRUCTURES

Nanotechnology has evolved in the last years and nowadays there are many technologies related with the development of nanoparticles (NPs) or nanofibers (NFs). Due to the wide variety of polymers and diverse applications, filtration, medicine, cosmetic, etc., the study of those NFs is still of interest nowadays. In this work the NFs net created from electrospinning is used as a coating for fabrics. The aim of this work is to demonstrate how fibres are placed on the fabrics and if there is a tendency or they are located randomly. Two different fabrics were used a 100 % cotton plain 115g/m2 and a 100% polyamide knitting fabric 60 g/m2. A PVA solution (9% w/v) was used to create NFs which were placed on the fabrics. This solution was prepared by heating water at 80º C till complete solution of the polymer. Electrospinning was designed for a vertical collector with 15 cm distance from the needle. The flow rate was 0,5 mL/h with 15 or 20 kV for 15 minutes. Results evidenced the tendency of NFs net to be located on the fibres and consequently we could conclude the fabric is designing the position where the fibres would be placed. Furthermore, we could demonstrate that the presence of a fabric with reduced density implies deposition of NFs on both the fabric and the collector.