Microfluidic paper-based analytical devices (μPADs) are a growing class of low-cost chemo/biosensing technologies designed for point-of-use applications. In this article, we describe MTWP (movable-type wax printing), a facile method for the fabrication of μPADs. MTWP is inspired by the Chinese movable-type printing and requires only a hot plate and homemade small iron movable components. It is able to pattern various wax microstructures in paper via a simple adjustment of the number, patterning forms or types of the metal movable components. This inexpensive and versatile method may thus hold great potential for producing wax-patterned μPADs by untrained operators at minimized cost in developing countries. In addition, two novel equipment-free assay methods are further developed to render μPAD measurements straightforward and quantitative. They use the flow-through time of a detection reagent in a three-dimensional paper device and the number of colored detection microzones in a 24-zone paper device as the detection motifs. The timing method is based on the selective wettability change of paper from hydrophilic to hydrophobic that is mediated by enzymatic reactions. The counting method is carried out on the basis of oxidation-reduction reactions of a colored substance, namely iodine. Their utility is demonstrated with quantitative detection of hydrogen peroxide as a model analyte. These methods require only a timer or a cell phone with a timing function and the abilities of seeing color and of counting for quantitative μPAD measurement, thus making them simple, cost-efficient, and useful sensor technologies for a great diversity of point-of-need applications especially in resource-poor settings.

Silicon holds great promise as an anode material for lithium-ion batteries with higher energy density; its implication, however, is limited by rapid capacity fading. A catalytic growth of graphene cages on composite particles of magnesium oxide and silicon, which are made by magnesiothermic reduction reaction of silica particles, is reported herein. Catalyzed by the magnesium oxide, graphene cages can be conformally grown onto the composite particles, leading to the formation of hollow graphene-encapsulated Si particles. Such materials exhibit excellent lithium storage properties in terms of high specific capacity, remarkable rate capability (890 mAh g at 5 A g ), and good cycling retention over 200 cycles with consistently high coulombic efficiency at a current density of 1 A g . A full battery test using LiCoO as the cathode demonstrates a high energy density of 329 Wh kg .

Multisegment PtNi nanorods (Ni−Pt, Ni−Pt−Ni, Ni−Pt−Ni−Pt, and Ni−Pt−Ni−Pt−Ni) with controllable lengths of the individual metals were obtained by sequential electrodeposition of the metals into the pores of anodic aluminum oxide (AAO) membranes. Field emission scanning electron microscopy (FESEM) showed that the nanorods are about 170 nm in diameter and 1.6 μm in length, with 530 nm of total Pt segment lengths. The alternating Pt and Ni segments could be easily differentiated by FESEM. XRD characterization of the PtNi nanorods indicated that both Pt and Ni are polycrystals with a face-centered cubic structure. The presence of Pt(0), Pt(II), Pt(IV), Ni(0), and Ni(II) on the surface of the PtNi nanorods was deduced from XPS measurements. The nanorods are catalytically active in the room temperature electro-oxidation of methanol. The relative rates of reaction as recorded by cyclic voltammetry showed a linear relationship between the peak current densities and the number of Pt−Ni interfaces. The use of segmented nanorods with identifiable Pt−Ni interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts and has provided a direct demonstration of the role of pair sites in the bifunctional mechanism.

A novel colorimetric assay was established based on folic acid-conjugated porous Pd@Au nanoparticles possessing peroxidase-like activity as labels for the rapid detection of human chronic myelogenous leukemia cell lines (K-562).