Patterning optimization for device realization of patterned GaAsSbN nanowire photodetectors.

Vertically grown nanowires (NWs) are a research interest in optoelectronics and photovoltaic applications due to their high surface to volume ratio and good light trapping capabilities. This study presents the effects of process and design parameters on self-catalyzed GaAsSbN NWs grown by plasma-assisted molecular beam epitaxy on patterned silicon substrates using electron beam lithography. Vertical alignment of the patterned NWs examined via scanning electron microscopy show the sensitivity of patterned NW growth to the parameters of NW diameter, pitch, dose time, etching techniques and growth plan. Diameters range from 90 nm to 250 nm. Pitch lengths of 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, and 1200 nm were examined. Dry etching of the oxide layer of the silicon substrate and PMMA coating is performed using reactive ion etching (RIE) for 20 s and 120 s respectively. Comparisons of different HF etch durations performed pre and post PMMA removal are presented. Additionally, the report of an observed surfactant effect in dilute nitride GaAsSbN NWs in comparison to non-nitride GaAsSb is presented. Optimizations to patterning, RIE, and HF etching are presented to obtain higher vertical yield of patterned GaAsSbN NWs, achieving ∼80% of the expected NWµm2. Room temperature and 4 K photoluminescence results show the effect of nitride incorporation for further bandgap tuning, and patterned pitch on the optical characteristics of the NWs which gives insights to the compositional homogeneity for NWs grown at each pitch length.

Colloidal photonic crystal array chip based on nanoparticle self-assembly on patterned hydrophobic surface for signal-enhanced fluorescent assay of adenosine.

A controllable approach for preparing a portable colloidal photonic crystal (CPC) array chip is presented. The approach was inspired by the confinement effect of nanoparticle self-assembly on patterned surface. Hydrophobic polydimethylsiloxane substrate with reproducible micro-region array was fabricated by soft-lithography. The substrate was employed as the patterned template for self-assembly of monodisperse polystyrene nanoparticles. The CPC units can be prepared in several minutes, and exhibit consistent reflection wavelength. By adjusting the size of polystyrene nanoparticles and the shape of micro-regions, CPC units with multiple structure, colors and geometries were obtained. The CPC array chip features fluorescence enhancement owing to the optical modulation capability of the periodic nanostructure of the self-assembled CPC. With the reflection wavelength (523 nm) of green CPC units overlapping the emission wavelength (520 nm, with excitation wavelength of 490 nm) of 6-carboxyfluorescein-labeled DNA probe, the fluorescence intensity increased more than 10-fold. For signal-amplified assay of adenosine, the concentration range of linear response was 5.0 × 10-5 mol L-1 to 1.0 × 10-3 mol L-1, and the limit of detection was 1.3 × 10-6 mol L-1. Because of the enhancement effect of photonic crystal, the fluorescence images were more readable from the CPC array chip, compared with those from the planar substrate. The chip has potential applications in multiplex determination with high-throughput via encoding strategy based on the tunable structure, color or geometric shape. Graphical abstractSchematic diagram of signal-enhanced fluorescent detection of adenosine based on the colloidal photonic crystal array chip (PDMS, polydimethylsiloxane; PS NPs, polystyrene nanoparticles; CPC, colloidal photonic crystal; GO, graphene oxide; FAM, 6-carboxyfluorescein).

Immunomodulation and osseointegration activities of Na2TiO3 nanorods-arrayed coatings doped with different Sr content.

To endow Ti-based orthopedic implants immunomodulatory capability and thus enhanced osseointegration, different amounts of Sr are doped in Na2TiO3 nanorods in the arrays with identical nanotopographic parameters (rod diameter, length and inter-rod spacing) by substitution of Na+ using hydrothermal treatment. The obtained arrays are denoted as STSr2, STSr4, and STSr7, where the arabic numbers indicate the incorporating amounts of Sr in Na2TiO3. The modulation effects of the Sr-doped nanorods arrays on macrophage polarization and osteogenetic functions of osteoblasts are investigated, together with the array without Sr (ST). Moreover, osseointegration of these arrays are also assayed in rat femoral condyles. Sr-doped nanorods arrays accelerate M1 (pro-inflammatory phenotype)-to-M2 (anti-inflammatory phenotype) transformation of the adhered macrophages, enhancing secretion of pro-osteogenetic cytokines and growth factors (TGF-ß1 and BMP2), moreover, the Sr doped arrays directly enhance osteogenetic functions of osteoblasts. The enhancement of paracrine of M2 macrophages and osteogenetic function of osteoblasts is promoted with the increase of Sr incorporating amounts. Consequently, Sr doped arrays show significantly enhanced osseointegration in vivo compared to ST, and STSr7 exhibits the best performance. Our work sheds a new light on the design of surface chemical components and structures for orthopedic implants to enhance their osseointegration.

Multifaceted Biomedical Applications of Functional Graphene Nanomaterials to Coated Substrates, Patterned Arrays and Hybrid Scaffolds.

Because of recent research advances in nanoscience and nanotechnology, there has been a growing interest in functional nanomaterials for biomedical applications, such as tissue engineering scaffolds, biosensors, bioimaging agents and drug delivery carriers. Among a great number of promising candidates, graphene and its derivatives-including graphene oxide and reduced graphene oxide-have particularly attracted plenty of attention from researchers as novel nanobiomaterials. Graphene and its derivatives, two-dimensional nanomaterials, have been found to have outstanding biocompatibility and biofunctionality as well as exceptional mechanical strength, electrical conductivity and thermal stability. Therefore, tremendous studies have been devoted to employ functional graphene nanomaterials in biomedical applications. Herein, we focus on the biological potentials of functional graphene nanomaterials and summarize some of major literature concerning the multifaceted biomedical applications of functional graphene nanomaterials to coated substrates, patterned arrays and hybrid scaffolds that have been reported in recent years.

Growth of Single-Crystalline Cadmium Iodide Nanoplates, CdI2/MoS2 (WS2, WSe2) van der Waals Heterostructures, and Patterned Arrays.

Two-dimensional layered materials (2DLMs) have attracted considerable recent interest for their layer-number-dependent physical and chemical properties, as well as potential technological opportunities. Here we report the synthesis of two-dimensional layered cadmium iodide (CdI2) nanoplates using a vapor transport and deposition approach. Optical microscopy and scanning electron microscopy studies show that the resulting CdI2 nanoplates predominantly adopt hexagonal and triangular morphologies with a lateral dimension of ∼2-10 µm. Atomic force microscopy studies show that the resulting nanoplates exhibit a thickness in the range of 5-220 nm with a relatively smooth surface. X-ray diffraction studies reveal highly crystalline CdI2 in hexagonal phase, which is also confirmed by the characteristic Raman Ag mode at 110 cm-1. High-resolution transmission electron microscopy and selected area electron diffraction reveal that the resulting CdI2 nanoplates are single crystals. Taking a step further, we show the CdI2 nanoplates were readily grown on other 2DLMs (e.g., WS2, WSe2, MoS2), forming diverse van der Waals heterostructures. Using prepatterned WS2 monolayer square arrays as the nucleation and growth templates, we also show that regular arrays of CdI2/WS2 vertical heterostructures can be prepared. The synthesis of the CdI2 nanoplates, heterostructures, and heterostructure arrays offers a valuable material system for 2D materials science and technology.