Two-step Synthesis Strategy Research Articles

Hybrid single/poly-crystalline ZnO nanoawl arrays: facile synthesis and enhanced field emission properties

Arrays of hybrid single/poly-crystalline ZnO nanoawls (HSP-ZNAs) composed of single-crystalline ZnO nanorod (ZNR) holders and poly-crystalline nanoneedles were for the first time fabricated via a facile two-step synthesis strategy that was based on firstly an aqueous electrodeposition and secondly an aqueous chemical growth (ACG). The two-step synthesis strategy not only can ensure reliable electrical contact between the ZNR holders and the substrates, but also can afford control over the crystal structure and aspect ratio of the nanoneedles. The as-grown HSP-ZNA arrays exhibited markedly enhanced field emission (FE) current at lower electric fields compared with the whole single-crystalline ZNA arrays or ZNR arrays without nanoneedles. The improvement could be attributed to more emission sites from the tips of poly-crystalline nanoneedles of the HSP-ZNAs. Our results demonstrate the HSP-ZNA arrays one of the promising candidates for FE devices, and also provide a new paradigm for synthesizing novel hybrid single/poly-crystalline nanostructures that could find many potential applications in electronics and optoelectronics.

A Multifunctional Organic–Inorganic Hybrid Structure Based on MnIII–Porphyrin and Polyoxometalate as a Highly Effective Dye Scavenger and Heterogenous Catalyst

A two-step synthesis strategy has led to a unique layered polyoxometalate-Mn(III)-metalloporphyrin-based hybrid material. The hybrid solid demonstrates remarkable capability for scavenging of dyes and for heterogeneous selective oxidation of alkylbenzenes with excellent product yields and 100% selectivity.

Enhanced photocatalytic activity of hierarchical ZnO nanoplate-nanowire architecture as environmentally safe and facilely recyclable photocatalyst

A hierarchical ZnO nanoplate-nanowire (ZNP-ZNW) architecture immobilized onto a substrate via a facile two-step synthesis strategy was used as an environmentally safe and recyclable photocatalyst. It showed greatly enhanced photocatalytic activity compared with a monomorphological ZnO nanoplate structure in the degradation of methyl orange (MO). The higher content of surface oxygen defects, which can capture the photogenerated electrons and holes separately and make them available for decomposing organic contaminants, is considered to play an important role in the degradation of MO and makes a major contribution to the enhanced photocatalysis. Increasing the surface-to-volume (S/V) ratio without limit cannot benefit the photocatalytic activity significantly if there are not enough defects to separate additional photogenerated charges caused by a larger S/V ratio. A detailed photocatalytic mechanism related to surface defects of the hierarchical architecture was clearly demonstrated. The present study provides a new paradigm for further understanding the photocatalytic mechanism and suggests a new direction to design high-efficiency photocatalysts based on increasing the number of surface defects of nanostructures.

Fluorine-Ion-Mediated Electrodeposition of Rhombus-Like ZnFOH Nanorod Arrays: An Intermediate Route to Novel ZnO Nanoarchitectures

Novel rhombus-like ZnO nanorod (NR) arrays were achieved via a facile two-step synthesis strategy based on first a low-temperature aqueous electrodeposition of vertically aligned rhombic ZnFOH NR arrays in the presence of fluoride and second a pyrolysis of ZnFOH intermediate into ZnO with the same morphology. The fluorine-ion-mediated electrodeposition mechanism of ZnFOH was confirmed for the first time, and the proposed formation process that the rhombus-like ZnO NRs characterized by mesoporous structure derived from the electrodeposited ZnFOH intermediate was corroborated by systematic structural characterization of the as-prepared products. A dye-sensitized solar cell (DSSC) based on the rhombus-like ZnO NR arrays with a larger surface roughness factor was assembled, and a higher conversion efficiency of 0.69% was attained in comparison to 0.47% of the DSSC based on the hexagon-like ZnO NR arrays electrodeposited in the absence of fluoride. Further, we demonstrate that the unique two-step synthesis strategy also possessed the capability of constructing complex nanoarchitectures with 1D rhombus-like ZnO NRs as the building blocks.

Codon optimization through a two-step gene synthesis leads to a high-level expression of Aspergillus niger lip2 gene in Pichia pastoris

Aspergillus niger lipases are important biocatalysts for a broad range of industrial applications. To enhance the expression level of a newly cloned lipase gene lip2 of A. niger in Pichia pastoris, we applied codon optimization and synthesized the full length codon-optimized gene by a two-step gene synthesis strategy. This strategy consists of an assembly PCR for several small DNA fragments and enzymatic digestion and ligation steps to ligate these fragments into the full-length gene. First, the full-length lip2 gene was divided into three fragments F1 (237 bp), F2 (238 bp) and F3 (422 bp) with the additions of proper restriction sites, and separately amplified by assembly PCR reactions. Second, three PCR amplified fragments were digested and ligated into the full-length lip2 gene. In the two-step gene synthesis, synthesis of smaller DNA fragments resulted in a significant lower level of nonspecific mismatching among oligonucleotides and a very low mutational rate of the PCR products, demonstrating the superiority of the method. When compared with the originally cloned lip2 gene of A. niger, the new codon optimized lip2 gene expressed at a significantly higher level in yeasts after methanol induction for 72 h, and both the enzyme activity and protein content reached maximal levels of 191 U/ml and 154 mg/1, with 11.6- and 5.3-fold increases, respectively.

A general two-step strategy to synthesize lariat RNAs

We describe a general and efficient two-step strategy for lariat RNA synthesis. In the first step, a deoxyribozyme synthesizes 2',5'-branched RNA. In the second step, T4 RNA ligase closes the loop that completes the lariat. The loop-closure reaction can form either a natural or unnatural lariat isomer, depending on which of the two 3'-termini of the branched RNA reacts with the lone 5'-end. We demonstrate two approaches to control formation of either lariat isomer. In conjunction with other routes for lariat RNA synthesis, the two-step strategy described here will facilitate biochemical studies that require lariat RNAs of varying nucleotide sequence.