The layered two-dimensional (2D) materials, e.g., the well-known graphene, transition metal dichalcogenides, and topological insulators, have attracted great interest of researchers from fundamental research as well as industries owing to their intriguing properties in a number of aspects. In practical applications, the efficient modification of the features of 2D materials is compelling and essential to achieve desired functionalities. Ion implantation has been successfully applied to synthesize graphene. The most exotic advantage of ion beam technology is that it offers distinct options of energetic beams, which has recently shown the unique capability to modify and tailor the properties of versatile 2D materials. To name a few, the energetic ion beams could implement the surface morphology or layer-to-layer structural engineering of 2D materials. At the microcosmic level, the introduction of ion beam induced defects and intentional doping of specific ions are the basis of tailoring properties of 2D mat...

Ion beam modification of two-dimensional materials: Characterization, properties, and applications

Thermoelectrics can directly harvest electricity from waste heat through the Seebeck effect, therefore it has been regarded as an eco-friendly and sustainable solution to alleviate the pressure from fossil fuel consumption and environmental pollution. Rational structural manipulation is critical to improving the thermoelectric performance of materials, and a timely review is required to summarize the recent progress on the novel structural design for thermoelectrics. In this review, taking SnSe as a typical example and combined with other thermoelectric materials, we summarize recent advances in the rational structural manipulation for thermoelectric materials, including point defects, dislocations, boundaries, nanoinclusions, and nanopores. The inherent links between syntheses, characterizations, and thermoelectric properties by tailoring the structures are established. In addition, we discuss the development of nanoscale thermoelectric materials and their potential for applying to flexible thermoelectric devices. This review can guide the design of high-performance thermoelectric materials.

Rational Structure Design and Manipulation Advance SnSe Thermoelectrics

Ligase and polynucleotide kinase (PNK) play important roles in DNA repair process. In this work, a simple, convenient and ultrasensitive fluorescence biosensor for label-free detection of ligase and PNK was proposed on the basis of target-triggered hyper-branched rolling circle amplification (HRCA). In the presence of PNK and ligase, the 5′-OH end of a linear Padlock DNA strand could be phosphorylated by PNK and then be converted by ligase into a circular template to trigger subsequent exponential HRCA reaction, producing amounts of double-stranded DNA (dsDNA) fragments, accompanied by the significant fluorescence increase of dsDNA-intercalating dye–SYBR Green I (SG I). In the absence of ligase or PNK, however, HRCA primer and uncyclized Padlock strands were completely digested by exonucleases, thus providing a low background for the sensing system. Therefore, by recording the fluorescence change of SG I, ligase and PNK activity could be facilely determined. The proposed biosensor exhibited excellent detection sensitivity for ligase and PNK activity with the detection limits of 3.4 × 10−4 U/mL and 3.8 × 10−4 U/mL, respectively. Such a sensing strategy could be easily extended to studies on inhibitors of these two enzymes, thus might offer a promising tool in clinical molecular diagnostics and cancer therapy.

Ultrasensitive, label-free detection of T4 ligase and T4 polynucleotide kinase based on target-triggered hyper-branched rolling circle amplification

As a vital enzyme in DNA phosphorylation and restoration, T4 polynucleotide kinase (T4 PNK) has aroused great interest in recent years. Therefore, numerous strategies have been established for highly sensitive detection of T4 PNK based on diverse signal amplification techniques. However, they often need sophisticated design, a variety of auxiliary reagents and enzymes, or cumbersome manipulations. We have designed a new kind of allosteric aptamer probe (AAP) consisting of streptavidin (SA) aptamer and the complementary DNA (cDNA) for simple detection of T4 PNK without signal amplification and with minimized interference in complex biological samples. When the 5′-terminus of the cDNA is phosphorylated by T4 PNK, the cDNA is degraded by lambda exonuclease to release the fluorescein amidite (FAM)-labeled SA aptamer, which subsequently binds to streptavidin beads. The enhancement of the fluorescence signal on SA beads can be detected precisely and easily by a microscope or flow cytometer. Our method performs ...

Detection of T4 Polynucleotide Kinase via Allosteric Aptamer Probe Platform.

Structure and electron field emission properties of ion beam reduced graphene oxide sheets

A novel naked-eye distinguishable nanosensor based on phosphorylation triggered poly-nanoparticle assembly strategy has been designed for detecting T4 PNK activity. This colorimetric sensor exhibits conveniently homogeneous operation with simple, sensitive and easily scalable properties.

Phosphorylation triggered poly-nanoparticle assembly for naked-eye distinguishable T4 polynucleotide kinase detection

Immediate fabrication of flower-like graphene oxide by ion beam bombardment

We evaluate the influence of pressure on the thermoelectric power factors PF ≡ S2σ of pristine and Na-doped SnSe crystals by measuring their electrical conductivity σ(T) and Seebeck coefficient S(T) up to ∼22 kbar with a self-clamped piston-cylinder cell. For both cases, σ(T) is enhanced while S(T) reduced with increasing pressure as expected, but their imbalanced variations lead to a monotonic enhancement of PF under pressure. For pristine SnSe, σ(290 K) increases by ∼4 times from ∼10.1 to 38 S cm−1, while S(290 K) decreases by only ∼12% from 474 to 415 μV K−1, leading to about three-fold enhancement of PF from 2.24 to 6.61 μW cm−1 K−2, which is very close to the optimal value of SnSe above the structural transition at ∼800 K at ambient pressure. In comparison, the PF of Na-doped SnSe at 290 K is enhanced moderately by ∼30% up to 20 kbar. In contrast, the PF of isostructural black phosphorus with a simple band structure was found to decrease under pressure. The comparison with black phosphorus indicates that the multi-valley valence band structure of SnSe is beneficial for the enhancement of PF by retaining a large Seebeck coefficient under pressure. Our results also provide experimental confirmation on the previous theoretical prediction that high pressure can be used to optimize the thermoelectric efficiency of SnSe.

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Junjie Cheng

Papers

Phosphorylation triggered poly-nanoparticle assembly for naked-eye distinguishable T4 polynucleotide kinase detection

Immediate fabrication of flower-like graphene oxide by ion beam bombardment

Pressure-induced enhancement of thermoelectric power factor in pristine and hole-doped SnSe crystals