The fabrication of ultrasmall nanogaps (sub‐1 nm) with high density is of significant interest and importance in physics, chemistry, life science, materials science, surface science, nanotechnology, ...and environmental engineering. However, it remains a challenge to generate uncovered and clean sub‐1‐nm gaps with high density and uniform reproducibility. Here, a facile and low‐cost approach is demonstrated for the fabrication of high‐density sub‐1‐nm gaps from Au nanoparticle monolayers as reproducible surface‐enhanced Raman scattering (SERS) substrates. Au nanoparticles with larger diameters possess lower surface charge, thus the obtained large‐area nanoparticle monolayer generates a high‐density of sub‐1‐nm gaps. In addition, a remarkable SERS performance with a 1011 magnitude for the Raman enhancement is achieved for 120 nm Au nanoparticle monolayers due to the dramatic increase in the electromagnetic field enhancement when the obtained gap is smaller than 0.5 nm. The Au nanoparticle monolayer is also transferred onto a stretchable PDMS substrate and the structural stability and reproducibility of the high‐density sub‐1‐nm gaps in Au monolayer films are illustrated. The resultant Au nanoparticle monolayer substrates with an increasing particle diameter exhibit tunable plasmonic properties, which control the plasmon‐enhanced photocatalytic efficiency for the dimerization of p‐aminothiophenol. The findings reported here offer a new opportunity for expanding the SERS application.
A facile and low‐cost approach is demonstrated for the fabrication of high‐density sub‐1‐nm gaps from Au nanoparticle monolayers as reproducible surface‐enhanced Raman scattering (SERS) substrates. Remarkable SERS performance with a 1011 magnitude Raman enhacement is achieved for 120 nm Au nanoparticle monolayers due to the dramatic increase in the electromagnetic field enhancement when the obtained gap is smaller than 0.5 nm.
The stability of single-atom catalysts is critical for their practical applications. Although a high temperature can promote the bond formation between metal atoms and the substrate with an enhanced ...stability, it often causes atom agglomeration and is incompatible with many temperature-sensitive substrates. Here, we report using controllable high-temperature shockwaves to synthesize and stabilize single atoms at very high temperatures (1,500-2,000 K), achieved by a periodic on-off heating that features a short on state (55 ms) and a ten-times longer off state. The high temperature provides the activation energy for atom dispersion by forming thermodynamically favourable metal-defect bonds and the off-state critically ensures the overall stability, especially for the substrate. The resultant high-temperature single atoms exhibit a superior thermal stability as durable catalysts. The reported shockwave method is facile, ultrafast and universal (for example, Pt, Ru and Co single atoms, and carbon, C
N
and TiO
substrates), which opens a general route for single-atom manufacturing that is conventionally challenging.
Aptamers have been widely used as recognition elements for biosensor construction, especially in the detection of proteins or small molecule targets, and regarded as promising alternatives for ...antibodies in bioassay areas. In this review, we present an overview of reported design strategies for the fabrication of biosensors and classify them into four basic modes: target-induced structure switching mode, sandwich or sandwich-like mode, target-induced dissociation/displacement mode and competitive replacement mode. In view of the unprecedented advantages brought about by aptamers and smart design strategies, aptamer-based biosensors are expected to be one of the most promising devices in bioassay related applications.
Color vision: Multicolor molecular beacons are constructed from relatively large gold nanoparticles self‐assembled with stem–loop probes and helper oligonucleotides (see picture). The nanobeacons can ...respond differentially to multiple DNA targets, emitting multiple colors.
Surface-layer defects of M-plane sapphire caused by ultrasonic vibration-assisted cutting were investigated in this paper through comparison cutting experiments. Topography analysis results indicate ...that when the cutting direction is not along a-axis or c-axis, the spalling defects of conventional cutting groove are asymmetric because the probabilities of activated cleavage/twinning systems vary with machining direction; however, the vibrational cutting groove presents better symmetry and less spalling owning to the propagation of stress wave. The cross-section of cutting groove was obtained by focus ion beam cutting. The cross-section analysis shows that the subsurface defects of conventional cutting groove involve median cracks and lateral cracks, and the main propagating path of cracks is towards downward, which is the cause of the generation of serious spalling; however, lateral cracks are the main defect in the subsurface of the vibrational cutting groove, and they mainly propagate towards the free surface and give rise to material removal. The subsurface quality of cutting groove with ultrasonic assistance is better than that of the conventional cutting groove. It is evident that ultrasonic vibration can prevent the median crack from extending towards bulk material and contribute to improve the uniformity of groove quality.
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•Crystal indices are considered in computing the probability of deformation system.•Subsurface defects are more serious in traditional cutting groove.•Vibration-assisted cutting improves the uniformity of groove quality.•Ultrasonic vibration can prevent median crack from extending in bulk material.
The influences of morphology and thickness of zinc oxide (ZnO) buffer layers on the performance of inverted polymer solar cells are investigated. ZnO buffer layers with different morphology and ...thickness varying from several nanometers to ≈55 nm are fabricated by adjusting the concentration of the precursor sol. The ZnO buffer layers with nearly same surface quality but with thickness varying from ≈7 to ≈65 nm are also fabricated by spinning coating for comparison. The photovoltaic performance is found to be strongly dependent on ZnO surface quality and less dependent on the thickness. The use of dense and homogenous ZnO buffer layers enhances the fill factor and short‐circuit current of inverted solar cell without sacrificing the open‐circuit voltage of device due to an improvement in the contact between the ZnO buffer layer and the photoactive layer. Inverted devices with a dense and homogenous ZnO buffer layer derived from 0.1 M sol exhibit an overall conversion efficiency of 3.3% which is a 32% increase compared to devices with a rough ZnO buffer layer made from 1 M sol, which exhibited a power conversion efficiency of 2.5%. The results indicate that the efficiency of inverted polymer solar cells can be significantly influenced by the morphology of the buffer layer.
Inverted devices with a dense and homogenous ZnO buffer layer derived from 0.1 M sol exhibit an overall conversion efficiency of 3.3%, which is a 32% increase compared to the power conversion efficiency of 2.5% for devices with a rough ZnO buffer layer made from 1 M sol. The results indicate that the efficiency of inverted polymer solar cells can be significantly influenced by the morphology of the buffer layer.
Considering manufacturing errors and installation errors in the automatic battery replacement system, it is necessary to analyze the uncertainty of the automatic battery replacement system to improve ...the efficiency and accuracy of the system. There are a few universal approaches for uncertainty analysis, such as interval analysis, probability analysis, and combination approach. This paper uses grey number theory, a relatively new method, to analyze. The analysis on the coordinates of the support points finds that the grey number theory can output a range smaller than that of the other three methods, and its results are in line with the actual situation. The grey number theory is used to analyze the coordinate position change of the support point of the automatic battery replacement device with the input error change and the driving rod angle change. The bar tolerance and error circle (installation error) existing in the system are also taken into consideration. Comparing the results produced by the case where error circle is considered and that is not, it can be seen that the influence of the error circle on the results is relatively insignificant compared with that of rod tolerance, but the influence cannot be ignored for structures requiring high precision. Therefore, the analysis of the input error percentage can yield a reasonable control range of the input error based on the grey number theory, which not only ensures the system is safe and reliable, but also is cost-efficient.
Ionic porous organic polymers have attracted much attention due to their broad applications in catalysis, energy storage/conversion, proton conduction, etc. In this paper, an ionic porous organic ...polymer, CMP‐PM‐Me, was synthesized through post‐synthetic modification of a pyrimidine‐based conjugated microporous polymer, CMP‐PM, which was constructed by the palladium catalyzed Sonogashira reaction of 1,3,5‐triethynylbenzen and 2,5‐dibromopyrimidine. These two polymers are porous with Brunauer–Emmett–Teller surface areas of 416 and 241 m2 g−1 for CMP‐PM and CMP‐PM‐Me, respectively. Due to the cationic framework, CMP‐PM‐Me exhibits a much faster and more efficient adsorption performance to anionic dyes such as Congo red (CR) and methyl orange (MO) than that of CMP‐PM with a neutral framework. The uptakes for CR are 400.0 mg g−1 for CMP‐PM‐Me and 344.8 mg g−1 for CMP‐PM, respectively. Furthermore, CMP‐PM‐Me could quickly and drastically separate anionic dyes from the binary mixed solution of anionic and nonanionic dyes within a short time. This work not only enriches the family of ionic organic porous polymers and widens their synthetic utility, but also demonstrates their applications in the adsorption and separation of anionic dyes in water.
Work on water: An ionic conjugated microporous polymer based on pyrimidine has been synthesized by post‐cationic modification. It exhibits ultrafast adsorption and separation of anionic dyes in water (see figure).
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