Exceptional Light Sensitivity by Thiol-Ene Click Lithography.

Lithographic patterning, which utilizes the solubility switch of photoresists to convert optical signals into nanostructures on the substrate, is the primary top-down approach for nanoscale fabrication. However, the low light/electron-energy conversion efficiency severely limits the throughput of lithography. Thiol-ene reaction, as a photoinitiated radical addition reaction, is widely known as click reaction in the field of chemistry due to its extremely high efficiency. Here, we introduce a click lithography strategy utilizing the rapid thiol-ene click reaction to realize ultraefficient nanofabrication. This novel approach facilitated by the implementation of ultrahigh-functionality material designs enables high-contrast patterning of metal-containing nanoclusters under an extremely low deep-ultraviolet exposure dose, e.g., 7.5 mJ cm-2, which is 10-20 times lower than the dose used in the photoacid generator-based photoresist system. Meanwhile, 45 nm dense patterns were also achieved at a low dose using electron beam lithography, revealing the great potential of this approach in high-resolution patterning. Our results demonstrated the high-sensitivity and high-resolution features of click lithography, providing inspiration for future lithography design.

Charge Shielding-Oriented Design of Zinc-Based Nanoparticle Liquids for Controlled Nanofabrication.

Metal-containing nanoparticles possess nanoscale sizes, but the exploitation of their nanofeatures in nanofabrication processes remains challenging. Herein, we report the realization of a class of zinc-based nanoparticle liquids and their potential for applications in controlled nanofabrication. Utilizing the metal-core charge shielding strategy, we prepared nanoparticles that display glass-to-liquid transition behavior with glass transition temperature far below room temperature (down to -50.9 °C). Theoretical calculations suggest the outer surface of these unusual nanoparticles is almost neutral, thus leading to interparticle interactions weak enough to give them liquefaction characteristics. Such features endow them with extraordinarily high dispersibility and excellent film-forming capabilities. Twenty-two types of nanoparticles synthesized by this strategy have all shown good lithographic properties in the mid-ultraviolet, electron beam, or extreme ultraviolet light, and these nanoparticle liquids have achieved controlled top-down nanofabrication with predesigned 18 or 16 nm patterns. This proposed strategy is synthetically scalable and structurally extensible and is expected to inspire the design of entirely new forms of nanomaterials.

Process optimization of line patterns in extreme ultraviolet lithography using machine learning and a simulated annealing algorithm.

Resolution, line edge/width roughness, and sensitivity (RLS) are critical indicators for evaluating the imaging performance of resists. As the technology node gradually shrinks, stricter indicator control is required for high-resolution imaging. However, current research can improve only part of the RLS indicators of resists for line patterns, and it is difficult to improve the overall imaging performance of resists in extreme ultraviolet lithography. Here, we report a lithographic process optimization system of line patterns, where RLS models are first established by adopting a machine learning method, and then these models are optimized using a simulated annealing algorithm. Finally, the process parameter combination with optimal imaging quality of line patterns can be obtained. This system can control resist RLS indicators, and it exhibits high optimization accuracy, which facilitates the reduction of process optimization time and cost and accelerates the development of the lithography process.

Validation of reliable safe harbor locus for efficient porcine transgenesis.

Transgenic technology is now widely used in biomedical and agricultural fields. Transgenesis is commonly achieved through random integration which might cause some uncertain consequences. The site-specific integration could avoid this disadvantage. This study aimed to screen and validate the best safe harbor (SH) locus for efficient porcine transgenesis. First, the cells carrying the EGFP reporter construct at four different SH loci (ROSA26, AAVS1, H11 and COL1A1) were achieved through CRSIPR/Cas9-mediated HDR. At the COL1A1 and ROSA26 loci, a higher mRNA and protein expression of EGFP was detected, and it was correlated with a lower level of DNA methylation of the EGFP promoter, hEF1α. A decreased H3K27me3 modification of the hEF1α promoter at the COL1A1 locus was also detected. For the safety of transgenesis at different SH locus, we found that transgenesis could relatively alter the expression of the adjacent endogenous genes, but the influence was limited. We also did not observe any off-target cleavage for the selected sgRNAs of the COL1A1 and ROSA26 loci. In conclusion, the COL1A1 and ROSA26 were confirmed to be the best two SH loci with the COL1A1 being more competitive for porcine transgenesis. This work would greatly facilitate porcine genome engineering and transgenic pig production.

Ultrahigh-printing-speed photoresists for additive manufacturing.

Printing technology for precise additive manufacturing at the nanoscale currently relies on two-photon lithography. Although this methodology can overcome the Rayleigh limit to achieve nanoscale structures, it still operates at too slow of a speed for large-scale practical applications. Here we show an extremely sensitive zirconium oxide hybrid-(2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine) (ZrO2-BTMST) photoresist system that can achieve a printing speed of 7.77 m s-1, which is between three and five orders of magnitude faster than conventional polymer-based photoresists. We build a polygon laser scanner-based two-photon lithography machine with a linear stepping speed approaching 10 m s-1. Using the ZrO2-BTMST photoresist, we fabricate a square raster with an area of 1 cm2 in ~33 min. Furthermore, the extremely small chemical components of the ZrO2-BTMST photoresist enable high-precision patterning, leading to a line width as small as 38 nm. Calculations assisted by characterizations reveal that the unusual sensitivity arises from an efficient light-induced polarity change of the ZrO2 hybrid. We envisage that the exceptional sensitivity of our organic-inorganic hybrid photoresist may lead to a viable large-scale additive manufacturing nanofabrication technology.

Canny Algorithm Enabling Precise Offline Line Edge Roughness Acquisition in High-Resolution Lithography.

The line edge roughness (LER) is one of the most critical indicators of photoresist imaging performance, and its measurement using a reliable method is of great significance for lithography. However, most studies only investigate photoresist resolution and sensitivity because LER measurements require an expensive and not widely available critical dimension scanning electron microscopy (SEM) technology; thus, the imaging performance of photoresist has not been adequately evaluated. Here, we report an image processing software developed for offline calculation of LER that can analyze lithographic patterns with resolutions up to ∼15 nm. This software can effectively process all graphic files obtained from commonly used SEM machines by utilizing the adjustable double threshold. To realize the effective detection of high-resolution patterns in advanced lithography, we used SEM images generated from extreme ultraviolet and electron beam lithography to develop and validate the software's graphic recognition algorithm. This image processing software can process typical SEM images and produce reliable LER in an efficient and user-friendly manner, constituting a powerful tool for promoting the development of high-performance photoresist materials.

Theoretical Insights into the Solubility Polarity Switch of Metal-Organic Nanoclusters for Nanoscale Patterning.

Metal-organic nanoclusters(MOCs) are being increasingly used as prospective photoresist candidates for advanced nanoscale lithography technologies. However, insight into the irradiation-induced solubility switching process remains unclear. Hereby, the theoretical study employing density functional theory (DFT) calculations of the alkene-containing zirconium oxide MOC photoresists is reported, which is rationally synthesized accordingly, to disclose the mechanism of the nanoscale patterning driven by the switch of solubility from the acid-catalyzed or electron-triggered ligand dissociation. By evaluating the dependence of MOCs' imaging process on photoacid, lithographies of photoresists with and without photoacid generators after exposure to ultraviolet (UV), electron beam, and soft X-ray, it is revealed that photoacid is essential in UV lithography, but it demonstrates little effect on exposure dose in high-energy lithography. Furthermore, theoretical studies using DFT simulations to investigate the plausible photoacid-catalyzed, electron-triggered dissociation, and accompanying radical reaction are performed, and a mechanism is demonstrated that the nanoscale patterning of this type of MOCs is driven by the solubility switch resulting from dissociation-induced strong electrostatic interaction and low-energy barrier radical polymerization with other species. This study can give insights into the chemical mechanisms of patterning, and guide the rational design of photoresists to realize high resolution and high sensitivity.

Microwave-Assisted Air Epoxidation of Mixed Biolefins over a Spherical Bimetal ZnCo-MOF Catalyst.

Here, we report the synthesis of spherical bimetal ZnCo-MOF materials by a hydrothermal rotacrystallization method and their catalytic activity on the air epoxidation of mixed biolefins enhanced by microwaves. The structural and chemical properties of the ZnCo-MOF materials were fully characterized by XRD, IR, SEM, TG, XPS, and NH3-TPD. The morphology of the material exhibited a three-dimensional spherical structure. From an NH3-TPD test of the ZnCo-MOF catalyst, it could be concluded that the Zn0.1Co1-MOF-H-150 rpm material had the highest acidic content and the strongest acidity among the catalysts synthesized by different methods, which gave the best performance in the epoxidation of mixed biolefins. The air epoxidation reaction was carried out under atmospheric pressure and microwave conditions, in the absence of any initiator or coreducing agent. Moreover, the Zn0.1Co1-MOF catalyst could be recycled six times without reducing the catalytic activity significantly, which showed the stability of spherical catalyst material under microwaves.

Various hydrophilic carbon dots doped high temperature proton exchange composite membranes based on polyvinylpyrrolidone and polyethersulfone.

Novel organic-inorganic composite membranes were prepared conveniently by compositing of carbon dots (CDs) possessing different hydrophilicity into the low cost blended polymers of polyvinylpyrrolidone (PVP) and polyethersulfone (PES). The hydrophilicity of the CDs arises from its surface hydrophilic groups, which could be adjusted by controlling the reaction temperature and duration time. A series of homogeneous composite membranes doping with different hydrophilic CDs of up to about 10 wt% were obtained. Comprehensive characterizations were made in order to know the influence of different hydrophilic CDs on the properties of the prepared membranes. It is found that the doped CDs could cause the change in microphase separation and benefit proton conduction of the composite membranes. The more doped CDs, the higher the conductivity. A highest conductivity of 0.086 S cm-1 was reached by a composite membrane doped with both hydrophilic and hydrophobic CDs. Moreover, the incorporated CDs brought on the changes in properties of the composite membranes including free volume, hydrophilicity, acid doping level and swelling. A single fuel cell test was made based on the CDs blended membrane and indicating its potential to be used as the membrane electrolyte in high temperature proton exchange membrane fuel cells.

Microwave-activated Ni/carbon catalysts for highly selective hydrogenation of nitrobenzene to cyclohexylamine.

Biocarbon supported Ni catalysts have been prepared by facile impregnation of Ni species by microwave-heating and used for selective hydrogenation of nitrobenzene to cyclohexylamine. These catalysts were characterized by X-ray diffraction, Raman spectra, N2 sorption measurement, X-ray photoelectron spectroscopy, temperature programmed reduction of H2 and H2 temperature-programmed desorption. The morphology and particle size of catalysts were imaged by scanning electron microscope and transmission electron microscope. For the hydrogenation of nitrobenzene to cyclohexylamine, 10%Ni/CSC-II(b) exhibits the best catalytic activity to achieve 100 mol% conversion of nitrobenzene and 96.7% selectivity of cyclohexylamine under reaction conditions of 2.0 MPa H2 and 200 °C, ascribed to high dispersion of Ni species and formation of nanosized Ni particles on the support aided by microwave-heating. Thus-prepared Ni/CSC catalyst is greatly activated, in which the addition of precious metal like Rh is totally avoided.

Complete genome sequences of newcastle disease virus strains isolated from three different poultry species in china.

In 2000, three Newcastle disease virus (NDV) strains were isolated from outbreaks of infection in layers, ducklings, and geese in the same region of China during the same time period. Here, we report their complete genome sequences, which belong to the NDV genotype VIId. This discovery might provide clues as to the evolution of the NDVs of different avian origins.