Machine learning-guided synthesis of advanced inorganic materials

Synthesis of advanced inorganic materials with minimum number of trials is of paramount importance towards the acceleration of inorganic materials development. The enormous complexity involved in existing multi-variable synthesis methods leads to high uncertainty, numerous trials and exorbitant cost. Recently, machine learning (ML) has demonstrated tremendous potential for material research. Here, we report the application of ML to optimize and accelerate material synthesis process in two representative multi-variable systems. A classification ML model on chemical vapor deposition-grown MoS2 is established, capable of optimizing the synthesis conditions to achieve higher success rate. While a regression model is constructed on the hydrothermal-synthesized carbon quantum dots, to enhance the process-related properties such as the photoluminescence quantum yield. Progressive adaptive model is further developed, aiming to involve ML at the beginning stage of new material synthesis. Optimization of the experimental outcome with minimized number of trials can be achieved with the effective feedback loops. This work serves as proof of concept revealing the feasibility and remarkable capability of ML to facilitate the synthesis of inorganic materials, and opens up a new window for accelerating material development

Laser-assisted synthesis of two-dimensional transition metal dichalcogenides: a mini review

The atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted the researcher’s interest in the field of flexible electronics due to their high mobility, tunable bandgaps, and mechanical flexibility. As an emerging technique, laser-assisted direct writing has been used for the synthesis of TMDCs due to its extremely high preparation accuracy, rich light–matter interaction mechanism, dynamic properties, fast preparation speed, and minimal thermal effects. Currently, this technology has been focused on the synthesis of 2D graphene, while there are few literatures that summarize the progress in direct laser writing technology in the synthesis of 2D TMDCs. Therefore, in this mini-review, the synthetic strategies of applying laser to the fabrication of 2D TMDCs have been briefly summarized and discussed, which are divided into top-down and bottom-up methods. The detailed fabrication steps, main characteristics, and mechanism of both methods are discussed. Finally, prospects and further opportunities in the booming field of laser-assisted synthesis of 2D TMDCs are addressed

Inverse design and realization of an optical cavity-based displacement transducer with arbitrary responses

Optical cavity has long been critical for a variety of applications ranging from precise measurement to spectral analysis. A number of theories and methods have been successful in describing the optical response of a stratified optical cavity, while the inverse problem, especially the inverse design of a displacement sensitive cavity, remains a significant challenge due to the cost of computation and comprehensive performance requirements. This paper reports a novel inverse design methodology combining the characteristic matrix method, mixed-discrete variables optimization algorithm, and Monte Carlo method-based tolerance analysis. The material characteristics are indexed to enable the mixed-discrete variables optimization, which yields considerable speed and efficiency improvements. This method allows arbitrary response adjustment with technical feasibility and gives a glimpse into the analytical characterization of the optical response. Two entirely different light-displacement responses, including an asymmetric sawtooth-like response and a highly symmetric response, are dug out and experimentally achieved, which fully confirms the validity of the method. The compact Fabry-Perot cavities have a good balance between performance and feasibility, making them promising candidates for displacement transducers. More importantly, the proposed inverse design paves the way for a universal design of optical cavities, or even nanophotonic devices

Enhancing the Toughness of Free-Standing Polyimide Films for Advanced Electronics Applications: A Study on the Impact of Film-Forming Processes

High-quality and free-standing polyimide (PI) film with desirable mechanical properties and uniformity is in high demand due to its widespread applications in highly precise flexible and chip-integrated sensors. In this study, a free-standing PI film with high toughness was successfully prepared using a diamine monomer with ether linkages. The prepared PI films exhibited significantly superior mechanical properties compared to PI films of the same molecular structure, which can be attributed to the systematic exploration of the film-forming process. The exploration of the film-forming process includes the curing procedures, film-forming substrates, and annealing treatments. Additionally, the thickness uniformity and surface homogeneity of free-standing films were crucial for toughness. Increasing the crystallinity of the PI films by eliminating residual stress also contributed to their high strength. The results demonstrate that by adjusting the above-mentioned factors, the prepared PI films possess excellent mechanical properties, with tensile strength and elongation at break of 194.71 MPa and 130.13%, respectively

Size‐dependent activity of iron‐nickel oxynitride towards electrocatalytic oxygen evolution

The exploration of efficient nonprecious metal‐based oxygen evolution reaction (OER) electrocatalysts is of great significance. Herein, both size‐ and component‐tuned FeNi oxynitride are prepared and employed for electrocatalytic water oxidation. Combining the excellent metal‐like feature of induced OER activity of nitrides and oxidation resistance performance of oxides, the obtained FeNi oxynitride delivers an outstanding OER performance. The synergistic interplay between Fe, Ni components creates a favorable local coordination environment for OER and decreased sizes enables more active sites exposure. As a result, under 1 M KOH, the optimized material displays highly efficient electrocatalytic OER performance with low overpotential 295 mV (10 mA cm−2 catalytic current density) and considerable durability. These findings open up opportunities to explore other excellent catalysts through multicomponent strong interactions coupled with size control.This work was financially supported by the National NaturalScience Foundation of China (Nos. 21606113 and 21676128),and the International Postdoctoral Exchange Fellowship byChina Postdoctoral Science Foundation (No. 20170055)

2D Cairo pentagonal PdPS : air-stable anisotropic ternary semiconductor with high optoelectronic performance

Pentagonal 2D materials as a new member in the 2D material family have attracted increasing attention due to the exotic physical properties originating from the unique Cairo pentagonal tiling topology. Herein, the penta-PdPS atomic layers as a new air-stable 2D semiconductor with the unique puckered pentagonal low-symmetry structure are successfully exfoliated from bulk crystals grown via chemical vapor transport (CVT). Notably, 2D pentaPdPS exhibits outstanding electronic and optoelectronic performance under 650 nm laser: high electron mobility of ≈208 cm2 V−1 s−1, an ultrahigh on/off ratio of ≈108, a high photoresponsivity of 5.2 × 104 A W−1, a high photogain of 1.0 × 105, an ultrahigh detectivity of 1.0 × 1013 Jones, respectively. Significantly, the exceptional puckered pentagonal atomic structure of 2D PdPS makes it strong in-plane anisotropy in optical, electronic, and optoelectronic properties, demonstrating a sizeable anisotropic ratio of carrier mobility and photocurrent with the value of up to 3.9 and 2.3, respectively. These excellent properties make 2D Cairo Pentagonal PdPS a potential candidate in nanoelectronics, optoelectronics, polarized-nanoelectronics, which will significantly promote the development of 2D materials.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Z.L. acknowledges supports from Singapore National Research Foundation – Competitive Research Program NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007. This research was also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052)

PdPSe : component-fusion-based topology designer of two-dimensional semiconductor

Novel 2D semiconductors play an increasingly important role in modern nanoelectronics and optoelectronics. Herein, a novel topology designer based on component fusion is introduced, featured by the submolecular component integration and properties inheritance. As expected, a new air-stable 2D semiconductor PdPSe with a tailored puckered structure is successfully designed and synthesized via this method. Notably, the monolayer of PdPSe is constructed by two sublayers via PP bonds, different from 2D typical transition metal materials with sandwich-structured monolayers. With the expected orthorhombic symmetry and intralayer puckering, PdPSe displays a strong Raman anisotropy. The field-effect transistors and photodetectors based on few-layer PdPSe demonstrate good electronic properties with high carrier mobility of ≈35 cm2 V−1 s−1 and a high on/off ratio of 106, as well as excellent optoelectronic performance, including high photoresponsivity, photogain, and detectivity with values up to 1.06 × 105 A W−1, 2.47 × 107%, and 4.84 × 1010 Jones, respectively. These results make PdPSe a promising air-stable 2D semiconductor for various electronic and optoelectronic applications. This work suggests that the component-fusion-based topology designer is a novel approach to tailor 2D materials with expected structures and interesting properties.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Z.L. acknowledges supports from Singapore National Research Foundation–Competitive Research Program NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007. This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052

MoO₃-MoS₂ vertical heterostructures synthesized via one-step CVD process for optoelectronics

The 2D transitional metal oxides/transition-metal dichalcogenides vertical heterostructures of MoO3–MoS2 are successfully synthesized on SiO2/Si substrates via one-step chemical vapor deposition process. The vertical MoO3–MoS2 heterostructures exhibit the average size of ∼20 µm and the thickness down to ∼10 nm. Moreover, the phototransistor device based on MoO3–MoS2 heterostructures presents responsivity of 5.41 × 103 A W−1, detectivity of 0.89 × 1010 Jones and external quantum efficiency of 1263.4%, respectively, under a 532 nm wavelength light. This study affords a new path to simplify process of fabricating MoO3–MoS2 vertical heterostructures for electronic and optoelectronic applications.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)This work was supported by the National Research Foundation–Competitive Research Program of Singapore NRF-CRP21-2018-0007 and CRP22- 2019-0060, MOE Tier 2 MOE2017-T2-2-136, Tier 3 MOE2018-T3-1-002, and A∗ Star QTE programme. The National Natural Science Foundation of China (Grants 61974120 and 61904148), the Key Program for International Science and Technology Cooperation Project of Shaanxi Province (Grants 2018KWZ08 and 2019KW-029), the National Key Research and Development Program of China (2019YFC1520904), the Natural Science Foundation of Shaanxi Province (Grants 2017JM5135 and 2018JM6046) and the Foundation of the Education Department of Shaanxi Province (Grans 18JK0772 and 18JK0780), the Key Research and Development Program of Shaanxi Province (2018GY-025)

Facile synthesis of oil adsorbent carbon microtubes by pyrolysis of plant tissues

Inspired by the nature of plant tissue, carbon nanomaterials such as nanofibers have been synthesized by pyrolysis of plant tissues. However, it is challenging in synthesis of tubular structure by pyrolysis because the structure is dynamical non-steady state and always collapses in carbonization process. Herein, carbon microtubes were synthesized by a simple carbonization method-based kapok. The tubular structure with the diameter ranges from 5 to 20 μm was obtained from the final carbon samples, which shows the similar structure with kapok precursors, while the weight was lost about 90%. We demonstrated that the carbon microtubes have excellent performance in oil adsorption with the adsorption capacity of ~ 190 g g−1, which is 1.5 times larger than that of raw kapok. We found that it is reusable for more than ten times in oil adsorption application, and the adsorption capacities of carbon microtubes significantly enhanced when the temperature increased in carbonization.Ministry of Education (MOE)National Research Foundation (NRF)Accepted versionThis work is supported by the National Natural Science Foundation of China (61804125), the Key Program for International Science and Technology Cooperation Projects of Shaanxi Province (2018KWZ-08), the Foundation of the Education Department of Shaanxi Province (18JK0772 and 18JK0780), the Northwest University Doctorate Dissertation of Excellence Funds (YYB17020), the Singapore National Research Foundation under NRF Award (No. NRF-RF2013-08) and MOE under AcRF Tier 2 (MOE2016-T2-1-131)