Dopant-Induced Giant Photoluminescence of Monolayer MoS2 by Chemical Vapor Transport
Substitutional doping of 2D transition metal dichalcogenides (TMDCs) has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications. However, controllable doping of TMDCs remains a challenging issue due to the natural doping of these materials. Here, the controllable growth of Ti-doped MoS2 monolayers is demonstrated via the chemical vapor transport method, and the atomic embedded structure is confirmed by scanning transmission electron microscope with a probe corrector measurements. Furthermore, the grown Ti-doped MoS2 monolayer exhibits giant photoluminescence (PL), 85-fold stronger than a pristine MoS2 monolayer prepared by the same method. The giant PL enhancement is attributed to dopant-induced O-Ti-S units and improved interaction between the monolayer and the mica substrate, increasing the photoluminescence quantum yield and facilitating radiation recombination. The successful growth of Ti-doped MoS2 monolayer and the improvement of its optical and electrical properties by Ti doping may provide a promising method to engineer the optoelectronic properties of 2D TMDCs materials.
Volume 4, Issue 9 September 2022
Flexible and highly-sensitive pressure sensor based on controllably oxidized MXene
Conductive Ti3C2Tx MXenes have been widely investigated for the construction of flexible and highly-sensitive pressure sensors. Although the inevitable oxidation of solution-processed MXene has been recognized, the effect of the irreversible oxidation of MXene on its electrical conductivity and sensing properties is yet to be understood. Herein, we construct a highly-sensitive and degradable piezoresistive pressure sensor by coating Ti3C2Tx MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping-drying method. In situ oxidation can tune the intrinsic resistance and expand the interlayer distance of MXene nanosheets. The partially oxidized MXene-based piezoresistive pressure sensor exhibits a high sensitivity of 28.43 kPa−1, which is greater than those of pristine MXene, over-oxidized MXene, and state-of-the-art paper-based pressure sensors. Additionally, these sensors exhibit a short response time of 98.3 ms, good durability over 5000 measurement cycles, and a low force detection limit of 0.8 Pa. Moreover, MXene-based sensing elements are easily degraded and environmentally friendly. The MXene-based pressure sensor shows promise for practical applications in tracking body movements, sports coaching, remote health monitoring, and human–computer interactions.
Volume7, Issue8 August 26, 2022
Controllable and Gradient Wettability of Bilayer Two-Dimensional Materials Regulated by Interlayer Distance
Surfaces with controllable and gradient wettability often require an elaborate design of the microstructure or its response under electrical, thermal, optical, pH, and other stimuli. Generally, the wettability change under these physical or chemical effects relies on a complex mechanism that is difficult to be quantitatively described. In this study, an online controlling strategy for surface wettability and the corresponding theoretical model are put forward based on a bilayer graphene-like atomic structure. Molecular dynamics results indicate that the surface wettability varies toward hydrophilicity after sticking a bottom material regardless of its wettability. But such an influence becomes weak with increasing interlayer distance, and the overall wettability approaches that of the upper layer material gradually. This variation is elucidated by the increase of the work of adhesion, providing new insight into the wetting transparency of graphene. A theoretical model of the governing relationship is established based on the work of adhesion, which correlates the overall surface wettability with the interlayer distance and the wettabilities of individual materials. Moreover, a surface with a uniform wettability gradient is achieved by inclining the bottom material. The spontaneous and steady motion of droplets can be induced by this gradient wettability. The relevant speedup behavior is evaluated through a theoretical model considering the varying interlayer distance, which reveals the critical role of the lower layer. This study proposes a novel strategy for controllable wetting and relevant gradient surfaces using prevailing two-dimensional materials, paving new routes to many applications such as microfluidic chips, virus diagnosis, and intelligent sensors.
Volume 4, Issue 8 August 1, 2022
In Honor of Professor Daoben Zhu on the Occasion of His 80th Birthday
Protocatechuic acid (PCA) is a natural phenolic acid present in daily vegetables and fruits. Notably, PCA was demonstrated to inhibit the biological function of SerpinB9 (Sb9) and exhibit an excellent antitumor effect, showing great potential in cancer treatment. However, the short half-life time limits PCA’s wide application against cancers. To overcome this shortage of PCA, we integrated PCA and another natural product with strong self-assembling properties, isoguanosine (isoG), to develop a novel multifunctional supramolecular hydrogel with good biocompatibility and injectability, which remarkably lengthens the releasing time of PCA and exerts considerable anticancer effects in vitro and in vivo. Besides, we surprisingly found that PCA could not only target Sb9 but also restrain cancer development through activating the JNK/P38 pathway, decreasing the ROS level, and repairing cancer stemness. In all, our results demonstrate that this PCA-based hydrogel could act as a multifunctional hydrogel system equipped with considerable anticancer effects, providing potential local administration integrating with targeted therapy and chemotherapy in one simple modality.
Published as part of “Organic Functional Materials: Special Issue in Honor of Professor Daoben Zhu on His 80th Birthday”.
This special issue of ACS Materials Letters is dedicated to Professor Daoben Zhu on the occasion of his 80th birthday.
Professor Zhu was born in Shanghai in 1942. He studied at the East China University of Science and Technology from 1960 to 1965 as an undergraduate student and from 1965 to 1968 as a graduate student. He, then, joined the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) in 1968 and was promoted to a full professor in 1987. Professor Zhu was a visiting scholar (1977–1979) and a visiting scientist (1985–1986) at the Max-Planck Institute for Medical Research in Heidelberg, Germany. He was the director of ICCAS from 1992 to 2000, and the vice president of the National Natural Science Foundation of China (NSFC) from 2000 to 2007. He was also the president of the Chinese Chemical Society (1995–1998) and vice president of the Chinese Materials Society (1999–2007).
Prof. Zhu is a leading international expert in the cross-disciplinary field of molecular materials and devices. Starting with his pioneering, fundamental studies on organic conductors and superconductors in the 1980s and early studies on fullerenes, including the chemical synthesis of new fullerene derivatives and exploration of their unique physical properties, he has made many ground-breaking contributions to a broad range of different research challenges in this field. He and his group proposed new molecular design strategies for high performance organic semiconductors, and successfully developed novel p-, n-, and ambipolar organic semiconductors, as well as conjugated metal organic framework (MOFs) with high charge carrier mobilities. He made pioneering contributions to advancing the performance and understanding the structure–property relationships of organic thermoelectric materials. Another example is the invention of new device structures and techniques to successfully fabricate all-solution-processed flexible integrated circuits, organic thermoelectric converters, and novel organic pressure sensors, by using the high-performance organic semiconductors developed in his group.
Prof. Zhu has published more than 1000 papers in peer-reviewed scientific journals. He has been selected by Thomson Reuters as one of the world’s most influential scientific minds from 2014 to 2021. Because of his remarkable scientific achievements, Prof. Zhu has won the second-class prizes of the National Natural Sciences of China five times (1988, 2002, 2004, 2007, and 2014). In 2012, he won the Tan Kah Kee Science Award in Chemistry. He also received the Outstanding Achievement Award in Science and Technology from the Chinese Academy of Sciences in 2018. He was awarded the China Petroleum and Chemical Corporation Chemical Contribution Award in 2008 and the Academy Honorary Award in 2021 by the Chinese Chemical Society.
Prof. Zhu was elected as an Academician of the Chinese Academy of Sciences in 1997 and Member of the World Academy of Sciences for the advancement of science in developing countries in 2009, respectively. He is also a Fellow of the Royal Society of Chemistry and the Asia-Pacific Academy of Materials and an honorary member of the Korean Chemical Society.
This special issue contains 4 Perspectives and 23 Letters (Please check the numbers of the Perspectives and Letters in the special issue). The topics cover cutting-edge research on molecular materials and devices, including (i) molecular design, synthesis and formation of controllable assemblies of new conjugated molecules and polymers, as well as hybrid organic–inorganic functional materials, and the characterization of their structure–property relationships, (ii) preparation and physical characterization of two-dimensional conjugated MOFs, covalent organic frameworks (COFs), and graphene, and (iii) investigations of the physical properties of molecular materials at different scales as relevant for a broad range of optoelectronic devices, including OLEDs, OFET-based sensors, photodetectors, organic spin valves, thermoelectrics, and electrochromics. This special issue not only showcases the recent advances in molecular materials and devices but also provides new views and perspectives of this exciting interdisciplinary area to the readers.
We would like to express our sincere thanks to our authors for generous contribution of their recent research findings to this special issue. We also appreciate the strong support from the reviewers. Special thanks go to Dr. Carlos Toro (senior managing editor) and the editorial staff who helped edit this special issue.
Finally, we would like to send our best wishes and sincere congratulations to Prof. Daoben Zhu for his 80th birthday and his remarkable scientific achievements.
Happy birthday, Prof. Daoben Zhu!
Issue 35 September21 2022
Self-assembly of carbon nanodots induced by liquid–liquid phase separation in a surface microdroplet
Evaporating a sessile drop of ternary solutions containing one hydrotrope (such as ethanol) and two immiscible fluids exhibiting fascinating phase separation behaviours, has opened up a new pathway for controlled nanomaterial assembly. In this work, we studied the influence of liquid–liquid phase separation (LLPS) on the assembly of carbon nanodots (C-dots), 2 nm fluorescent carbon-based nanomaterials with high water solubility. Through self-evaporation of a micro-sized droplet containing ethanol, C-dot-water solution and different oils on a hydrophobic surface, C-dots rearranged into film, porous and granular structures by controlling the properties of oil component in the tenary droplet. Vapour pressure, solubility, surface tension and compositions of the oil components were investigated systematically for their impacts on the evaporation process of C-dot-laden droplets. By using confocal microscopy, we clearly revealed that C-dot assembly was triggered by LLPS in these four oil–water–ethanol ternary systems. The corresponding evaporation and assembly processes were unravelled to be determined by how the ternary solutions pass through the liquid–liquid equilibrium curves in the phase diagrams during evaporation. Our findings deepen the understanding of phase-separation behaviours for nanomaterial assembly as well as provide a novel, simple, and well-controlled approach for depositing different C-dot based nanostructures onto surfaces, which will benefit a wide range of practical applications in the fields of energy, environment and health.
Issue 1 07 September 2022
Toward cleaner production of nanocellulose: a review and evaluation
Nanocellulose has become a hotspot in the field of green and sustainable materials. As a “clean material”, however, the traditional production process is not completely clean as imagined. In recent years, considerable research progress has been made in the selection of sustainable source materials and the development of clean production processes for nanocellulose. Firstly, this review summarises research publications about sustainable nanocellulose source materials. After that, advances in cleaner nanocellulose production processes are reviewed, including improvements or replacements of chemical treatment to decrease the usage of deleterious chemicals, strengthening of mechanical methods to decrease energy input, and improvements of the overall process flow, emphasizing recycling and regeneration. Subsequently, the evaluation of the nanocellulose environment, health and safety aspects and life cycle assessments are emphasized. Ultimately, the suggestions for promoting the industrialisation of nanocellulose were proposed to provide references for the clean and large-scale production of the nanocellulose industry.
Volume42, Issue3 March，2022
Simulation study of laminar fracture recompaction of metal materials
After the shock wave is unloaded on the free surface, the laminar cracking phenomenon often occurs inside the metal. If the inner crack area of the metal is subjected to impact loading again, the metal in the tensile sparse state will gradually be compacted into a dense medium again until the laminar crack area disappears and the re-compaction process is completed. Due to the complexity of the initial tensile state of the metal laminar fracture region and the uncertainty of the state of the material after recompaction, it is difficult to verify the reliability of the macroscopic simulation problem under complex loading conditions. At present, in the case that experimental diagnosis is difficult to accurately give the initial state and recompaction state of the metal laminar fracture region entering the recompaction process, the direct numerical simulation with the ability to describe the internal details of the laminar fracture area has become an effective means to verify the reliability of macroscopic simulation. Firstly, in the direct numerical simulation modeling, the initial tensile state of the metal layer crack region is modeled as three types of cases: only laminar lobe, only holes, and both holes and laminar cracks. Then, through the direct numerical simulation of different porosity, recompaction rate, number of layer fractures and number of holes, the recompaction state of the metal layer crack area under the corresponding working conditions was obtained. Finally, under the condition that the direct simulation and macroscopic simulation are well comparable, the laminar fracture recompaction process is macroscopic modeling and simulation analysis. The analysis shows that under the condition that the macroscopic grid fracture post-processing algorithm uses full stress zeroing and temperature invariance, the macroscopic simulation can better simulate the metal laminar fracture recompaction process and recompaction state under the condition of azifer fracture in the sparse area. If the recompaction process enters the metal laminar cracking region in the initial state of containing only holes, the macroscopic simulation cannot better simulate the laminar cracking recompaction process and the recompaction state regardless of whether the hole collapse forms an interface jet.
Issue 70,11 September 2022
Direct growth of h-BN multilayers with controlled thickness on non-crystalline dielectric substrates without metal catalysts
We report an rGO-assisted CVD approach that enables the direct growth of high-quality single crystalline h-BN films with adjustable thickness and layered order on amorphous quartz and SiO2/Si substrates at relatively low temperatures. This work demonstrates a viable prototype for growing continuous ultrathin h-BN films on desired substrates without the requirement of lattice orientation, thus offering a great opportunity for their appealing applications.