Broadband lens and graphene/silicon photodiode for wide spectral imaging.

We designed a broadband lens along with a graphene/silicon photodiode for wide spectral imaging ranging from ultraviolet to near-infrared wavelengths. By using five spherical glass lenses, the broadband lens, with the modulation transfer function of 0.38 at 100 lp/mm, corrects aberrations ranging from 340 to 1700 nm. Our design also includes a broadband graphene/silicon Schottky photodiode with the highest responsivity of 0.63 A/W ranging from ultraviolet to near-infrared. By using the proposed broadband lens and the broadband graphene/silicon photodiode, several single-pixel imaging designs in ultraviolet, visible, and near-infrared wavelengths are demonstrated. Experimental results show the advantages of integrating the lens with the photodiode and the potential to realize broadband imaging with a single set of lens and a detector.

Highly Thermally Conductive and Structurally Ultra-Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management.

Highly thermally conductive graphitic film (GF) materials have become a competitive solution for the thermal management of high-power electronic devices. However, their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety. Here, we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks (LNS), which reveals a bubbling process characterized by "permeation-diffusion-deformation" phenomenon. To overcome this long-standing structural weakness, a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film (GF@Cu) with seamless heterointerface. This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K. Moreover, GF@Cu maintains high thermal conductivity up to 1088 W m-1 K-1 with degradation of less than 5% even after 150 LNS cycles, superior to that of pure GF (50% degradation). Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

Sub-second ultrafast yet programmable wet-chemical synthesis.

Wet-chemical synthesis via heating bulk solution is powerful to obtain nanomaterials. However, it still suffers from limited reaction rate, controllability, and massive consumption of energy/reactants, particularly for the synthesis on specific substrates. Herein, we present an innovative wet-interfacial Joule heating (WIJH) approach to synthesize various nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. In the WIJH, Joule heat generated by the graphene film (GF) is confined at the substrate-solution interface. Accompanied by instantaneous evaporation of the solvent, the temperature is steeply improved and the precursors are concentrated, thereby synergistically accelerating and controlling the nucleation and growth of nanomaterials on the substrate. WIJH leads to a record high crystallization rate of HKUST-1 (~1.97 µm s-1), an ultralow energy cost (9.55 × 10-6 kWh cm-2) and low precursor concentrations, which are up to 5 orders of magnitude faster, -6 and -2 orders of magnitude lower than traditional methods, respectively. Moreover, WIJH could handily customize the products' amount, size, and morphology via programming the electrified procedures. The as-prepared HKUST-1/GF enables the Joule-heating-controllable and low-energy-required capture and liberation towards CO2. This study opens up a new methodology towards the superefficient synthesis of nanomaterials and solvent-involved Joule heating.

Initialization of Nanowire or Cluster Growth Critically Controlled by the Effective V/III Ratio at the Early Nucleation Stage.

For self-catalyzed nanowires (NWs), reports on how the catalytic droplet initiates successful NW growth are still lacking, making it difficult to control the yield and often accompanying a high density of clusters. Here, we have performed a systematic study on this issue, which reveals that the effective V/III ratio at the initial growth stage is a critical factor that governs the NW growth yield. To initiate NW growth, the ratio should be high enough to allow the nucleation to extend to the entire contact area between the droplet and substrate, which can elevate the droplet off of the substrate, but it should not be too high in order to keep the droplet. This study also reveals that the cluster growth between NWs is also initiated from large droplets. This study provides a new angle from the growth condition to explain the cluster formation mechanism, which can guide high-yield NW growth.

Plasmonic Terahertz Devices and Sensors Based on Carbon Electronics.

Tunable terahertz (THz) photonic devices are imperative in a wide range of applications ranging from THz signal modulation to molecular sensing. One of the currently prevailing methods is based on arrays of metallic or dielectric resonators integrated with functional materials in response to an external stimulus, in which for the purpose of sensing the external stimuli may introduce inadvertent undesirable effects into the target samples to be measured. Here we developed an alternative approach by postprocessing nanothickness macro-assembled graphene (nMAG) films with widely tunable THz conductivity, enabling versatile solid-state THz devices and sensors, showing multifunctional nMAG-based applications. The THz conductivities of free-standing nMAGs showed a broad range from 1.2 × 103 S/m in reduced graphene oxide before annealing to 4.0 × 106 S/m in a nMAG film annealed at 2800 °C. We fabricated nMAG/dielectric/metal and nMAG/dielectric/nMAG THz Salisbury absorbers with broad reflectance ranging from 0% to 80%. The highly conductive nMAG films enabled THz metasurfaces for sensing applications. Taking advantage of the resonant field enhancement arising from the plasmonic metasurface structures and the strong interactions between analyte molecules and nMAG films, we successfully detected diphenylamine with a limit of detection of 4.2 pg. Those wafer-scale nMAG films present promising potential in high-performance THz electronics, photonics, and sensors.

Blood-Coagulation-Inspired Dynamic Bridging Strategy for the Fabrication of Multiscale-Assembled Hierarchical Porous Material.

Porous materials, from macroscopic bulk materials (MBs) with (sub-)millimeter-scale pores to tiny particles (TPs) with (sub-)nanometer-scale pores, have attracted ever-growing interest in various fields. However, the integration of multi-scale pores in one composite is promising but challenging, owing to the considerable gap in the scale of the pores. Inspired by blood coagulation, a fibrin-based dynamic bridging strategy is developed to fabricate a multiscale-assembled hierarchical porous material (MHPM), in which fibrin formed as the sub-framework for the weaving-narrow of MBs and the enwinding-load of TPs. The bio-polymerization nature makes the fabrication rapid, facile, and universal for the customizable integration of seven kinds of TPs and four kinds of MBs. Besides, the integration is controllable with high load capacity of TPs and is stable against external shock forces. The unique multi-level structure endows the MHPM with large and accessible surface area, and efficient mass transfer pathways, synergistically leading to high adsorption capacity and rapid kinetics in multiple adsorption models. This work suggests a strategy for the rational multi-level design and fabrication of hierarchical porous architectures.

Ultrathin metal-organic framework nanosheets as building blocks of lamellar nanofilms for ultrafast molecular sieving.

Metal-organic framework (MOF) nanosheets have significant potential applications including separation, catalysis, and sensors. However, the on-demand design with tunable thickness and morphology remains a great challenge, leading to difficulties in modulating their hierarchical assembly for the preparation of macroscopic films. Herein, we report the successful synthesis of smooth and ultrathin MOF (Cu-TCPP (TCPP = 4,4,4,4-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid))) nanosheets used in lamellar nanofilms for the rejection of organic molecules from water. Dopamine hydrochloride (DA-HCl) is used as an adjuvant in the synthesis. Facilitated by a HCl acid environment and DA competitive coordination, the normal and lateral growths of Cu-TCPP nanosheets are modulated to achieve the desired thickness and morphology. DA-HCl can be also easily removed from the nanosheets without affecting their physicochemical properties. The as-synthesized nanosheets are utilized as nanofilm building blocks in which they are stacked into ordered bricks. The obtained membrane displays an ultrahigh water permeance of 2540 L m-2 h-1 bar-1, which is two orders of magnitude higher than the currently reported polymer membranes, while it does not sacrifice the solute rejection as completely determined by the intrinsic pore size of the nanosheets (i.e., 98.8% for molecules larger than 1.3 nm). This work provides a novel and facile strategy to tailor the morphology of the MOF nanosheets for maximizing their functionalities and structure superiority in many engineering applications.

A comprehensive review on reactive oxygen species (ROS) in advanced oxidation processes (AOPs).

In this account, the reactive oxygen species (ROS) were comprehensively reviewed, which were based on electro-Fenton and photo-Fenton processes and correlative membrane filtration technology. Specifically, this review focuses on the fundamental principles and applications of advanced oxidation processes (AOPs) based on a series of nanomaterials, and we compare the pros and cons of each method and point out the perspective. Further, the emerging reviews regarding AOPs rarely emphasize the involved ROS and consider the convenience of radical classification and transformation mechanism, such a review is of paramount importance to be needed. Owing to the strong oxidation ability of radical (e.g., •OH, O2•-, and SO4•-) and non-radical (e.g., 1O2 and H2O2), these ROS would attack the organic contaminants of emerging concern, thus achieving the goal of environmental remediation. Hopefully, this review can offer detailed theoretical guidance for the researchers, and we believe it able to offer the frontier knowledge of AOPs for wastewater treatment plants (WWTPs).

2D-Topology-Seeded Graphitization for Highly Thermally Conductive Carbon Fibers.

Highly thermally conductive carbon fibers (CFs) have become an important material to meet the increasing demand for efficient heat dissipation. To date, high thermal conductivity has been only achieved in specific pitch-based CFs with high crystallinity. However, obtaining high graphitic crystallinity and high thermal conductivity beyond pitch-CFs remains a grand challenge. Here, a 2D-topology-seeded graphitization method is presented to mediate the topological incompatibility in graphitization by seeding 2D graphene oxide (GO) sheets into the polyacrylonitrile (PAN) precursor. Strong mechanical strength and high thermal conductivity up to 850 W m- 1 K-1 are simultaneously realized, which are one order of magnitude higher in conductivity than commercial PAN-based CFs. The self-oxidation and seeded graphitization effect generate large crystallite size and high orientation to far exceed those of conventional CFs. Topologically seeded graphitization, verified in experiments and simulations, allows conversion of the non-graphitizable into graphitizable materials by incorporating 2D seeds. This method extends the preparation of highly thermally conductive CFs, which has great potential for lightweight thermal-management materials.

Multifunctional Macroassembled Graphene Nanofilms with High Crystallinity.

A "cooling-contraction" method to separate large-area (up to 4.2 cm in lateral size) graphene oxide (GO)-assembled films (of nanoscale thickness) from substrates is reported. Heat treatment at 3000 °C of such free-standing macroscale films yields highly crystalline "macroassembled graphene nanofilms" (nMAGs) with 16-48 nm thickness. These nMAGs present tensile strength of 5.5-11.3 GPa (with ≈3 µm gauge length), electrical conductivity of 1.8-2.1 MS m-1 , thermal conductivity of 2027-2820 W m-1 K-1 , and carrier relaxation time up to ≈23 ps. As a demonstration application, an nMAG-based sound-generator shows a 30 µs response and sound pressure level of 89 dB at 1 W cm-2 . A THz metasurface fabricated from nMAG has a light response of 8.2% for 0.159 W mm-2 and can detect down to 0.01 ppm of glucose. The approach provides a straightforward way to form highly crystallized graphene nanofilms from low-cost GO sheets.

A polyimide-pyrolyzed carbon waste approach for the scalable and controlled electrochemical preparation of size-tunable graphene.

Carbon materials are widely used in numerous fields, thus changing our lives. With the increasing consumption of carbon-based products, the disposal of consequent wastes has become a challenge due to their inert nature, which is hard to degrade, burn, or melt. Here, a recyclable strategy is proposed to deal with the explosive growth of carbon wastes. Through a fast and clean electrochemical method, carbon wastes are converted into functional building blocks of high value, such as graphene and graphene quantum dots (GQDs). For typical polyimide-pyrolyzed carbon (PPC), we establish the relationship between the chemical structure of raw materials and the characteristics of graphene products, including size and yield. The size-tunable graphene ranging from 3 nm to tens of micrometers is prepared by tuning the sp3/sp2 carbon ratio of PPC from 0.5 to 0 at adjustable temperatures (800 °C-2800 °C). Significantly, PPC with a bicontinuous structure (comprising sp2 and sp3) was efficiently cut into GQDs in 2 h with a high yield of 98%. Our protocol offers great potential for the scale-up preparations and applications of GQDs. Besides, we demonstrate that the GQDs performed well as dispersants to disperse hydrophobic carbon nanotubes (0.6 mg mL-1) in water and improved the gravimetric capacitance of graphene-based supercapacitors by 79.4% with 3% GQDs added as nano-fillers.

Heavy Water Enables High-Voltage Aqueous Electrochemistry via the Deuterium Isotope Effect.

Aqueous electrolytes, which possess the advantages of nonflammability and high ionic conductivity for safe and sustainable energy storage systems, are restricted by their narrow potential windows due to water electrolysis. The recent study of high-voltage aqueous electrolytes has mainly focused on the molecular-level hydration structure of electrolyte salts, while the influence from subatomic-scale neutrons of the water solvent has never been considered. Here, for the first time, we report an electrochemical isotope effect in which the numerically increased neutrons in the water solvent extend the potential window of aqueous electrolytes. This effect is caused by the following factors: the lower zero-point energy of the deuterium compound, the smaller ion product, and the larger dehydration energy of heavy water. It is affected by ion species, electrolyte concentrations, and the ratio of deuterium to protium. Our finding provides the new insight into aqueous electrochemistry that the isotope in molecular water improves the performance of aqueous electrolytes.

Hierarchical Porous SWCNT Stringed Carbon Polyhedrons and PSS Threaded MOF Bilayer Membrane for Efficient Solar Vapor Generation.

Interfacial solar vapor generation is considered to be an efficient and eco-friendly technology for harvesting solar energy and providing freshwater. However, the efficient and long-term steady evaporation of seawater under 1 sun becomes a critical issue when it comes to practical applications. Based on this issue, a special double-layer structure, which contains a metal-organic-framework-derived hierarchical porous carbon membrane (HPCM) for solar absorption and a polystyrene sulfonate (PSS)@Cu3 (BTC)3 •3H2 O (HKUST-1)/single-walled carbon nanotube (SWCNT) (PHS) membrane for water supply and salt blocking, is designed in this work. The converted heat is utilized efficiently in situ to drive the evaporation of water-trapped HPCM. The PHS membrane with PSS modified channels successfully prevents the deposition of salt. Due to the synergistic combination of the HPCM and PHS membranes, the device exhibits a remarkably high water evaporation rate of 1.38 kg m-2 h-1 and solar-vapor generation efficiency of 90.8% under 1 sun.

Reduced {001}-TiO2-x photocatalysts: noble-metal-free CO2 photoreduction for selective CH4 evolution.

The preparation of reduced TiO2 photocatalysts with high Ti3+ concentration is a great challenge due to their instability in air. Here we report a new approach for the synthesis of reduced TiO2 with {001} facets exposed via a hydrothermal process. By the introduction of fluoride atoms, {001} and {101} facets are formed, which act as hole and electron collectors, respectively, for charge separation. By adjusting the volume of HF added, a rutile-anatase transition is observed for the first time. EPR spectra confirm the generation of Ti3+ species in the bulk of TiO2, and Ti3+ signals are studied in the anatase and rutile phases separately. The quantified EPR shows that reduced TiO2 samples present 14 000-fold more spins compared to the pristine TiO2, and the intensity can reach as high as 24.6 × 1019 spins per g. The obtained samples also have a unique disordered layer with a thickness of 1-2 nm on their surfaces, which contributes to the stabilization of the formed Ti3+ species by preventing their oxidation in air. In addition, the synthesized reduced TiO2 samples also exhibit wide-spectrum solar light absorption, especially in the near-infrared region. Owing to their enhanced solar light absorption, improved electron-hole separation and special facet exposure, these samples exhibit enhanced photocatalytic CO2 reduction performance and high CH4 selectivity under solar light irradiation, in the absence of a noble metal Pt as a co-catalyst.

Increased expression of phospho-acetyl-CoA carboxylase protein is an independent prognostic factor for human gastric cancer without lymph node metastasis.

Upregulation of acetyl-CoA carboxylase (ACC), as a rate-limiting enzyme of fatty acid synthesis,has been recognized in multiple human cancers, implicating a critical role in cancer development and progression; yet, its role in gastric cancer still remains unclear. In the present study, we detected ACC and phosphorylated form of ACC (pACC) expression in gastric cancers and explored its clinical significance. Tissue microarray blocks containing primary gastric cancer and adjacent normal mucosa specimens obtained from 1,072 Chinese patients were used for the detection of ACC and pACC expression by immunohistochemistry. Gastric cancer cell lines were treated by metformin, and pACC was measured by Western blotting. ACC overexpression was observed in all the tumor specimens. High expression of pACC was found in 630 (58.8 %) of the 1,072 primary tumors and in 237 (66.6 %) of the 356 primary tumors without lymph node metastasis. Absent/low expression of pACC significantly correlated with advanced T stage (P < 0.001), tumor size (P = 0.010), lymph node metastasis (P < 0.001), advanced disease stage (P < 0.001), and poor histological differentiation (P = 0.014) in 1,072 primary tumors, and with advanced T stage (P = 0.015), tumor size (P = 0.017), and poor histological differentiation (P = 0.001) in 356 tumors without lymph node metastasis. Kaplan-Meier analysis showed that high expression of pACC is strongly related to better survival rates in all gastric cancer patients (P = 0.006). Cox regression analysis revealed that pACC is an independent prognostic factor only in patients without lymph node metastasis (P = 0.016). Metformin treatment leaded to increased expression of pACC, which, in turn, resulted in the reduction of cell proliferation and colony formation of gastric cancer cells (P < 0.05). Increased activation of ACC is frequent in human gastric cancer, and downregulation of pACC is an important prognostic factor, suggesting that ACC/pACC might be a potential target for cancer intervention.

Highly-dispersed boron-doped graphene nanoribbons with enhanced conductibility and photocatalysis.

Highly-dispersed boron-doped graphene nanoribbons (B-GNRs), prepared by a simple vacuum activation method, exhibit p-type semiconductor properties and provide many more zigzag- and armchair-edges to facilitate control of the bandgap. B-GNRs are used for the photodegradation of Rhodamine B in order to demonstrate their excellent conductivity and photocatalytic activity.