Insight into Facile Ion Diffusion in Resistive Switching Medium toward Low Operating Voltage Memory.

The rapid increase in data storage worldwide demands a substantial amount of energy consumption annually. Studies looking at low power consumption accompanied by high-performance memory are essential for next-generation memory. Here, Graphdiyne oxide (GDYO), characterized by facile resistive switching behavior, is systematically reported toward a low switching voltage memristor. The intrinsic large, homogeneous pore-size structure in GDYO facilitates ion diffusion processes, effectively suppressing the operating voltage. The theoretical approach highlights the remarkably low diffusion energy of the Ag ion (0.11 eV) and oxygen functional group (0.6 eV) within three layers of GDYO. The Ag/GDYO/Au memristor exhibits an ultralow operating voltage of 0.25 V with a GDYO thickness of 5 nm; meanwhile, the thicker GDYO of 29 nm presents multilevel memory with an ON/OFF ratio of up to 104. The findings shed light on memory resistive switching behavior, facilitating future improvements in GDYO-based devices toward opto-memristors, artificial synapses, and neuromorphic applications.

Controlled Growth Lateral/Vertical Heterostructure Interface for Lithium Storage.

Artificial heterostructures with structural advancements and customizable electronic interfaces are fundamental for achieving high-performance lithium-ion batteries (LIBs). Here, a design idea for a covalently bonded lateral/vertical black phosphorus (BP)-graphdiyne oxide (GDYO) heterostructure achieved through a facile ball-milling approach, is designed. Lateral heterogeneity is realized by the sp2-hybridized mode P-C bonds, which connect the phosphorus atoms at the edges of BP with the carbon atoms of the terminal acetylene in GDYO. The vertical connection of the heterojunction of BP and GDYO is connected by P-O-C bond. Experimental and theoretical studies demonstrate that BP-GDYO incorporates interfacial and structural engineering features, including built-in electric fields, chemical bond interactions, and maximized nanospace confinement effects. Therefore, BP-GDYO exhibits improved electrochemical kinetics and enhanced structural stability. Moreover, through ex- and in-situ studies, the lithiation mechanism of BP-GDYO, highlighting that the introduction of GDYO inhibits the shuttle/dissolution effect of phosphorus intermediates, hinders volume expansion, provides more reactive sites, and ultimately promotes reversible lithium storage, is clarified. The BP-GDYO anode exhibits lithium storage performance with high-rate capacity and long-cycle stability (602.6 mAh g-1 after 1 000 cycles at 2.0 A g-1). The proposed interfacial and structural engineering is universal and represents a conceptual advance in building high-performance LIBs electrode.

A novel functionalized graphdiyne oxide membrane for efficient removal and rapid detection of mercury in water.

In practice, efficient, rapid and simple removal of Hg(II) from water using nano adsorbents remains an extreme challenge at present. In this work, a novel Hg(II) adsorbent based on functionalized graphdiyne oxide (GDYO-3M) membrane was designed for the purpose of effective and prompt removal of Hg(II) from environmental water for the first time. Through filtration, the proposed GDYO-3M membrane (4 cm diameter size) fulfilled an exceeding 97% removal efficiency in > 10 L water containing 0.1 mg/L Hg(II) within 1 h. Due to the presence of -SH groups, the GDYO-3M membrane demonstrates an excellent selectivity for Hg(II) vs. 14 co-existing metal ions. In the meantime, the GDYO-3M membrane represents a favorable reproducibility (above 95% Hg(II) removal) after 9 successive adsorption-desorption cycles. For the mechanism, it is believed that the active sites in the adsorption process mainly include -SH groups, oxygen-containing functional groups, and alkyne bonds. Further, the GDYO-3M membrane can be utilized as an enrichment approach for sensitive analysis of Hg(II) in water based on energy dispersion X-ray fluorescence spectrometry (ED-XRF), whose detection limit (LOD) reaches 0.2 µg/L within 15 min. This work not only provides a green and efficient method for removing Hg(II), but also renders an approach for rapid, sensitive and portable Hg(II) detection in water.

Graphdiyne Oxide-Mediated Photodynamic Therapy Boosts Enhancive T-Cell Immune Responses by Increasing Cellular Stiffness.

Purpose: Nanomaterial-based photodynamic therapy (PDT) has been commonly used for the treatment of cancerous tumors. Despite significant achievements made in this field, the intrinsic impact of nanomaterials-based PDT on the mechanical properties of oral squamous cell carcinoma (OSCC) cells is not entirely understood. Here, we used atomic force microscopy (AFM) to measure the stiffness of OSCC cells subjected to PDT in co-culture systems to evaluate the T cell-mediated cancer cell-killing effects. Methods: In this study, AFM was used to assess the stiffness of PDT-subjected cells. The phototoxicity of graphdiyne oxide (GDYO) was assessed using confocal laser scanning microscopy (CLSM), measurements of membrane cholesterol levels, and assessments of the F-actin cytoskeleton. A co-culture system was used to evaluate the effects of CD8+ T cells (cytotoxic T lymphocytes), demonstrating how PDT modulates the mechanical properties of cancer cells and activates T cell responses. The antitumor immunotherapeutic effect of GDYO was further evaluated in a murine xenograft model. Results: GDYO increased the mechanical stiffness of tumor cells and augmented T-cell cytotoxicity and inflammatory cytokine secretion (IFN-γ and TNF-α) under laser in vitro. Furthermore, GDYO-based PDT exerted inhibitory effects on OSCC models and elicited antitumor immune responses via specific cytotoxic T cells. Conclusion: These results highlight that GDYO is a promising candidate for OSCC therapy, shifting the mechanical forces of OSCC cells and breaking through the barriers of the immunosuppressive tumor microenvironment. Our study provides a novel perspective on nanomaterial-based antitumor therapies.

Graphdiyne oxide elicits a minor foreign-body response and generates quantum dots due to fast degradation.

Graphdiyne (GDY) is a novel two-dimensional (2D) carbon allotrope that has attracted much attention in materials, physics, chemistry, and microelectronics for its excellent properties. Much effort has been devoted to exploring the biomedical applications of GDY in 2D carbon nanomaterials, especially for smart drugs and gene delivery. However, few studies have focused on the biocompatibility and potential environmental hazards of GDY and its derivatives. In this study, graphdiyne oxide (GDYO) and graphene oxide (GO) were obtained using different oxidation methods. Their cytotoxicity and hemolysis in vitro and biocompatibility in subcutaneous and peritoneal locations in vivo were compared. GDYO had very low biotoxicity in vitro and was moderately biocompatible in the muscle and abdominal cavity in vivo. Highly oxidized products and graphdiyne quantum dots (GDQDs) were observed in peritoneal cells. GDYO had better biocompatibility and its sheet size was easily diminished through oxidative degradation. Therefore, GDYO is a good candidate for use in 2D carbon nanomaterials in biomedicine.

Giant Water Uptake Enabled Ultrahigh Proton Conductivity of Graphdiyne Oxide.

Proton conductors have attracted great attention in various fields, especially in energy production. Here, we find that graphdiyne oxide (GDYO), derived from graphdiyne (GDY), features the highest proton conductivity of 0.54 S cm-1 (100 % RH, 348 K) among the oxidized carbon allotropes reported so far. The sp- and sp2 -co-hybridized carbon skeleton of GDY enables GDYO with the giant water uptake, which is 2.4 times larger than that of graphene oxide (GO), resulting in ultrahigh proton conductivity by increasing the proton concentration and proton conduction pathways. This ultrahigh proton conductivity of GDYO is further proved in a methanol fuel cell by using GDYO membrane as proton exchange membrane. The GDYO membrane enables the cell with higher open circuit voltage, larger power density and lower methanol permeability, compared with commercial Nafion 117. Moreover, the GDYO membrane bears high ion exchange capacity, good acidic stability and low swelling ratio.

Multi-functional Nanodrug Based on a Three-dimensional Framework for Targeted Photo-chemo Synergetic Cancer Therapy.

Targeted synergistic therapy has broad prospects in tumor treatments. Here, a multi-functional nanodrug GDYO-CDDP/DOX@DSPE-PEG-MTX (GCDM) based on three traditional anticancer drugs (doxorubicin (DOX), cisplatin (CDDP) and methotrexate (MTX)) modified graphdiyne oxide (GDYO) is described, for diagnosis and targeted cancer photo-chemo synergetic therapy. In this system, for the first time, these three traditional anti-cancer drugs have played new roles and can reduce multidrug resistance through synergistic anti-tumor effects. Cisplatin can be hybridized with GDYO to form a multifunctional and well-dispersed three-dimensional framework, which can not only be used as nano-drug carriers to achieve high drug loading rates (40.3%), but also exhibit excellent photothermal conversion efficiency (47%) and good photodynamic effects under NIR irradiation. Doxorubicin (DOX) is loaded onto GDYO-CDDP through π-π stacking, which is used as an anticancer drug and as a fluorescent probe for nanodrug detection. Methotrexate (MTX) can be applied in tumor targeting and play a role in synergistic chemotherapy with DOX and CDDP. The synthesized multi-functional nanodrug GCDM has good biocompatibility, active targeting, long-term retention, sustained drug release, excellent fluorescence imaging capabilities, and remarkable photo-chemo synergistic therapeutic effects.

Antibacterial Activity of Graphdiyne and Graphdiyne Oxide.

From manufacture to disposal, the interaction of graphdiyne based nanomaterials with living organisms is inevitable and crucial. However, the cytotoxic properties of this novel carbon nanomaterial are rarely investigated, and the mechanisms behind their cytotoxicity are totally unknown. In this study, the antibacterial activity of graphdiyne (GDY) and graphdiyne oxide (GDYO) is reported. GDY is capable of inhibiting broad-spectrum bacterial growth while exerting moderate cytotoxicity on mammalian cells. In comparison, GDYO exhibits lower antibacterial activity than that of GDY. Then an alterable, synergetic antibacterial mechanism of GDY, involving wrapping bacterial membrane, membrane insertion and disruption, and reactive oxygen species generation is demonstrated, while the differential gene expression analysis indicates that GDY could only alter the bacterial metabolism slightly and the oxidative stress route may be a minor bactericidal factor. The investigation of the antibacterial behaviors of GDY based nanomaterials may provide useful guidelines for the future design and application of this novel molecular allotrope of carbon.

A Graphdiyne Oxide-Based Iron Sponge with Photothermally Enhanced Tumor-Specific Fenton Chemistry.

Fenton reaction-mediated oncotherapy is an emerging strategy which uses iron ions to catalytically convert endogenous hydrogen peroxide into hydroxyl radicals, the most reactive oxygen species found in biology, for efficient cancer therapy. However, Fenton reaction efficiency in tumor tissue is typically limited due to restrictive conditions. One strategy to overcome this obstacle is to increase the temperature specifically at the tumor site. Herein, a tumor-targeting iron sponge (TTIS) nanocomposite based on graphdiyne oxide, which has a high affinity for iron is described. TTIS can accumulate in tumor tissue by decoration with a tumor-targeting polymer to enable tumor photoacoustic and magnetic resonance imaging. With its excellent photothermal conversion efficiency (37.5%), TTIS is an efficient photothermal therapy (PTT) agent. Moreover, the heat produced in the process of PTT can accelerate the release of iron ions from TTIS and simultaneously enhance the efficiency of the Fenton reaction, thus achieving a combined PTT and Fenton reaction-mediated cancer therapy. This work introduces a graphdiyne oxide-based iron sponge that exerts an enhanced antitumor effect through PTT and Fenton chemistry.

Tumor Reoxygenation and Blood Perfusion Enhanced Photodynamic Therapy using Ultrathin Graphdiyne Oxide Nanosheets.

Both diffusion-limited and perfusion-limited hypoxia are associated with tumor progression, metastasis, and the resistance to therapeutic modalities. A strategy that can efficiently overcome both types of hypoxia to enhance the efficacy of cancer treatment has not been reported yet. Here, it is shown that by using biomimetic ultrathin graphdiyne oxide (GDYO) nanosheets, both types of hypoxia can be simultaneously addressed toward an ideal photodynamic therapy (PDT). The GDYO nanosheets, which are oxidized and exfoliated from graphdiyne (GDY), are able to efficiently catalyze water oxidation to release O2 and generate singlet oxygen (1O2) using near-infrared irradiation. Meanwhile, GDYO nanosheets also exhibit excellent light-to-heat conversion performance with a photothermal conversion efficiency of 60.8%. Thus, after the GDYO nanosheets are coated with iRGD peptide-modified red blood membrane (i-RBM) to achieve tumor targeting, the biomimetic GDYO@i-RBM nanosheets can simultaneously enhance tumor reoxygenation and blood perfusion for PDT. This study provides new insights into utilizing novel water-splitting materials to relieve both diffusion- and perfusion-limited hypoxia for the development of a novel therapeutic platform.

Comparisons between Graphene Oxide and Graphdiyne Oxide in Physicochemistry Biology and Cytotoxicity.

Graphdiyne (GDY) and graphene are regarded as two promising two-dimensional carbon-based materials, which have unique planar structure and novel electronic properties. Differences between the two carbon allotropes in their physicochemistry biology and cytotoxicity have never been explored. Here, we chemically functionalized the surface of the two carbon allotropes using similar oxidation processes and compared their physicochemistry, biology, and mutagenesis. Graphene oxide (GO) and GDY oxide (GDYO) showed similarities in their size, morphology, and physical spectral characteristics, excepting the differences in sp- and sp2-hybridizations and Fourier transform infrared spectroscopy. GDYO was well soluble in various media. In contrast, GO was only soluble in H2O, but kinetically aggregated in 0.9% NaCl, phosphate buffered saline, and cell media within 24 h incubation when its concentrations increased. GO nanoparticles adhered and aggregated to the surface of a human hepatocyte membrane, resulting in cell membrane ruffle, methuosis, and apoptosis. Adhesion of GO to cells caused cell stress and induced reactive oxygen species. In contrast, GDYO did not adhere to the cell membrane to produce the related consequences. Both GDYO and GO showed in vivo mutagenesis potential but no erythrocyte-killing effect, and both were antioxidant and bioequivalent at binding to single-stranded DNA and doxorubicin, thus causing fluorescence quenching. The present study significantly enriches our existing knowledge of GO/alkene and GDYO/alkyne chemistry.

Carbon Atom Hybridization Matters: Ultrafast Humidity Response of Graphdiyne Oxides.

Graphdiyne oxide (GDO), the oxidized form of graphdiyne (GDY), exhibits an ultrafast humidity response with an unprecedented response speed (ca. 7 ms), which is three times faster than that of graphene oxide (GO) with the same thickness and O/C ratio. The ultrafast humidity response of GDO is considered to benefit from the unique carbon hybridization of GDO, which contains acetylenic bonds that are more electron-withdrawing than ethylenic bonds in GO, consequently giving rise to a faster binding rate with water. This distinctive structure-based property enables the fabrication of a novel GDO-based humidity sensor with an ultrafast response speed and good selectivity against other kinds of gas molecules as well as high sensitivity. These properties allow the sensor to accurately monitor the respiration rate change of human and hypoxic rats.