Ultra-Fast Preparation of Large-Area Graphdiyne-Based Membranes via Alkynylated Surface-Modification for Nanofiltration

Polarity-Switchable Dual-Mode Photoelectrochemical Cancer Marker Immunoassay Based on a Metal-Organic Framework@Nitrogen-Doped Graphdiyne Heterojunction

A photocurrent polarity-switching photoelectrochemical (PEC) assay has been used for its anti-interference ability and superior accuracy compared to a conventional PEC measuring system. In this work, an ultrasensitive photocurrent polarity-switchable assay was established for sensitive prostate-specific antigen (PSA) detection based on a novel metal-organic framework (MOF) and graphdiyne@polyaniline (GDY@PANI)-sensitized structure as a photoactive material. The nitrogen-doped carbon nanolayers wrapped around graphdiyne and a zinc-based MOF were synthesized via a hydrothermal method. As an excellent photoactive material, the type II heterostructure (MOF/GDY@PANI) not only reduced the recombination of generated electron-hole pairs but also resulted in a significant increase in photoelectric conversion efficiency. Furthermore, its photocurrent was 4.6-fold higher than that of GDY@PANI and 37-fold higher than the proposed MOF. The integrated MOF/GDY@PANI/antibody (Ab) glassy carbon photoelectrode (GCE) was used as a PEC immunosensor for PSA detection (signal-off mode) and exhibited a wide linear dynamic range from 0.1 fg/mL to 10 pg/mL and a limit of detection of 0.05 fg/mL. The GCE modified with MOF and primary antibody (Ab1) (GCE/MOF/Ab1) produced a cathodic photocurrent, and in the presence of PSA, after the introduction of GDY@PANI-labeled-secondary antibody (Ab2) onto the surface of GCE/MOF/Ab1 and formation of an immunocomplex, the photocurrent amplified and switched to an anodic current. Due to high photoelectric conversion efficiency and good polarity-switching ability of GDY@PANI, the proposed immunosensor presented a turn-on photoelectrochemical performance for PSA detection at a wide linear range from 0.1 to 10 pg/mL and ultralow detection limit of 0.03 fg/mL. Compared to signal-off mode, the sensitivity increased 2-fold and the effect of interferences produces more reliable results due to photocurrent switching, and its effectiveness was evaluated against an enzyme-linked immunosorbent assay (ELISA) using spiked real human serum samples. The positive and promising outcomes achieved by the proposed immunosensor imply that the developed platform has the potential to serve as an excellent enzyme-free photoanode immunosensor for early cancer diagnosis and therapeutic monitoring.

Covalent Organic Frameworks for Membrane Separation

Membranes with switchable wettability, solvent resistance, and toughness have emerged as promising materials for separation applications. However, challenges like limited mechanical strength, poor chemical stability, and structural defects during membrane fabrication hinder their widespread adoption. Covalent organic frameworks (COFs), crystalline materials constructed from organic molecules connected by covalent bonds, offer a promising solution due to their high porosity, stability, and customizable properties. The ordered structures and customizable functionality provide COFs with a lightweight framework, large surface area, and tunable pore sizes, which have attracted increasing attention for their applications in membrane separations. Recent research has extensively explored the preparation strategies of COF membranes and their applications in various separation processes. This review uniquely delves into the influence of various COF membrane fabrication techniques, including interfacial polymerization, layer-by-layer assembly, and in situ growth, on membrane thickness and performance. It comprehensively explores the design strategies and potential applications of these methods, with a particular focus on gas separation, oil/water separation, and organic solvent nanofiltration. Furthermore, future opportunities, challenges within this field, and potential directions for future development are proposed.

Interfacial [S─Cu─C] Bonds Induced π-d Electron Coupling Toward Modulating Charge Transfer for Efficient Solar Water Oxidation

Regulating the interfacial electric field to achieve rapid charge transfer is crucial for superior photoelectrochemical water splitting. Herein, the ultra-thin hydrogen-substituted graphdiyne (HsGDY) is precisely assembled on the surface of CdS nanorod array (Cu-CdS-HsGDY) by an in situ polymerization strategy. The strong π-d electron coupling is aroused by the delocalized π electrons of HsGDY and the delocalized d electrons of CdS through the interfacial [S─Cu─C] bonds. The strong interfacial electric field can effectively promote the charge localization distribution and reduce the charge transfer resistance. The optimized Cu-CdS-HsGDY photoanode obtain a photocurrent density as high as 4.83 mA cm-2 at 1.23 V versus reversible hydrogen electrode in neutral electrolyte solution under AM 1.5G illumination, which is 6.8 times that of the pristine CdS. Moreover, the photoanode maintains an initial photocurrent density of 84% within 4 h without any assistance of sacrificial agents, which is a rather competitive performance of similar sulfide photoanodes. The mechanism of strong π-d electron coupling on interfacial charge transfer and surface reaction kinetics is investigated by transient spectroscopy measurements, density functional theory calculation, and finite element simulation analysis. This work provides new insights into designing a reasonable interface structure to regulate charge transfer for achieve efficient PEC water splitting.

The Interfacial Interpenetration Effect for Controlled Reaction Stability of Palladium Catalysts

Tailoring well-defined interfacial structures of heterogeneous metal catalysts has become an effective strategy for identifying the interface relationships and facilitating the reactions involving multiple intermediates. Here, a particle-particle heterostructure catalyst consisting of Pd and copper oxide nanoparticles is designed to achieve high-performance alkaline methanol oxidation electrocatalysis. The strong coupling particle-particle heterostructure catalyst induced a unique interfacial interpenetration effect to improve the interfacial charge redistribution and regulate the d-band structure for optimizing the adsorption of CO intermediates on the catalyst. The resulting catalyst shows impressive mass activity (4.0 A mgPd-1) and current density (215.8 mA cm-2) for the methanol oxidation reaction (MOR) in alkaline media, which is 80.0 and 154.1 times higher than 10% Pd/C. The catalyst also exhibited outstanding stability for the MOR without obvious mass activity decay after 30,000 cycles. Experimental results and theoretical simulation (DFT) studies show that the chemical bond of the Cu-O-Pd interface can be regulated by the Pd penetration effect, greatly improving the activity and stability of the MOR. The present work exhibits the superiority of the metal particle-metal oxide heterostructure interface toward the rational design of advanced electrocatalysts.

Janus structural TaON/Graphene-like carbon dual-supported Pt electrocatalyst enables efficient oxygen reduction reaction

Developing carbon-supported Pt-based electrocatalysts with high activity and long-durability for the oxygen reduction reaction (ORR) is an enormous challenge for their commercial applications due to the corrosion of carbon supports in acid/alkaline solution at high potential. In this work, a Janus structural TaON/graphene-like carbon (GLC) was synthesized via an in-situ molecular selfassembly strategy, which was used as a dual-carrier for platinum (Pt). The as-obtained Pt/TaON/GLC presents high half-wave potential (0.94 V vs. RHE), excellent mass (1.48 A mgPt-1) and specific (1.75 mA cmPt-2) activities at 0.9 V, and superior long-term durability with a minimal loss (8.0 %) of mass activity after 10,000 cycles in alkaline solution, outperforming those of Pt/C and other catalysts. The structural characterizations and density functional theory (DFT) calculations indicate that the Pt/TaON/GLC catalyst exhibits the maximum synergies, including enhanced interfacial electron density, improved charge transfer, enhanced O2 adsorption, andsuperimposed OO cleavage. This work shows a potential strategy for preparing the high-active and long-durable Pt-based electrocatalyst by synergism-promoted interface engineering.

Photocatalytically self-cleaning graphene oxide nanofiltration membranes reinforced with bismuth oxybromide for high-performance water purification

Graphene oxide (GO) membranes have emerged as promising candidates for water purification applications, owing to their unique physicochemical attributes. Nevertheless, the trade-off between permeability and selectivity, coupled with their vulnerability to membrane fouling, poses significant challenges to their widespread industrial deployment. In this study, we introduce an innovative in-situ growth and layer-by-layer assembly technique for fabricating multilayer GO membranes reinforced with bismuth oxybromide (BiOBr) on commonly employed Nylon substrates. This method allows for the creation of two-dimensional lamellar membranes capable of photocatalytic self-cleaning and tunable nanochannel dimensions. The synthesized GO/BiOBr composite membranes exhibit remarkable water permeance rates (approximately 493.9 LMH/bar) and high molecular rejection efficiency (>99 % for Victoria Blue B and Congo Red dyes). Notably, these membranes showcase an enhanced photocatalytic self-cleaning performance upon exposure to visible light. Our work provides a viable route for the fabrication of functionalized GO-based nanofiltration membranes with BiOBr inclusions, offering a synergistic combination of high water permeability, modifiable nanochannels, and effective self-cleaning capabilities through photocatalysis.

Tailoring the Electronic Structure and Properties of Graphdiyne by Cyano Groups

Two-dimensional (2D) materials, such as 2D carbon-based systems, have been recently the subject of intense studies, thanks to their optoelectronic properties and promising electronic performances. 2D carbon-based materials such as graphdiyne (GDY) represent an optimal platform for tuning the optoelectronic properties via precise chemical functionalization. Here, we report a synthetic strategy to precisely introduce cyano groups into the 2D GDY backbone in order to tune the electronic properties of GDY. Three kinds of cyano-modified GDY have been synthesized, namely, bearing one cyano group (CNGDY), two CN in meta (m-CNGDY), and two in para (p-CNGDY) positions. A variety of experimental data as well as first-principles calculations allowed us to elucidate the role of the cyano groups in tuning the structural and functional properties of GDYs. We found that an increase in the number of cyano groups reduces the interlayer spacing between GDY layers, increases the lithium adsorption amount, as well as impacts the lithium diffusion rate, while changes in meta- or para-position impact the energy band gap.

Separation of oxygen from nitrogen using a graphdiyne membrane: a quantum-mechanical study

Efficient separation of oxygen and nitrogen from air is a process of great importance for many industrial and medical applications. Two-dimensional (2D) membranes are very promising materials for separation of gases, as they offer enhanced mass transport due to their smallest atomic thickness. In this work, we examine the capacity of graphdiyne (GDY), a new 2D carbon allotrope with regular subnanometric pores, for separating oxygen (16O2) from nitrogen (14N2). A quantum-mechanical model has been applied to the calculation of the transmission probabilities and permeances of these molecules through GDY using force fields based on accurate electronic structure computations. It is found that the 16O2/14N2 selectivity (ratio of permeances) is quite high (e.g., about 106 and 102 at 100 and 300 K, respectively), indicating that GDY can be useful for separation of these species, even at room temperature. This is mainly due to the N2 transmission barrier (∼0.37 eV) which is considerably higher than the O2 one (∼0.25 eV). It is also found that molecular motions are quite confined inside the GDY pores and that, as a consequence, quantum effects (zero-point energy) are significant in the studied processes. Finally, we explore the possibility of 18O2/16O2 isotopologue separation due to these mass-dependent quantum effects, but it is found that the process is not practical since reasonable selectivities are concomitant with extremely small permeances.

Uniform Synthesis of Bilayer Hydrogen Substituted Graphdiyne for Flexible Piezoresistive Applications

Graphdiyne (GDY) has garnered significant attention as a cutting-edge 2D material owing to its distinctive electronic, optoelectronic, and mechanical properties, including high mobility, direct bandgap, and remarkable flexibility. One of the key challenges hindering the implementation of this material in flexible applications is its large area and uniform synthesis. The facile growth of centimeter-scale bilayer hydrogen substituted graphdiyne (Bi-HsGDY) on germanium (Ge) substrate is achieved using a low-temperature chemical vapor deposition (CVD) method. This material's field effect transistors (FET) showcase a high carrier mobility of 52.6 cm2 V-1 s-1 and an exceptionally low contact resistance of 10 Ω µm. By transferring the as-grown Bi-HsGDY onto a flexible substrate, a long-distance piezoresistive strain sensor is demonstrated, which exhibits a remarkable gauge factor of 43.34 with a fast response time of ≈275 ms. As a proof of concept, communication by means of Morse code is implemented using a Bi-HsGDY strain sensor. It is believed that these results are anticipated to open new horizons in realizing Bi-HsGDY for innovative flexible device applications.