Graphdiyne as Electrode Material: Tuning Electronic State and Surface Chemistry for Improved Electrode Reactivity

Ultra-small CuOx/GDYO nanozyme with boosting peroxidase-like activity via electrochemical strategy: Toward applicable colorimetric detection of organophosphate pesticides

In this paper, an ultra-small-sized CuOx/GDYO nanozyme in situ grown on ITO glass was rationally synthesized from mixed precursors of graphdiyne oxide (GDYO) and copper based infinite coordination polymer (Cu-ICP, consisting of Cu ions and two organic ligands 3,5-di-tert-butylcatechol and 1,4-bis(imidazole-1-ylmethyl)benzene) via mild and simple electrochemical strategy. On one hand, the preferential electro-reduction of Cu-ICP enabled the formation of ultra-small CuOx with Cu(I) as the main component and avoided the loss of oxygen-containing functional groups and defects on the surface of GDYO; on the other hand, GDYO can also serve as electroless reductive species to facilitate the electrochemical deposition of CuOx and turn itself to a higher oxidation state with more exposed functional groups and defects. This one-stone-two-birds electrochemical strategy empowered CuOx/GDYO nanozyme with superior peroxidase-mimicking activity and robust anchoring stability on ITO glass, thus enabled further exploration of the portable device with availability for point-of-use applications. Based on the organophosphorus pesticides (OPs) blocked acetylcholinesterase (AChE) activity, the competitive redox reaction was regulated to initiate the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) catalyzed by CuOx/GDYO peroxidase-like nanozyme, which laid out a foundation for the detection of OPs (with chlorpyrifos as an example). With a detection of limit low to 0.57 nM, the OPs residues during agricultural production can be directly monitored by the portable device we developed.

Ferroptosis-inducing nanomedicine and targeted short peptide for synergistic treatment of hepatocellular carcinoma

The poor prognosis of hepatocellular carcinoma (HCC) is still an urgent challenge to be solved worldwide. Hence, assembling drugs and targeted short peptides together to construct a novel medicine delivery strategy is crucial for targeted and synergy therapy of HCC. Herein, a high-efficiency nanomedicine delivery strategy has been constructed by combining graphdiyne oxide (GDYO) as a drug-loaded platform, specific peptide (SP94-PEG) as a spear to target HCC cells, sorafenib, doxorubicin-Fe2+ (DOX-Fe2+), and siRNA (SLC7A11-i) as weapons to exert a three-path synergistic attack against HCC cells. In this work, SP94-PEG and GDYO form nanosheets with HCC-targeting properties, the chemotherapeutic drug DOX linked to ferrous ions increases the free iron pool in HCC cells and synergizes with sorafenib to induce cell ferroptosis. As a key gene of ferroptosis, interference with the expression of SLC7A11 makes the ferroptosis effect in HCC cells easier, stronger, and more durable. Through gene interference, drug synergy, and short peptide targeting, the toxic side effects of chemotherapy drugs are reduced. The multifunctional nanomedicine GDYO@SP94/DOX-Fe2+/sorafenib/SLC7A11-i (MNMG) possesses the advantages of strong targeting, good stability, the ability to continuously induce tumor cell ferroptosis and has potential clinical application value, which is different from traditional drugs.

Highly Sensitive Near-Field Electrochemical Sensor for In Vivo Monitoring of Respiratory Patterns

Real-time tracking of respiratory patterns provides noninvasive and quick access for evaluating pathophysiological conditions yet remains challenging due to limited temporal resolution and poor sensitivity to dig out fingerprints of respiratory waveforms. Here, we report an electrochemical sensor for accurately tracing respiratory patterns of small animal models based on the electrochemical impedance mechanism for wireless coupling of a graphdiyne oxide (GYDO)-modified sensing coil chip and a reader coil chip via near-field magnetic induction. In the electrochemical impedance measurement mode, an alternating current is applied through the reader coil chip to perturb proton transport at the GYDO interface of the sensing coil chip. As demonstrated, a high-frequency perturbing condition significantly reduces the interfacial resistance for proton transport by 5 orders of magnitude under 95% relative humidity (RH) and improves the low-humidity responses with a limit of detection down to 0.2% RH, enabling in vivo accurate profiling of respiratory patterns on epileptic rats. The electrochemical impedance coupling system holds great potential for new wireless bioelectronics.

Insight into active sites of nitrogen-doped carbon catalyst by stochastic collision electrochemistry

Identifying the active sites of electrocatalysts is important for catalyst design. However, determining the specific active sites of catalysts is still a challenge. Herein, we demonstrate that stochastic collision electrochemistry could be used as a simple but efficient method for identifying the active sites of electrocatalysts, which can overcome the problems caused by the considerable difference between the giant geometric area and the limited exposure of active sites when using traditional cyclic voltammetry. To validate the method, the oxygen reduction reaction and ascorbic acid electrooxidation with the as-synthesized nitrogen-doped carbon catalysts were selected as model reactions. The results show that the pyridinic N dominates the reactivity of the oxygen reduction reaction while the CO functional group is the active site for ascorbic acid oxidation, which could not be identified by cyclic voltammetry with the ensemble drop-casting method. This manuscript demonstrates a new method for identifying the active sites of electrocatalysts, essentially enriching the methodology for identifying active sites.

Multi-Spatiotemporal Probing of Neurochemical Events by Advanced Electrochemical Sensing Methods

Neurochemical events involving biosignals of different time and space dimensionalities constitute the complex basis of neurological functions and diseases. In view of this fact, electrochemical measurements enabling real-time quantification of neurochemicals at multiple levels of spatiotemporal resolution can provide informative clues to decode the molecular networks bridging vesicles and brains. This Minireview focuses on how scientific questions regarding the properties of single vesicles, neurotransmitter release kinetics, interstitial neurochemical dynamics, and multisignal interconnections in vivo have driven the design of electrochemical nano/microsensors, sensing interface engineering, and signal/data processing. An outlook for the future frontline in this realm will also be provided.

Boron-Doped and Ketonic Carbonyl Group-Enriched Graphdiyne as a Dual-Site Carbon Nanozyme with Enhanced Peroxidase-Like Activity

We demonstrate the preparation of a dual-site carbon nanozyme, boron-doped and ketonic carbonyl (-C=O) group-enriched graphdiyne (B-GDY), with an enhanced peroxidase-like activity. Taking advantage of acidic oxidation treatment, GDY oxide (GDYO) with abundant surface oxygen-containing groups is obtained from pristine bulk GDY. Upon further thermal annealing of GDYO with H₃BO₃ under an inert atmosphere, B is introduced into GDY, while the loading of -C=O groups is increased onto B-GDY. We discover that boron-doped and ketonic carbonyl group-enriched graphdiyne as a dual-site carbon nanozyme endows it with an enhanced peroxidase-like activity, which is nearly 4.2-fold higher than that of GDY without B atoms and 6.6-fold higher than that of GDYO without B atoms and with low loading of -C=O groups. The high peroxidase-like activity of B-GDY is ascribed to the dual active sites (-C=O group and B atom) within it, which facilitates the adsorption and decomposition of H₂O₂ into hydroxyl radicals revealed by experimental and theoretical studies. Moreover, B-GDY is successfully employed to develop a colorimetric method for the detection of glucose with good sensitivity and selectivity. This work probes into the intrinsic peroxidase activity and structure-reactivity correlation, creating effective strategies for the preparation of GDY-based nanozymes.

Ultrathin Graphdiyne/Graphene Heterostructure as a Robust Electrochemical Sensing Platform

Graphdiyne (GDY) has been considered as an appealing electrode material for electrochemical sensing because of its alkyne-rich structure and high degrees of π-conjugation, which shows great affinity to heavy metal ions and pollutant molecules via d-π and π-π interactions. However, the low surface area and poor conductivity of bulk GDY limit its electrochemical performance. Herein, a two-dimensional ultrathin GDY/graphene (GDY/G) nanostructure was synthesized and used as an electrode material for electrochemical sensing. Graphene plays the role of an epitaxy template for few-layered GDY growth and conductive layers. The formed few-layered GDY with a high surface area possesses abundant affinity sites toward heavy metal ions (Cd²⁺, Pb²⁺) and toxic molecules, for example, nitrobenzene and 4-nitrophenol, via d-π and π-π interactions, respectively. Moreover, hemin as a key part of the enzyme catalytic motif was immobilized on GDY/G via π-π interactions. The artificial enzyme mimic hemin/GDY/G-modified electrode exhibited promising ascorbic acid and uric acid detection performance with excellent sensitivity and selectivity, a good linear range, and reproducibility. More importantly, real sample detection and the feasibility of this electrochemical sensor as a wearable biosensor were demonstrated.

Three-Mediator Enhanced Collisions on an Ultramicroelectrode for Selective Identification of Single Saccharomyces cerevisiae

Selective detection of colliding entities, especially cells and microbes, is of great challenge in single-entity electrochemistry. Herein, based on the different cellular electron transport pathways between microbes and mediators, we report a three-mediator system [K₃Fe(CN)₆, K₄Fe(CN)₆, and menadione] to achieve redox activity analysis and selective identification of single Saccharomyces cerevisiae without the usage of antibodies. K₄Fe(CN)₆ in the three-mediator system will oxidize near the electrode surface and increase the local concentration of K₃Fe(CN)₆, which will promote the redox reaction of S. cerevisiae. The hydrophobic mediator─menadione─can selectively penetrate through the S. cerevisiae membrane and get access to its intracellular redox center and can further react with K₃Fe(CN)₆ in the bulk solution. In contrast, the mediator can only get access to the bacterial membranes of Escherichia coli and Staphylococcus aureus, which results in different electrochemical collision signals between the above microbes. In the three-mediator system, upward step-like collision signals were observed in S. cerevisiae suspension, which are related to their microbial redox activity. In comparison, E. coli or S. aureus only generated downward current steps because the blockage effect of mediator diffusion suppresses their redox activities. When S. cerevisiae co-existed with E. coli or S. aureus, transients generated by both blockage and redox activity were observed. The approach enables us to trace the collision behaviors of different microbes and distinguish their simultaneous collisions, which is the foundation for further application of electrochemical collision technique in the specific identification of single biological entities.

Graphdiyne Electrochemistry: Progress and Perspectives

Graphdiyne, a carbon allotrope, was synthesized in 2010 for the first time. It consists of two acetylene bonds between adjacent benzene rings. Graphdiyne and its composites thus exhibit ultrahigh intrinsic electrochemical activities. As "star" electrode materials, they have been utilized for various electrochemical applications. With the aim of giving a full screen of graphdiyne electrochemistry, this review starts from the history of graphdiyne materials, followed by their structural and electrochemical features. Recent progress and achievements in the synthesis of graphdiyne materials and their composites are overviewed. Subsequently, various electrochemical applications of graphdiyne materials and their composites are summarized, covering those in the fields of electrochemical energy conversion, electrochemical energy storage, and electrochemical sensing. The perspectives of graphdiyne electrochemistry are also discussed and outlined.

Engineering single-atom catalysts toward biomedical applications

Due to inherent structural defects, common nanocatalysts always display limited catalytic activity and selectivity, making it practically difficult for them to replace natural enzymes in a broad scope of biologically important applications. By decreasing the size of the nanocatalysts, their catalytic activity and selectivity will be substantially improved. Guided by this concept, the advances of nanocatalysts now enter an era of atomic-level precise control. Single-atom catalysts (denoted as SACs), characterized by atomically dispersed active sites, strikingly show utmost atomic utilization, precisely located metal centers, unique metal-support interactions and identical coordination environments. Such advantages of SACs drastically boost the specific activity per metal atom, and thus provide great potential for achieving superior catalytic activity and selectivity to functionally mimic or even outperform natural enzymes of interest. Although the size of the catalysts does matter, it is not clear whether the guideline of "the smaller, the better" is still correct for developing catalysts at the single-atom scale. Thus, it is clearly a new, urgent issue to address before further extending SACs into biomedical applications, representing an important branch of nanomedicine. This review begins by providing an overview of recent advances of synthesis strategies of SACs, which serve as a basis for the discussion of emerging achievements in improving the enzyme-like catalytic properties at an atomic level. Then, we carefully compare the structures and functions of catalysts at various scales from nanoparticles, nanoclusters, and few-atom clusters to single atoms. Contrary to conventional wisdom, SACs are not the most catalytically active catalysts in specific reactions, especially those requiring multi-site auxiliary activities. After that, we highlight the unique roles of SACs toward biomedical applications. To appreciate these advances, the challenges and prospects in rapidly growing studies of SACs-related catalytic nanomedicine are also discussed in this review.

Tailoring Oxygen-Containing Groups on Graphene for Ratiometric Electrochemical Measurements of Ascorbic Acid in Living Subacute Parkinson's Disease Mouse Brains

Ascorbic acid (AA), a major antioxidant in the central nervous system (CNS), is involved in withstanding oxidative stress that plays a significant role in the pathogenesis of Parkinson's disease (PD). Exploring the AA disturbance in the process of PD is of great value in understanding the molecular mechanism of PD. Herein, by virtue of a carbon fiber electrode (CFE) as a matric electrode, a three-step electrochemical process for tailoring oxygen-containing groups on graphene was well designed: potentiostatic deposition was carried out to fabricate graphene oxide on CFE, electrochemical reduction that assisted in removing the epoxy groups accelerated the electron transfer kinetics of AA oxidation, and electrochemical oxidation that increased the content of the carbonyl group (C═O) generated an inner-reference signal. The mechanism was solidified by ab initio calculations by comparing AA absorption on defected models of graphene functionalized with different oxygen groups including carboxyl, hydroxyl, epoxy, and carbonyl. It was found that epoxy groups would hinder the physical absorption of AA onto graphene, while other functional groups would be beneficial to it. Biocompatible polyethylenedioxythiophene (PEDOT) was further rationally assembled to improve the antifouling property of graphene. As a result, a new platform for ratiometric electrochemical measurements of AA with high sensitivity, excellent selectivity, and reproducibility was established. In vivo determination of AA levels in different regions of living mouse brains by the proposed method demonstrated that AA decreased remarkably in the hippocampus and cortex of a subacute PD mouse than those of a normal mouse.

Redox probe-based amperometric sensing for solid-contact ion-selective electrodes

The transformation from the traditional potentiometric response of an ion-selective electrode (ISE) to other signal readout is promising to realize the potential signal amplification. In this work, the redox probes, including ferrocyanide/ferricyanide (Fe(CN)₆^3-/4-), hexaammineruthenium (Ru(NH₃)₆³⁺) and ferrocene derivatives, were introduced to read out the potentiometric response for the solid-contact Ca²⁺-ISE. The mechanism is that the oxidation current of the redox probe on a glassy carbon electrode is modulated by the potential of the ISE through changing the concentrations/activities of Ca²⁺ under the control of the constant applied potential. Results show that the linear range and the slope sensitivity for detection Ca²⁺ by using the amperometric signal based on Fe(CN)₆^4-/3- redox probe are adjustable through changing the applied potentials. Moreover, the redox probe-based amperometric signal for the solid-contact Ca²⁺-ISE is found to be related to both of the types of the redox probes and the electrode areas. This work provides a convenient and general method for translating the potential response at mV grade to the amperometric signal at the μA level, and is promising for detection of ions with high sensitivity by using the ISEs.

Post-modified Strategies of Graphdiyne for Electrochemical Applications

The new carbon material graphdiyne (GDY) has been verified to have a great application prospect in electrochemical field. In order to study its properties and expand its scope of application, various experiments including structural control tests are imposed on GDY. Among them, as one of the most commonly used methods to modify the structure, heteroatom doping is favored for its advantages in synthesis methods and the control of mechanical, electrical and even magnetic properties of carbon materials. According to the published studies, the top-down methods of doping heteroatoms for GDY only need cheap raw materials, simple synthetic route and strong controllability, which is conducive to rapid performance breakthroughs in electrochemical applications. This review selects the typical cases in the development of that post-modification method from the application of GDY in the electrochemical field. Here, based on the existed reports, the commonly used non-metal elements (such as nitrogen, sulfur) and metal elements (such as iron) have been introduced to post-modify GDY. Then, a detailed analysis is made for corresponding electrochemical applications, such as energy storage and electrocatalysis. Finally, the challenges and prospects of post-modified GDY in synthesis and electrochemical applications are proposed. This review provides us a useful guidance for the development of high-quality GDY suitable for electrochemical applications.

Nitrogen-Doped Graphdiyne as a Robust Electrochemical Biosensing Platform for Ultrasensitive Detection of Environmental Pollutants

Owing to its unique chemical structure, natural pores, high structure defects, good surface hydrophilicity and biocompatibility, and favorable electrical conductivity, nitrogen-doped graphdiyne (NGDY) has been attracting attention in the application of electrochemical sensing. Taking advantage of these fascinating electrochemical properties, for the first time, two types of electrochemical enzymatic biosensors were fabricated for the respective detection of organophosphorus pesticides (OPs) and phenols based on the immobilization of acetylcholinesterase or tyrosinase with NGDY. Results revealed that the sensitivities of the NGDY-based enzymatic biosensors were almost twice higher than that of the matching biosensor in the absence of NGDY, proving that NGDY plays a vital role in immobilizing the enzymes and improving the performance of the fabricated biosensors. The effects of nitrogen doping on improving the biosensing performance were studied in depth. Graphitic N atoms can enhance the electrical conductivity, while imine N and pyridinic N can help to adsorb and accumulate the substance molecules to the electrode surface, all of which contribute to the significantly improved performance. Furthermore, these two types of biosensors also demonstrated excellent reproducibility, high stability, and good recovery rate in real environmental samples, which showed a valuable way for the rapid detection of OPs and phenols in the environment. With these excellent performances, it is strongly anticipated that NGDY has tremendous potential to be applied to many other biomedical and environmental fields.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Advances on Graphyne-Family Members for Superior Photocatalytic Behavior

Graphyne (GY) and graphdiyne (GDY) have been employed in photocatalysis since 2012, presenting intriguing electronic and optical properties, such as high electron mobility and intrinsic bandgap due to their high π-conjugated structures. Authors are reporting the enhanced photocatalytic efficiency of these carbon allotropes when combined with different metal oxides or other carbon materials. However, the synthesis of graphyne-family members (GFMs) is still very recent, and not much is known about the true potential of these photocatalytic materials. In this review article, the implications of different synthesis routes on the structural features and photocatalytic properties of these materials are elucidated. The application of GFMs in the nicotinamide adenine dinucleotide (NADH) regeneration, hydrogen and oxygen evolution, and carbon dioxide reduction is discussed, as well as in the degradation of pollutants and bacteria inactivation in water and wastewater treatment.

Ag2S/Ag Nanoparticle Microelectrodes for In Vivo Potentiometric Measurement of Hydrogen Sulfide Dynamics in the Rat Brain

Hydrogen sulfide (H₂S) plays a pivotal role in gas signal transduction, neuroprotection, and regulation of physiological and pathological processes. However, in vivo tracking the dynamic of hydrogen sulfide in the complex brain environment still faces huge challenges. This study demonstrates a new potentiometric method to monitor in vivo the dynamics of hydrogen sulfide in the rat brain using silver nanoparticles (AgNPs)-modified carbon fiber microelectrodes (AgNPs/CFE) pretreated with Na₂S (i.e., Ag₂S/AgNPs/CFE), which acts as a solid-contact and ion-selective microelectrode. The Ag₂S/AgNPs/CFE exhibits good potential response toward hydrogen sulfide in the range of 2.5-160 μM, with a detection limit of 0.8 μM. Because of the presence of Ag₂S, the Ag₂S/AgNPs/CFE shows good selectivity to hydrogen sulfide, avoiding the interference from coexistent electroactive neurochemicals and the analogies, such as ascorbic acid and cysteine in the central nervous system. This good selectivity combined with the reversibility, protein antifouling, and biocompatibility of the microelectrode enables the Ag₂S/AgNPs/CFE to detect hydrogen sulfide in the rat brain during local microinfusion of Na₂S and the change in pH. Our study provides a reliable method to track hydrogen sulfide selectively in vivo, which will help to explore the function of hydrogen sulfide in neurophysiology and pathology.

Subsequent monitoring of ferric ion and ascorbic acid using graphdiyne quantum dots-based optical sensors

Graphdiyne (GDY) as an emerging carbon nanomaterial has attracted increasing attention because of its uniformly distributed pores, highly π-conjugated, and tunable electronic properties. These excellent characteristics have been widely explored in the fields of energy storage and catalysts, yet there is no report on the development of sensors based on the outstanding optical property of GDY. In this paper, a new sensing mechanism is reported built upon the synergistic effect between inner filter effect and photoinduced electron transfer. We constructed a novel nanosensor based upon the newly-synthesized nanomaterial and demonstrated a sensitive and selective detection for both Fe³⁺ ion and ascorbic acid, enabling the measurements in real clinical samples. For the first time fluorescent graphdiyne oxide quantum dots (GDYO-QDs) were prepared using a facile ultrasonic protocol and they were characterized with a range of techniques, showing a strong blue-green emission with 14.6% quantum yield. The emission is quenched efficiently by Fe³⁺ and recovered by ascorbic acid (AA). We have fabricated an off/on fluorescent nanosensors based on this unique property. The nanosensors are able to detect Fe³⁺ as low as 95 nmol L^-1 with a promising dynamic range from 0.25 to 200 μmol L^-1. The LOD of AA was 2.5 μmol L^-1, with range of 10-500 μmol L^-1. It showed a promising capability to detect Fe³⁺ and AA in serum samples. Graphical abstract.

2D graphdiyne: an excellent ultraviolet nonlinear absorption material

With an sp2-hybridized carbon atom structure, graphene is recognized as a nonlinear absorption (NLA) material, which has motivated scientists to explore new allotropes of carbon. Different from graphene, graphdiyne (GDY) consists of sp- and sp2-hybridized carbon atoms. An sp-hybridized carbon-carbon triple bond structure will bring in novel nonlinear optical properties, which are different from other allotropes of carbon. In this study, we investigated the broadband NLA properties (ultraviolet-infrared waveband) of GDY nanosheets, exfoliated using a liquid-phase exfoliation (LPE) method. The short ultraviolet cut-off wavelength (around 200 nm-220 nm) forebodes the potential application of GDY as an ultraviolet optical material. The outstanding NLA resulting in an ultraviolet waveband attests that the GDY nanosheets are veritable ultraviolet NLA materials, which have potential applications in ultraviolet optics. Our study broadens the application scopes of nanomaterials.

Simultaneous multi-signal quantification for highly precise serodiagnosis utilizing a rationally constructed platform

Serodiagnosis with a single quantification method suffers from high false positive/negative rates. In this study, a three-channel platform with an accessional instrumented system was constructed for simultaneous electrochemical, luminescent, and photothermal quantification of H₂S, a bio-indicator for acute pancreatitis (AP) diagnosis. Utilizing the specific reaction between platform and H₂S, the three-channel platform showed high sensitivity and selectivity in the biological H₂S concentration range. The three-channel platform was also feasible for identifying the difference in the plasma H₂S concentrations of AP and normal mice. More importantly, the precision of AP serodiagnosis was significantly improved (>99.0%) using the three-signal method based on the three-channel platform and an optimized threshold, which was clearly higher than that of the single- or two-signal methods (79.5%–94.1%). Our study highlights the importance of constructing a multichannel platform for the simultaneous multi-signal quantification of bio-indicators, and provides rigorous ways to improve the precision of medical serodiagnosis.

Single channel detection methods often suffer from false positives when analysing biological samples. Here, the authors report on the development of a three-channel detection device for measuring hydrogen sulphide in serum and demonstrate application in an in vivo model.

Graphdiyne-Based Materials: Preparation and Application for Electrochemical Energy Storage

Graphdiyne (GDY) has drawn much attention for its 2D chemical structure, extraordinary intrinsic properties, and wide application potential in a variety of research fields. In particular, some structural features and basic physical properties including expanded in-plane pores, regular nanostructuring, and good transporting properties make GDY a promising candidate for an electrode material in energy-storage devices, including batteries and supercapacitors. The chemical structure, synthetic strategy, basic chemical-physical properties of GDY, and related theoretical analysis on its energy-storage mechanism are summarized here. Moreover, through a view of the mutual promotion between the structure modification of GDY and the corresponding electrochemical performance improvement, research progress on the application of GDY for electrochemical energy storage is systematically explored and discussed. Furthermore, the development trends of GDY in energy-storage devices are also comprehensively assessed. GDY-based materials represent a bright future in the field of electrochemical energy storage.

Aptamer superstructure-based electrochemical biosensor for sensitive detection of ATP in rat brain with in vivo microdialysis

Highly sensitive and selective sensing of ATP in rat brain has attracted increasing interest from interdisciplinary fields of analytical chemistry and neuroscience owing to the importance of ATP in cellular metabolism and signal transduction. Herein, we demonstrated an electrochemical biosensor having an aptamer superstructure as a recognition element for the selective and sensitive detection of ATP in rat brain. Unlike the electrochemical aptamer-based sensors (aptasensors) built by assembling a simple DNA structure containing only one aptamer unit onto the electrode substrate, the aptasensor described here was developed by assembling an aptamer superstructure consisting of consecutive aptamer units in DNA strands onto the electrode substrate. Each aptamer unit in the superstructure was labelled with an electrochemical probe (i.e., methylene blue, MB) for signal readout. The aptamer superstructure was assembled onto the surface of a gold electrode to form the electrochemical aptasensor. In the presence of ATP, the strong electrochemical signals produced by multiple redox molecules labeled on the aptamer units clearly decreased because of the disassembling of the aptamer superstructure from the electrode surface due to strong interactions between ATP and the aptamer units. In this approach, the aptasensor was well responsive to the ATP concentration, and the current decrease was linearly related to the ATP concentration ranging from 0.1 nM to 1 mM. Moreover, the aptasensor has high selectivity and good regenerability. Due to these properties, the aptasensor with an aptamer superstructure can exhibit practical applications for ATP assay in rat brain combined with in vivo microdialysis.

Structural Characterization and Identification of Graphdiyne and Graphdiyne-Based Materials

Graphdiyne (GDY) is a two-dimensional (2D) carbon allotrope consisting of sp²- and sp-hybridized carbon atoms. It and GDY-based materials have tremendous application potentials in the fields of catalysis, energy, sensor, electronics and optoelectronics because of their excellent chemical and physical properties. Thus, the explorations to synthesize high-quality GDY and GDY-based materials and to reveal the relationship between their structures and properties are of significance, in which their structural characterization and identification are a crucial step. In this review, we focus on advanced structural characterization techniques and results on GDY, GDY derivatives, GDY composites and doped GDY, including scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray absorption spectroscopy (XAS), electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDS). This review can provide a systemic understanding of the structural characterization and identification of GDY and GDY-based materials and help their development for high-performance applications.

Graphdiyne-Promoted Highly Efficient Photocatalytic Activity of Graphdiyne/Silver Phosphate Pickering Emulsion Under Visible-Light Irradiation

As a new kind of two-dimensional carbon allotrope, graphdiyne (GDY) consists of sp- and sp²-hybridized carbon atoms and has recently been used for developing highly efficient photocatalytic systems because of its unique properties. In this study, we find that GDY can form a Pickering emulsion with silver phosphate (Ag₃PO₄) nanoparticles that exhibits largely enhanced photocatalytic activity in the visible-light region. In this system, Ag₃PO₄ acts as a photocatalytically active semiconductor with GDY as the hydrophobic nanostructure. Photocatalytic activity of the Ag₃PO₄/GDY-based Pickering emulsion toward the photodegradation of methylene blue (MB) and photooxidation of water is investigated under visible-light irradiation. Compared to previous Ag₃PO₄/CNT- or Ag₃PO₄/graphene-based Pickering emulsions, the Ag₃PO₄/GDY-based emulsion efficiently catalyzes MB degradation with a higher apparent rate constant k being ∼0.477 min^-1, while for water oxidation its photocatalytic activity is also improved by 1.89 and 1.75 times, respectively. Such an enhancement in the photocatalytic activity is mainly ascribed to the capability of GDY in acting as an acceptor of the photogenerated electrons from Ag₃PO₄ nanoparticles and in facilitating the hole transportation as well as in reducing Ag⁺ to Ag⁰. This study demonstrates that GDY is a new candidate with a promising future in developing photocatalytic systems with high efficiency for real applications.