Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance

Fabricating Graphene-Based Molecular Electronics via Surface Modification by Physisorption and Chemisorption

Graphene, a one-atom-thick sp2-hybridized carbon sheet, has enormous potential for fabricating flexible transparent electronics due to its unique electronic and mechanical properties. However, the intrinsic lack of a band gap, the low reactivity, and the poor solubility of pristine graphene have largely hindered wide-ranging applications so far. One of the most attractive ways to resolve these issues is to modify the graphene surface through molecular physisorption or chemisorption. In this review, we summarize the recent progress in fabricating graphene-based molecular electronics through manipulating small functional molecules on the graphene surface towards chemical reactivity adjustment, molecular doping, and band gap opening via non-covalent and covalent interactions, and draw attention to challenges and opportunities. We also suggest future research directions for graphene-based molecular electronics.

Experimental and Theoretical Investigation of the Formation of Daidzein Ion-pair Compounds: Solubility, Hydrogen Bonds, Stability

Ion pairs represent a robust molecular force arising from the union of oppositely charged ions, held together by Coulomb attraction. Daidzein (Dai), categorized as a BCS IV drug, faces limitations in clinical application due to its relatively low solubility. To enhance the drug's solubility, a Dai ion pair was prepared, and the mechanism underlying ion-pair formation was investigated. A comprehensive approach, combining experimental techniques and theoretical calculations, such as scanning electron microscopy, powder X-ray diffraction, differential scanning calorimetry, Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray Photoelectron Spectroscopy, and computational simulation was employed to explore the ion-pair formation mechanism. The findings indicate a significant improvement in Dai solubility through the preparation of Arg and Lys ion-pair compounds. The results revealed that the Dai-Lys ion pair exhibited more short hydrogen bonds and fewer long hydrogen bonds than did the Dai-Arg ion pair, strengthening the intermolecular interactions and improving crystal structure stability. This study effectively enhanced the solubility of Dai and offers valuable insights into the mechanisms underlying ion pair formation in ionizable drugs.

Carbon-Based Nanomaterials Decorated Electrospun Nanofibers in Biosensors: A Review

Nanomaterials have revolutionized scientific research due to their exceptional physical and chemical capabilities. Carbon-based nanomaterials such as graphene and its derivates have excellent electrical, optical, thermal, physical, and chemical properties that have made them indispensable in several industries worldwide, including medicine, electronics, and energy. By incorporating carbon-based nanomaterials as nanofillers in electrospun nanofibers (ESNFs), smoother and highly conductive nanofibers can be achieved that possess a large surface area and porosity. This approach provides a superior alternative to traditional materials in the development of improved biosensors. Carbon-based ESNFs, among the most exciting new-generation materials, have many applications, including filtration, pharmaceuticals, biosensors, and membranes. The electrospinning technique is a highly efficient and cost-effective method for producing desired nanofibers compared to other methods. Various types of natural and synthetic organic polymers have been successfully utilized in solution electrospinning to produce nanofibers directly. To create diagnostics devices, various biomolecules like antibodies, enzymes, aptamers, ligands, and even cells can be bound to the surface of nanofibers. Electrospun nanofibers can serve as an immobilization matrix to create a biofunctional surface. Thus, biosensors with desired features can be produced in this way. This study comprehensively reviews biosensors that integrate nanodiamonds, fullerenes, carbon nanotubes, graphene oxide, and carbon dots into electrospun nanofibers.

Photophysical characterization of tetrahydroxyphenyl porphyrin Zn(II) and V(IV) complexes: experimental and DFT study

Photodynamic therapy (PDT) is a promising technique for the treatment of various diseases. In this sense, the singlet oxygen quantum yield (Φ∆) is a physical-chemical property that allows to stablish the applicability of a potential photosensitizers (PS) as a drug for PDT. In the herein report, the Φ∆ of three photosensitizers was determined: metal-free tetrahydroxyphenyl porphyrin (THPP), THPP-Zn and the THPP-V metal complexes. Their biological application was also evaluated. Therefore, the in vitro study was carried out to assess their biological activity against Escherichia coli. The metal-porphyrin complexes exhibited highest activities against the bacterial strain Escherichia coli. at the highest concentration (175 μg/mL) and show better activity than the free base ligand (salts and blank solution). Results indicated a relation between Φ∆ and the inhibitory activity against Escherichia coli, thus, whereas higher is the Φ∆, higher is the inhibitory activity. The values of the Φ∆ and the inhibitory activity follows the tendency THPP-Zn > THPP > THPP-V. Furthermore, quantum chemical calculations allowed to gain deep insight into the electronic and optical properties of THPP-Zn macrocycle, which let to verify the most probable energy transfer pathway involved in the singlet oxygen generation.

Porphyrin as a Cryoprotectant for Graphene Oxide-Coated Gold Nanorods to Produce Conjugated Product with Improved Stability and Opto-Phototherapeutic Properties

Graphene oxide (GO) as a coating material for gold nanorods (AuNRs) has gained interest in reducing toxicity and improving the photothermal profiling of AuNRs. However, there is still a challenge regarding the storage of colloidal suspensions of GO-coated AuNRs (GO@AuNRs). Hence, the conjugation of GO@AuNRs to meso-tetra-(4-sulfonatophenyl)porphyrin (TPPS4), an anionic water-soluble porphyrin, has been reported to enhance their re-dispensability and improve their phototherapeutic properties. The AuNRs and GO were synthesised using seed-mediated and Hummers' methods, respectively. The GO@AuNRs were conjugated to TPPS4 and characterised using ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, zeta analyser, dynamic light scattering (DLS), photoluminescence spectroscopy (PL), x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Fourier-transform infrared spectroscopy (FTIR) before freeze-drying. The results showed that the AuNRs were sandwiched between GO and TPPS4. After freeze-drying, the freeze-dried conjugate was dispensed in deionised water without adding cryoprotectants and its properties were compared to those of the unfreeze-dried conjugate. The results showed that the freeze-dried conjugate contained similar optical properties to the unfreeze-dried conjugate. However, the bare GO@AuNRs showed a change in the optical properties after freeze-drying. These results revealed that porphyrin is an excellent additive to reduce the freeze-drying stress tolerance of GO@AuNRs. The freeze-dried conjugate also showed both singlet oxygen and photothermal properties of GO@AuNRs and porphyrin. These results indicated that the freeze-dried conjugate is a promising dual photodynamic and photothermal agent, and porphyrin can act as a cryoprotectant.

Noncovalent Self-Assembly of Single-Layer MoS2 Nanosheets and Zinc Porphyrin into Stable SURMOF Nanohybrids with Multimodal Photocatalytic Properties

A noncovalent integration of nanosheets of molybdenum disulfide (MoS2) and the zinc porphyrin complex Zn(II) 5,10,15,20-tetrakis(4-carboxyphenyl)porphine (ZnTCPP) through coordination bonding with metal clusters of zinc acetate (Zn[OAc]2) was applied for synthesis of stable hybrid nanomaterial avoiding surface prefunctionalization. The X-ray powder diffraction in combination with the BET nitrogen adsorption method confirms formation of a ZnTCPP-based surface-attached metal-organic framework (SURMOF) with micropores of 1.63 nm on the MoS2 nanosheets. Fluorescence spectroscopy confirmed Forster resonance energy transfer (FRET) between MoS2 and ZnTCPP without contact quenching. Fluorescent trapping with terephthalic acid for hydroxyl radicals and Sensor Green for singlet oxygen was applied for studying the pathways of photodegradation of model organic pollutant 1,5-dihydroxynaphthalene (DHN) in the presence of SURMOF/MoS2. Visible light initiates sensitization through the excitation of ZnTCPP generating singlet oxygen, whereas UV-light promotes either aerobic FRET-mediated "Z scheme" or anaerobic "Type II heterojunction" mechanisms. Owing to its multimodal photochemistry, the SURMOF/MoS2 hybrid showed comparatively high photocatalytic activity in UV-assisted degradation of DHN (keffUV = 4.0 × 10-2 min-1) as well as the antibacterial activity confirmed by E. coli survival test under visible light. Noncovalent self-assembly utilizing coordination bonding in SURMOFs as supramolecular adhesive to avoid surface premodification provides a basis for new types of multicomponent nanosystems with switchable functionalities by combining different 2D materials and chromophores in one hybrid structure.

Graphene performs the role of an electron donor in covalently interfaced porphyrin-boron azadipyrromethene dyads and manages photoinduced charge-transfer processes

Herein, we introduced the versatility of free-base and zinc-metallated porphyrin (H₂P and ZnP, respectively) to combine with boron azadipyrromethene (azaBDP) NIR absorbing species, for extending their photophysical interest and covalently anchored onto graphene. In particular, the covalent functionalization of graphene with those H₂P-azaBDP and ZnP-azaBDP dyads ensured an invariable structure, in which both chromophores and graphene are in intimate contact, free of aggregations and impurities. Both H₂P-azaBDP and ZnP-azaBDP dyads were found to perform energy transfer processes between the chromophores, however, only ZnP-azaBDP confirmed additional charge separation between the chromophores yielding the ZnP˙⁺-azaBDP˙^- charge-separated state. On the other hand, graphene in (H₂P-azaBDP)-graphene and (ZnP-azaBDP)-graphene hybrids was found to act as an electron donor, yielding (H₂P-azaBDP˙^-)-graphene˙⁺ and (ZnP-azaBDP˙^-)-graphene˙⁺ charge-separated states at an ultrafast timescale. The creation of such donor-acceptor systems, featuring graphene as an electron donor and Vis-to-NIR electron-acceptor dyads, expands their utility when considered in optoelectronic applications.

Visible-Light Assisted Covalent Surface Functionalization of Reduced Graphene Oxide Nanosheets with Arylazo Sulfones

We present an environmentally benign methodology for the covalent functionalization (arylation) of reduced graphene oxide (rGO) nanosheets with arylazo sulfones. A variety of tagged aryl units were conveniently accommodated at the rGO surface via visible-light irradiation of suspensions of carbon nanostructured materials in aqueous media. Mild reaction conditions, absence of photosensitizers, functional group tolerance and high atomic fractions (XPS analysis) represent some of the salient features characterizing the present methodology. Control experiments for the mechanistic elucidation (Raman analysis) and chemical nanomanipulation of the tagged rGO surfaces are also reported.

Tuning the Chemical and Mechanical Properties of Conductive MoS2 Thin Films by Surface Modification with Aryl Diazonium Salts

Molybdenum disulfide (MoS2) is a promising material for applications in sensors, energy storage, energy conversion devices, solar cells, and fuel cells. Because many of those applications require conductive materials, we recently developed a method for preparing a conductive form of MoS2 (c-MoS2) using dilute aqueous hydrogen peroxide in a simple and safe way. Here, we investigate modulating the chemical and mechanical surface properties of c-MoS2 thin films using diazonium chemistry. In addition to a direct passivation strategy of c-MoS2 with diazonium salts for electron-withdrawing groups, we also propose a novel in situ synthetic pathway for modification with electron-donating groups. The obtained results are examined by Raman spectroscopy and X-ray photoelectron spectroscopy. The degree of surface passivation of pristine and functionalized c-MoS2 films was tested by exposing them to aqueous solutions of different metal cations (Fe2+, Zn2+, Cu2+, and Co2+) and detecting the chemiresistive response. While pristine films were found to interact with several of the cations, modified films did not. We propose that a surface charge transfer mechanism is responsible for the chemiresistive response of the pristine films, while both modification routes succeeded at complete surface passivation. Functionalization was also found to lower the coefficient of friction for semiconducting 2H-MoS2, while all conductive materials (modified or not) also had lower coefficients of friction. This opens up a pathway to a palette of dry lubricant materials with improved chemical stability and tunable conductivity. Thus, both in situ and direct diazonium chemistries are powerful tools for tuning chemical and mechanical properties of conductive MoS2 for new devices and lubricants based on conductive MoS2.

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

Food safety monitoring assays based on synthetic recognition structures such as aptamers are receiving considerable attention due to their remarkable advantages in terms of their ability to bind to a wide range of target analytes, strong binding affinity, facile manufacturing, and cost-effectiveness. Although aptasensors for food monitoring are still in the development stage, the use of an electrochemical detection route, combined with the wide range of materials available as transducers and the proper immobilization strategy of the aptamer at the transducer surface, can lead to powerful analytical tools. In such a context, employing aryldiazonium salts for the surface derivatization of transducer electrodes serves as a simple, versatile and robust strategy to fine-tune the interface properties and to facilitate the convenient anchoring and stability of the aptamer. By summarizing the most important results disclosed in the last years, this article provides a comprehensive review that emphasizes the contribution of aryldiazonium chemistry in developing electrochemical aptasensors for food safety monitoring.

Functionalization of Graphene Oxide with Porphyrins: Synthetic Routes and Biological Applications

Among the available carbon nanomaterials, graphene oxide (GO) has been widely studied because of the possibility of anchoring different chemical species for a large number of applications, including those requiring water-compatible systems. This Review summarizes the state-of-the-art of synthetic routes used to functionalize GO, such as those involving multiple covalent and non-covalent bonds to organic molecules, functionalization with nanoparticles and doping. As a recent development in this field, special focus is given to the formation of nanocomposites comprising GO and porphyrins, and their characterization through spectroscopic techniques (such as UV-Vis, fluorescence, Raman spectroscopy), among others. The potential of such hybrid systems in targeted biological applications is also discussed, namely for cancer therapies relying on photodynamic and photothermal therapies and for the inhibition of telomerase enzyme. Lastly, some promising alternative materials to GO are presented to overcome current challenges of GO-based research and to inspire future research directions in this field.

Building Tailored Interfaces through Covalent Coupling Reactions at Layers Grafted from Aryldiazonium Salts

Aryldiazonium ions are widely used reagents for surface modification. Attractive aspects of their use include wide substrate compatibility (ranging from plastics to carbons to metals and metal oxides), formation of stable covalent bonding to the substrate, simplicity of modification methods that are compatible with organic and aqueous solvents, and the commercial availability of many aniline precursors with a straightforward conversion to the active reagent. Importantly, the strong bonding of the modifying layer to the surface makes the method ideally suited to further on-surface (postfunctionalization) chemistry. After an initial grafting from a suitable aryldiazonium ion to give an anchor layer, a target species can be coupled to the layer, hugely expanding the range of species that can be immobilized. This strategy has been widely employed to prepare materials for numerous applications including chemical sensors, biosensors, catalysis, optoelectronics, composite materials, and energy conversion and storage. In this Review our goal is first to summarize how a target species with a particular functional group may be covalently coupled to an appropriate anchor layer. We then review applications of the resulting materials.

Mesoporous carbon nitride supported 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine cobalt(ii) as a selective and durable electrocatalyst for the production of hydrogen peroxide via two-electron oxygen reduction

Stability and efficiency of CoTMPP@MCN along with the general strategy for tuning the active site.

Homogeneous and heterogeneous molecular catalysts for electrochemical reduction of carbon dioxide

Carbon dioxide (CO2) is a greenhouse gas whose presence in the atmosphere significantly contributes to climate change. Developing sustainable, cost-effective pathways to convert CO2 into higher value chemicals is essential to curb its atmospheric presence. Electrochemical CO2 reduction to value-added chemicals using molecular catalysis currently attracts a lot of attention, since it provides an efficient and promising way to increase CO2 utilization. Introducing amino groups as substituents to molecular catalysts is a promising approach towards improving capture and reduction of CO2. This review explores recently developed state-of-the-art molecular catalysts with a focus on heterogeneous and homogeneous amine molecular catalysts for electroreduction of CO2. The relationship between the structural properties of the molecular catalysts and CO2 electroreduction will be highlighted in this review. We will also discuss recent advances in the heterogeneous field by examining different immobilization techniques and their relation with molecular structure and conductive effects.

Well-Designed Au Nanorod-Doped Cu2O Core-Shell Nanocube-Embedded Reduced Graphene Oxide Composite for Efficient Removal of a Water Pollutant Dye

To ensure environmental safety, the removal of organic pollutants has gained increasing attention globally. We have synthesized uniform Au nanorod (NR)-doped Cu₂O core-shell nanocubes (CSNCs) via a seed-mediated route embedded on the surface of rGO sheets. The Au NRs@Cu₂O/rGO nanocomposite was characterized using various techniques such as transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FT-IR) and Raman spectroscopies. The scanning TEM-energy-dispersive spectroscopy (STEM-EDS) elemental mapping of the AuNRs@Cu₂O/rGO nanocomposite indicates that the Au NR (40 nm) is fully covered with the Cu₂O particles (∼145 nm) as a shell. N₂ gas sorption analysis shows that the specific surface area of the composite is 205.5 m²/g with a mesoporous character. Moreover, incorporation of Au NRs@Cu₂O CSNCs increases the nanogaps around the nanoparticles and suppresses the stacking/bundling of rGO, which significantly influences the pore size and increase the surface area. A batch adsorption experiment was carried out under various parameters, such as the effect of pH, contact time, temperature, initial dye concentration, and adsorbent dosage, for the removal of methylene blue (MB) in aqueous solution. The high surface area and mesoporosity can cause the adsorption capacity to reach equilibrium within 20 min with a 99.8% removal efficiency. Both kinetic and isotherm data were obtained and fitted very well with the pseudo-second-order kinetic and Langmuir isotherm model. The Langmuir isotherm revealed an excellent dye sorption capacity of 243.9 mg/g at 298 K. Moreover, after five adsorption cycles, the dye removal efficiency decreased from 99 to 86%. This novel route paves a new path for heterogeneous adsorbent synthesis, which is useful for catalysis and electrochemical applications.

Robust Magnetized Graphene Oxide Platform for In Situ Peptide Synthesis and FRET-Based Protease Detection

Graphene oxide (GO)/peptide complexes as a promising disease biomarker analysis platform have been used to detect proteolytic activity by observing the turn-on signal of the quenched fluorescence upon the release of peptide fragments. However, the purification steps are often cumbersome during surface modification of nano-/micro-sized GO. In addition, it is still challenging to incorporate the specific peptides into GO with proper orientation using conventional immobilization methods based on pre-synthesized peptides. Here, we demonstrate a robust magnetic GO (MGO) fluorescence resonance energy transfer (FRET) platform based on in situ sequence-specific peptide synthesis of MGO. The magnetization of GO was achieved by co-precipitation of an iron precursor solution. Magnetic purification/isolation enabled efficient incorporation of amino-polyethylene glycol spacers and subsequent solid-phase peptide synthesis of MGO to ensure the oriented immobilization of the peptide, which was evaluated by mass spectrometry after photocleavage. The FRET peptide MGO responded to proteases such as trypsin, thrombin, and β-secretase in a concentration-dependent manner. Particularly, β-secretase, as an important Alzheimer's disease marker, was assayed down to 0.125 ng/mL. Overall, the MGO platform is applicable to the detection of other proteases by using various peptide substrates, with a potential to be used in an automated synthesis system operating in a high throughput configuration.

Exfoliation of 2D Materials for Energy and Environmental Applications

The fascinating properties of single-layer graphene isolated by mechanical exfoliation have inspired extensive research efforts toward two-dimensional (2D) materials. Layered compounds serve as precursors for atomically thin 2D materials (briefly, 2D nanomaterials) owing to their strong intraplane chemical bonding but weak interplane van der Waals interactions. There are newly emerging 2D materials beyond graphene, and it is becoming increasingly important to develop cost-effective, scalable methods for producing 2D nanomaterials with controlled microstructures and properties. The variety of developed synthetic techniques can be categorized into two classes: bottom-up and top-down approaches. Of top-down approaches, the exfoliation of bulk 2D materials into single or few layers is the most common. This review highlights chemical and physical exfoliation methods that allow for the production of 2D nanomaterials in large quantities. In addition, remarkable examples of utilizing exfoliated 2D nanomaterials in energy and environmental applications are introduced.

Mechanism and Improved Dissolution of Glycyrrhetinic Acid Solid Dispersion by Alkalizers

The purpose of this study was to increase the dissolution of glycyrrhetinic acid (GA) by preparing ternary solid dispersion (TSD) systems containing alkalizers, and to explore the modulating mechanism of alkalizers in solid dispersion systems. GA TSDs were prepared by hot melt extrusion (HME) with Kollidon^® VA64 as the carrier and L-arginine/meglumine as the alkalizers. The in vitro release of the TSD was investigated with a dissolution test, and the dissociation constant (pKa) was used to describe the ionization degree of the drug in different pH buffers. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectra, X-ray photoelectron spectroscopy (XPS), and a molecular model were used for solid-state characterizations and to study the dissolution mechanism of the TSDs. It was evident that the dissolution of GA significantly increased as a result of the TSD compared to the pure drug and binary solid dispersion. SEM, DSC, and XPRD data showed that GA transformed into an amorphous form in TSD. As illustrated by FTIR, Raman, XPS, and molecular docking, high binding energy ion-pair complexes formed between GA and the alkalizers during the process of HME. These can destroy the H-bond between GA molecules. Further, intermolecular H-bonds formed between the alkalizers and Kollidon^® VA64, which can increase the wettability of the drug. Our results will significantly improve the solubility and dissolution of GA. In addition, the lower pKa value of TSD indicates that higher ionization is beneficial to the dissolution of the drug. This study should facilitate further developments of TSDs containing alkalizers to improve the dissolution of weakly acidic drugs and gain a richer understanding of the mechanism of dissolution.

Recent Advances in Chemical Functionalization of 2D Black Phosphorous Nanosheets

Owing to their tunable direct bandgap, high charge carrier mobility, and unique in-plane anisotropic structure, black phosphorus nanosheets (BPNSs) have emerged as one of the most important candidates among the 2D materials beyond graphene. However, the poor ambient stability of black phosphorus limits its practical application, due to the chemical degradation of phosphorus atoms to phosphorus oxides in the presence of oxygen and/or water. Chemical functionalization is demonstrated as an efficient approach to enhance the ambient stability of BPNSs. Herein, various covalent strategies including radical addition, nitrene addition, nucleophilic substitution, and metal coordination are summarized. In addition, efficient noncovalent functionalization methods such as van der Waals interactions, electrostatic interactions, and cation-π interactions are described in detail. Furthermore, the preparations, characterization, and diverse applications of functionalized BPNSs in various fields are recapped. The challenges faced and future directions for the chemical functionalization of BPNSs are also highlighted.

Boronic acids for functionalisation of commercial multi-layer graphitic material as an alternative to diazonium salts

Commercially obtained plasma-synthesised multi-layer graphene was functionalised with 4-(trifluoromethyl)phenyl groups utilising the corresponding boronic acid providing a safer alternative to diazonium salts.

MoS2 quantum dots chemically modified with porphyrin for solid-state broadband optical limiters

MoS₂ quantum dots (MQDs) with unique electronic and optical properties are promising broadband nonlinear optical (NLO) materials for ultrafast optical applications. It would be very interesting and challenging to functionalize MQDs with another hotspot optoelectronically active molecule "porphyrin". Herein, by treating MQDs with tetraphenylporphyrin (TPP) diazonium salts, we synthesized a novel nanohybrid material, MQD-TPP, in which TPP was covalently functionalized to the surface of MQDs via a C-S linkage. To explore its solid-state broadband NLO application, the MQD-TPP nanohybrid was encapsulated into a poly(methyl methacrylate) (PMMA) matrix for the open-aperture Z-scan measurements at 532 and 1064 nm. In contrast to MQDs/PMMA and TPP/PMMA, the MQD-TPP/PMMA film exhibited superior nonlinear optical and optical limiting responses with the largest nonlinear coefficients (β_eff) and the lowest optical limiting (OL) thresholds of about 1059.17 cm GW^-1 and 1.62 J cm^-2 at 532 nm and 831.13 cm GW^-1 and 1.97 J cm^-2 at 1064 nm, respectively.

Covalent Functionalization of Graphene Oxide with a Presynthesized Metal-Organic Framework Enables a Highly Stable Electrochemical Sensing

This paper reports the covalent functionalization of graphene oxide (GO) by a presynthesized metal-organic framework NH₂-MIL-101(Fe) via ultrasonication of the two components. The formation of Fe-O covalent bonding in the NH₂-MIL-101(Fe)-GO nanohybrid is clearly evidenced, and the covalent bonding still remains after electrochemical reduction. The morphology and structure of the nanohybrid are characterized via scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. The electrode based on electrochemically reduced NH₂-MIL-101(Fe)-GO shows ultrastable and high-sensitive performance in simultaneous electrochemical sensing of three purine metabolic derivatives (uric acid, xanthine, and hypoxanthine); in particular, no signal fading is seen even after running for 120 times. The covalent bonding within the nanohybrid is obviously the key to maintain such a stability.

Interactions between the Aryldiazonium Cations and Graphene Oxide: A DFT Study

Understanding the grafting behavior of the aryldiazonium cations is of fundamental and also of practical importance for the vast number of applications that involve the use of modified graphene oxide (from simple adsorption process to electronic and photovoltaic applications). In this work, the mechanism of the adsorption and grafting of diazonium cations on the graphene oxide surface was investigated by the use of density functional theory. Two types of aryldiazonium cations, one bearing only phenyl ring and the other nitrophenyl, were selected as adsorbates/grafted moiety. By evaluating the adsorption energies at 7 different positions onto the graphene oxide both in the gaseous and solvent phase (using COSMO approach), the most probable adsorption sites were found. Moreover, the most stable adsorption sites were used to calculate and plot NCI (noncovalent interactions). The obtained results are important as they not only give molecular insights regarding the nature of the interaction and its dependence on the adsorption site of the graphene oxide surface but also on the activation energy for such a grafting reaction to take place, providing a mechanistic aspect to understand these grafting reactions.

Reduced graphene oxide-induced crystallization of CuPc interfacial layer for high performance of perovskite photodetectors

TS-CuPc/rGO nanocomposite thin films were synthesized and applied as an interfacial layer for high-performance perovskite-based photodiodes.

Noncovalently copper-porphyrin functionalized reduced graphene oxide for sensitive electrochemical detection of dopamine

The nanocomposite of an electron-deficient flat tetrakis-(ethoxycarbonyl) porphyrin copper(II) (Cu-TECP) and reduced grapheme oxide (RGO) was prepared and used for electrochemical detection of dopamine (DA). The prepared nanocomposite was characterized by scanning electron microscopy, Raman spectroscopy, FT-IR spectroscopy, ultraviolet-visible spectroscopy and electrochemical impedance spectroscopy. Electrochemical studies of the modified glass carbon electrode (GCE) were carried out by the cyclic voltammetry and differential pulse voltammograms (DPV) methods. The RGO/Cu-TECP/GCE exhibited enhanced electrocatalytic activity towards the detection of dopamine (DA). The detection limit was 0.58 μM, while the linear range was from 2 to 200 μM ([Formula: see text] 0.997).

Functionalization of graphene: does the organic chemistry matter?

Reactions applying amidation- or esterification-type processes and diazonium salts chemistry constitute the most commonly applied synthetic approaches for the modification of graphene-family materials. This work presents a critical assessment of the amidation and esterification methodologies reported in the recent literature, as well as a discussion of the reactions that apply diazonium salts. Common misunderstandings from the reported covalent functionalization methods are discussed, and a direct link between the reaction mechanisms and the basic principles of organic chemistry is taken into special consideration.

Graphene and Carbon-Nanotube Nanohybrids Covalently Functionalized by Porphyrins and Phthalocyanines for Optoelectronic Properties

In recent years, there has been a rapid growth in studies of the optoelectronic properties of graphene, carbon nanotubes (CNTs), and their derivatives. The chemical functionalization of graphene and CNTs is a key requirement for the development of this field, but it remains a significant challenge. The focus here is on recent advances in constructing nanohybrids of graphene or CNTs covalently linked to porphyrins or phthalocyanines, as well as their application in nonlinear optics. Following a summary of the syntheses of nanohybrids constructed from graphene or CNTs and porphyrins or phthalocyanines, explicit intraconjugate electronic interactions between photoexcited porphyrins/phthalocyanines and graphene/CNTs are introduced classified by energy transfer, electron transfer, and charge transfer, and their optoelectronic applications are also highlighted. The major current challenges for the development of covalently linked nanohybrids of porphyrins or phthalocyanines and carbon nanostructures are also presented.

Freestanding photocatalytic materials based on 3D graphene and polyporphyrins

A new concept in the formulation of hybrid nanostructured materials combining high quality graphene 3D supported by Nickel foam and polyporphyrins for visible light photocatalytic application is here reported. Our innovative approach involves the development of a freestanding device able to: i) offer a high surface area to bind the photosensitizers by π-π interactions, and ii) enhance stability and photocatalytic efficiency by using cyclic porphyrin polymers. For these purposes, homo- and co-polymerization reactions by using different porphyrin (free or zinc complexed) monomers were performed. The microscopic structures and morphology of graphene polymer nanocomposites were investigated by using Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Atomic Force Microscopy (AFM). Finally, photocatalytic activity under visible light irradiation of the obtained nanocomposites was tested, by using methylene blue (MB) as organic pollutant. The obtained data suggested that hindered cyclic polymeric structures stacked on graphene surface by non-covalent interactions, restrict the formation of non photoactive aggregates and, as a consequence, induce an enhancement of photocatalytic activity. Remarkably, our systems show a degradation efficiency in the visible-light range much higher than other similar devices containing nanoporphyrin units reported in literature.

A nearly perfect spin filter and a spin logic gate based on a porphyrin/graphene hybrid material

We propose experimentally feasible spintronic devices using the porphyrin/graphene hybrid material, and find a nearly perfect spin polarization effect.

Synergistically Enhanced Optical Limiting Property of Graphene Oxide Hybrid Materials Functionalized with Pt Complexes

Recently, graphene-based materials have become well-known nonlinear optical materials for the potential application of laser protection. Two new graphene oxide-platinum  complex (GO-Pt) hybrid materials (GO-Pt-1, GO-Pt-2) have been fabricated through covalent modification and electrostatic adsorption of different Pt complexes with GO. The structural and photophysical properties of the resultant hybrid materials were studied. The nonlinear optical properties and optical power limiting (OPL) performance of Pt complexes, GO, and GO-Pt hybrid materials were investigated by using Z-scan measurements at 532 nm. At the same transmittance, the results illustrate that functionalization of GO makes GO-Pt hybrid materials possess better nonlinear optical properties and OPL performance than individual Pt complexes and GO due to a combination of nonlinear scattering, nonlinear absorption, and photoinduced electron and energy transfer between GO and Pt complex moieties. Furthermore, the nonlinear optics and OPL performance of GO-Pt-2 are better than those of GO-Pt-1, due to not only the excellent optical limiting of Pt-2 and more molecules per area of GO but also the way of combination of Pt-2 and GO.

Cyanographene and Graphene Acid: Emerging Derivatives Enabling High-Yield and Selective Functionalization of Graphene

Efficient and selective methods for covalent derivatization of graphene are needed because they enable tuning of graphene's surface and electronic properties, thus expanding its application potential. However, existing approaches based mainly on chemistry of graphene and graphene oxide achieve only limited level of functionalization due to chemical inertness of the surface and nonselective simultaneous attachment of different functional groups, respectively. Here we present a conceptually different route based on synthesis of cyanographene via the controllable substitution and defluorination of fluorographene. The highly conductive and hydrophilic cyanographene allows exploiting the complex chemistry of -CN groups toward a broad scale of graphene derivatives with very high functionalization degree. The consequent hydrolysis of cyanographene results in graphene acid, a 2D carboxylic acid with pK_a of 5.2, showing excellent biocompatibility, conductivity and dispersibility in water and 3D supramolecular assemblies after drying. Further, the carboxyl groups enable simple, tailored and widely accessible 2D chemistry onto graphene, as demonstrated via the covalent conjugation with a diamine, an aminothiol and an aminoalcohol. The developed methodology represents the most controllable, universal and easy to use approach toward a broad set of 2D materials through consequent chemistries on cyanographene and on the prepared carboxy-, amino-, sulphydryl-, and hydroxy- graphenes.

Design and Syntheses of Novel Fluoroporphyrin-Anthraquinone Complexes as Antitumor Agents

A novel fluoroporphyrin-anthraquinone hybrid with dipeptide link and its metal complexes were synthesized and evaluated for anti-proliferation activity in human cancer cell line HeLa. The preliminary results demonstrated that all the compounds showed moderate to excellent antitumor activities. Among the active compounds, compound 3 which contains fluorinated porphyrin-anthraquinone and zinc ion exhibited the highest potency with IC50 value of 8.83 µM, indicating that it was a promising antitumor candidate.