Facile Electrostatic Self-assembly Research Articles

Biomimetic and electrostatic self-assembled nanocellulose/MXene films constructed with sequential bridging strategy for flexible supercapacitor

Despite the two-dimensional titanium carbide MXene (Ti3C2Tx) has shown promising applications in energy storage, the inherent self-stacking and weak connectivity among nanosheets present a challenge in manufacturing robust MXene films for emerging flexible supercapacitors. Herein, inspired by the robust “soft-hard” structured exoskeletons of crustaceans, the biomimetic cellulose nanofibers (CNFs)/MXene-Al (CM-Al) film with integrated high mechanical toughness, electroconductivity and electrochemical behavior, sequential bridging with hydrogen and ionic bonds, is crafted via the facile electrostatic self-assembly strategy. The embedded CNFs guide the in-plane orientation of MXene through hydrogen bonding, forming a “soft-hard” microstructure and dramatically enhancing the mechanical toughness of CM-Al. The rigid ionic bonds established between the oxygen-containing groups on CNFs and MXene with Al3+ further elevate the mechanical strength (163.88 MPa) and act as additional electron transfer channels to impart the reinforced electroconductivity (82.63 S cm−1). Benefiting from the more active site exposure induced by the expanded MXene layer spacing after CNFs embedding and the weakened intrinsic resistance caused by the constructed ionic bonding, the assembled flexible quasi-solid-state symmetric supercapacitor with CM-Al as electrode delivers a high area capacitance (679 mF cm−2), energy density (16.2 μWh cm−2), cycling capability (85.3 % capacitance retention after 10,000 cycles) and intrinsic tolerance to various non-stretching deformations. Moreover, the selective principles for metal ions are summarized that involved a comprehensive consideration of ionic radius, charge density and basic chemical properties. This work demonstrates an accessible and feasible construction strategy for flexible composite films and provides an alternative pathway for wearable energy storage devices.

Protonated g-C3N4/oxygen-doped g-C3N4 S-scheme homojunction fabricated by electrostatic self-assembly for photocatalytic hydrogen evolution and tetracycline hydrochloride degradation

S-scheme photocatalytic systems with high redox ability and separation efficiency of photoexcited charge carriers supply considerable prospects for environmental optimization and sustainable energy development. However, coupling well-suited reduction and oxidation components for target reactions remains a challenge worth exploring. Herein, an efficient S-scheme system for H2 generation and tetracycline hydrochloride (TCH) photodegradation based on protonated g-C3N4 (PCN) coupling with oxygen-doped g-C3N4 (OCN) is fabricated via a facile electrostatic self-assembly strategy. Intimate interfacial interactions originating from the ultrathin nanostructure and staggered energy band arrangement for the S-scheme charge transfer pathway provide compelling advantages for the highly efficient separation of photoinduced electron-hole pairs in the as-designed PCN/OCN homojunction. The in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) techniques and electron paramagnetic resonance (EPR) measurements are applied to confirm the successful construction and the validity of the S-scheme charge transfer pathway. The obtained PCN/OCN composites with optimal ratio achieve a decent H2 generation rate of 6184.7 μmol g−1 h−1 outpacing the single PCN by approximately 4.8-fold, and 90.5 % TCH photodegradation efficiency is also realized within 90 min. This work provides a delicate fresh round of elevation for the exploration of an effective photocatalytic system.

Facile self-assembly fabrication of anticorrosive imine-based composite material for excellent protective coatings

Designing suitable additive materials for high-performance anti-corrosion coatings continues to be a formidable obstacle. Although imine molecules are a promising family of organic compounds due to the π-conjugated aromatic structure containing N heteroatoms, their research as the anticorrosive additives is still in its early stages. Herein, we have prepared a rod-like imine molecule, Hexaazatrinaphthalene (HATN), which was further assembled with reduced graphene oxide (rGO) to obtain a novel HATN/rGO composite via a facile electrostatic self-assembly. As such, the HATN/rGO composite as additive material was incorporated into epoxy resin to develop a corrosion-resistant HATN/rGO epoxy coating, showing exceptional passive and active anti-corrosion properties with a low corrosion rate of 5.75 × 10−6 mm a−1 and a high corrosion inhibition efficiency of 99.83 %. Remarkably, the resistance at 0.01 Hz value of HATN/rGO epoxy coating is superior to those of rGO-based epoxy coatings previously reported. Scanning vibrating electrode technique (SVET) and salt spray measurements further demonstrate long-term performance of the HATN/rGO epoxy coating with excellent corrosion resistance. Additionally, theoretical calculation proves that the obvious electron transfer from rGO to HATN molecule promotes charge-transfer capability and electrochemical activity of the HATN/rGO composite, suggesting its great potential as the additive material for high-performance corrosion protection.

Clay-based 1D-2D halloysite&g-C3N4 nanostructured meat floss for photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) has drawn extensive attention with some features including visible-light response as non-metallic semiconductor, low cost in raw material and green pollution-free for environment, but suffers from some issues such as fast charge carriers’ recombination, easy aggregation, etc. In this work, the 1D-2D HNTs&g–C3N4–X binary materials similar to meat floss pattern in a series of halloysite loading amounts are designed via a facile electrostatic self-assembly strategy with debris g-C3N4 after cell pulverizing treatment and HNTs that outwardly modified by cetyltrimethylammonium bromide (CTAB) as the building blocks. The halloysite-mediated satellite-core material displays a photocatalytic of H2 evolution performance with the highest evolution rate of 137.0 μmol g−1 h−1 in visible light condition with no co-catalysts, and is ∼3.4 times that of bulk g-C3N4, mainly benefiting from the reduced nanometer size of debris g-C3N4 and enhanced interface dispersion ability by HNTs, resulting in ameliorative separation efficiency of photogenerated charge carriers. This research conclusively provides the new perspective towards the performance enhancement of water splitting of g-C3N4 in raw clay mineral modification mode and broadens the applications of mineral-based composite in the renewable energy utilization field.

Toward function starch nanogels by self-assembly of polysaccharide and protein: From synthesis to potential for polyphenol delivery

Nanogels formed by self-assembly of natural proteins and polysaccharides have attracted great interest as potential carriers of bioactive molecules. Herein, we reported that carboxymethyl starch-lysozyme nanogels (CMS-Ly NGs) were prepared using carboxymethyl starch and lysozyme by green and facile electrostatic self-assembly, and the nanogels served as epigallocatechin gallate (EGCG) delivery systems. The dimensions and structure of the prepared starch-based nanogels (i.e., CMS-Ly NGs) were characterized by dynamic light scattering (DLS), ζ-potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermal gravimetric analyzer (TGA). FT-IR and 1H NMR spectra together confirmed the formation of CMS; FT-IR spectra confirmed the formation of CMS-Ly NGs; XRD spectra confirmed the disruption of the crystal structure of lysozyme after electrostatic self-assembly with CMS, and further confirmed the formation of nanogels. TGA demonstrated the thermal stability of nanogels. More importantly, the nanogels showed a high EGCG encapsulation rate of 80.0 ± 1.4 %. The CMS-Ly NGs encapsulated with EGCG exhibited regular spherical structure and stable particle size. Under the simulated gastrointestinal environmental conditions, CMS-Ly NGs encapsulated with EGCG showed the controlled release potential, which increased its utilization. Additionally, anthocyanins can also be encapsulated in CMS-Ly NGs and showed slow-release properties during gastrointestinal digestion in the same way. Cytotoxicity assay also demonstrated good biocompatibility between CMS-Ly NGs and CMS-Ly NGs encapsulated with EGCG. The findings of this research suggested the potential application of protein and polysaccharides-based nanogels in the delivery system of bioactive compounds.

Efficient photocatalytic tetracycline elimination over Z-scheme g-C3N4/Bi5O7I heterojunction under sunshine light: Performance, mechanism, DFT calculation and pathway

A series of Z-scheme heterojunction g-C3N4/Bi5O7I composites were fabricated via a facile electrostatic self-assembly procedure. The optimum 15%-g-C3N4/Bi5O7I displayed good degradation efficiency toward tetracycline (TC) under visible light irradiation. The improvement of photocatalytic efficiency was mainly attributed to the generation of photo-induced h+ and O2•− radical. The migration route of photo-induced h+ and e− between g-C3N4 and Bi5O7I was investigated by XPS analysis, EPR test, photocatalytic mechanism and DFT calculations. The degradation pathways and the toxicological simulation of TC were evaluated. It was revealed that the intermediates produced during degradation process exhibited lower toxicity than the pristine TC. In addition, 15%-g-C3N4/Bi5O7I exhibited good stability and reusability. Considering its potentials in practical application, 15%-g-C3N4/Bi5O7I displayed high photocatalytic efficiency under natural sunlight irradiation. In all, this work offered a deep insight into the photocatalytic mechanism of tetracycline degradation over bismuth-rich bismuth oxyhalide/g-C3N4 heterojunction photocatalysts.

Coupled internal electric field with hydrogen release kinetics for promoted photocatalytic hydrogen production through employing carbon coated transition metal as co-catalyst.

The ideal solution to the energy shortage problem is to split water into hydrogen (H2) utilizing solar-driven semiconductor photocatalytic technology. Nevertheless, severe carrier recombination is the major cause of decreased activity over photocatalysts. Construction of internal electric field (IEF) by coupling semiconductor with metal co-catalyst can effectively promote carrier separation. Herein, Co@C with the Co encapsulated in the C layer as a co-catalyst anchored on the surface of ZnIn2S4 nanosheets via a facile electrostatic self-assembly strategy, achieving outstanding photocatalytic water splitting into H2 under simulated solar irradiation (AM 1.5G) with the production rate of 18.1mmolh-1 g-1, which is 109.7 times higher than that of bare ZIS without assisted of Pt. Enhancement of photocatalytic H2 evolution activity of Co@C/ZIS is mainly attributed to the construction of giant IEF (4.6-fold higher than ZIS) and suitable environment for hydrogen adsorption and desorption (ΔGH* ∼ 0), which endows the following several advantages: (i) accelerating the migration and separation of photo-generated charges; (ii) improving the hydrogen release kinetics. Our work not only provides a design idea for facile preparation of a high-efficient composite photocatalyst, but also expands the application range of transition metal@carbon as a co-catalyst in energy photocatalysis.

Steering bi-directional charge transfer via non-conjugated insulating polymer

Exquisite tuning of spatial charge transfer and separation has been an enduringly core issue in heterogeneous photocatalysis. Nevertheless, precise modulation of directional charge transfer to the ideal catalytically active sites remains challenging owing to rapid recombination rate of photoinduced charge carriers and sluggish charge transfer kinetics. Herein, bi-directional spatially separated electron and hole transport channels were simultaneously constructed over transition metal chalcogenides (TMCs)-based heterostructures via an efficient and facile electrostatic self-assembly strategy. Tailor-made positively charged non-conjugated polymer of branched polyethyleneimine (BPEI) and negatively charged metal nanocrystals (NCs) building blocks were controllably anchored on the TMCs substrate. We found that electrons photoexcited over TMCs substrate can migrate spontaneously, smoothly and unidirectionally to the tightly integrated neighboring metal NCs, wherein metal NCs function as Schottky-type electron-trapping reservoirs and the ultra-thin intermediate BPEI layer serves as a directional hole transport mediator, thus synergistically contributing to the significantly enhanced charge separation and prolonged charge lifetime. Benefiting from these merits, such self-assembled TMC@BPEI/metal heterostructure exhibits the markedly enhanced photoreduction catalysis toward photocatalytic hydrogen generation and anaerobic selective reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would provide inspiring idea for fine modulation of charge separation and transfer toward solar-to-chemical energy conversion.

Constructing titanium carbide MXene/reduced graphene oxide superlattice heterostructure via electrostatic self-assembly for high-performance capacitive deionization

Capacitive deionization has attracted wide concern on accountof its high energy efficiency, low manufacturing cost and environmental friendliness. Nevertheless, the development of capacitive deionization is still impeded because of the scarcity of suitable electrode materials with superior performance. Herein, we successfully prepared the two-dimensional (2D) titanium carbide (Ti3C2Tx) MXene/ reduced graphene oxide (rGO) superlattice heterostructure by a facile electrostatic self-assembly strategy and systematically investigated its performance as capacitive deionized electrode materials. The unique 2D/2D superlattice heterostructure not only effectively alleviates the self-stacking problem of Ti3C2Tx MXene nanosheets, but also endows the heterostructure with superior conductivity and fast ion diffusion rate. As a result, the MXene/rGO superlattice heterostructure exhibits an outstanding salt (Na+) adsorption capacity (48 mg g−1) at 1.2 V significantly superior to pristine Ti3C2Tx MXene nanosheets, along with outstanding long-term cycling performance. Furthermore, the mechanism involved was elucidated through comprehensive characterizations. Therefore, this study offers a new pathway for designing high-performance electrode materials for capacitive deionization.

Simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde by a noble-metal-free photocatalyst VC/CdS nanowires

In this work we used CdS NWs (nanowires) with vanadium carbide (VC) attached via facile electrostatic self-assembly and calcination method. The results showed that compared to pristine CdS NWs, the photocatalytic activity of CdS NWs loaded with the particular amount of VC was dramatically enhanced. Among them, the VC/CS-15 indicated the highest enhancement for simultaneous production of H2 with selective oxidation of benzyl alcohol (BO) into benzaldehyde (BD). The highest hydrogen evolution rate of 20.5 mmol g–1 h–1 was obtained with more than 99% selectivity for BD production under visible light (λ > 420 nm) irradiation for 2 h, which was almost 661 times higher than the pristine CdS NWs. This enhancement of photocatalytic activity is due to the VC, which provides a favorable attraction for BO by lowering the zeta potential, along with the active site for hydrogen production, and retard the recombination of electron-hole pairs by increasing the conductivity of the photocatalyst. Moreover, the apparent quantum efficiency (AQE) of VC/CS-15 for BD and H2 production at monochromatic 420 nm is about 7.5%. At the end of the hydrogen evolution test, the selective oxidation with more than 99% selectivity was obtained. It hopes this work will prove its future significance and move scientific community toward a more economical way for achieving the commercialization of H2 by photocatalysis.

Nanoscale Assembly of CdS/BiVO4 Hybrids for Coupling Selective Fine Chemical Synthesis and Hydrogen Production under Visible Light.

Simultaneously utilizing photogenerated electrons and holes in one photocatalytic system to synthesize value-added chemicals and clean hydrogen (H2) energy meets the development requirements of green chemistry. Herein, we report a binary material of CdS/BiVO4 combining one-dimensional (1D) CdS nanorods (NRs) with two-dimensional (2D) BiVO4 nanosheets (NSs) constructed through a facile electrostatic self-assembly procedure for the selectively photocatalytic oxidation of aromatic alcohols integrated with H2 production, which exhibits significantly enhanced photocatalytic performance. Within 2 h, the conversion of aromatic alcohols over CdS/BiVO4-25 was approximately 9-fold and 40-fold higher than that over pure CdS and BiVO4, respectively. The remarkably improved photoactivity of CdS/BiVO4 hybrids is mainly ascribed to the Z-scheme charge separation mechanism in the 1D/2D heterostructure derived from the interface contact between CdS and BiVO4, which not only facilitates the separation and transfer of charge carriers, but also maintains the strong reducibility of photogenerated electrons and strong oxidizability of photogenerated holes. It is anticipated that this work will further stimulate interest in the rational design of 1D/2D Z-scheme heterostructure photocatalysts for the selective fine chemical synthesis integrated with H2 evolution.

Efficient Visible-Light-Driven Photocatalytic Hydrogen Generation over 2D/2D Co-ZIF-9/Ti3 C2 Hybrids.

Exploring precious-metal-free catalysts for efficient photocatalytic H2 evolution is highly desirable but still challenging. Herein, a novel 2D/2D Co-ZIF-9/Ti3 C2 composite was fabricated by a facile electrostatic self-assembly strategy. Owing to higher flux of photogenerated electron-holes and lower rate of recombination, the resultant composite exhibited better photocatalytic H2 evolution compared to Co-ZIF-9. When the content of Ti3 C2 was 2.5 wt %, a maximum photocatalytic H2 -generation rate of 3538.5 μmol g-1 ⋅ h-1 was achieved, which is 9.6 times that of bare Co-ZIF-9. Moreover, the Co-ZIF-9/Ti3 C2 composite displayed high photocatalytic stability. This study demonstrated for the first time the great potential of Co-ZIF-9/Ti3 C2 as a noble-metal-free catalyst for photocatalytic H2 generation.

Self-assembled, highly-lithiophilic and well-aligned biomass engineered MXene paper enables dendrite-free lithium metal anode in carbonate-based electrolyte

Lithium metal anode is the ideal candidate for high-energy–density rechargeable batteries. However, uncontrolled dendrite growth hampers its commercialization. Herein, a dendrite-free composite Li metal anode is realized by a flexible, freestanding, well-aligned and highly-lithiophilic MXene paper designed by a facile electrostatic self-assembly of the exfoliated MXene nanosheets and natural polysaccharide-chitosan (MX@CS). The MX@CS paper gets a well-aligned layered-3D structure with a micro-crumpled surface that can effectively decrease the local current density, guide even Li plating and suppress dendritic Li growth. More importantly, surface-adsorbed chitosan endows enhanced lithiophilicity for MXene substrate and thus reduces the Li nucleation overpotential, which is confirmed by the density functional theory calculations. Abundant lithiophilic groups on MX@CS surface provide high-concentration Li+ anchoring site promoting Li nucleation and laterally inducing uniform Li deposition, which effectively avoids the formation of dendritic Li. As a result, the MX@CS-Li anode with a dendrite-free Li morphology shows a significantly improved cycling life in commercial carbonate-based electrolyte. When coupled with LiNi0.8Co0.1Mn0.1O2 cathode, the full cell exhibits a low capacity decay and steady ultrahigh Coulombic efficiency of 99.6% at a current density of 5C. These findings develop a new approach for designing high-performance metal-based rechargeable batteries.

Self-template-oriented synthesis of lead-free perovskite Cs3Bi2I9 nanosheets for boosting photocatalysis of CO2 reduction over Z-scheme heterojunction Cs3Bi2I9/CeO2

Lead halide perovskite (LHP) nanocrystals have been intensely studied as photocatalysts for artificial photosynthesis in recent years. However, the toxicity of lead in LHP seriously limits their potential for widespread applications. Herein, we first present the synthesis of 2D lead-free halide perovskite (Cs3Bi2I9) nanosheets with self-template-oriented method, in which BiOI/Bi2O2.7 nanosheets were used as the template and Bi ion source simultaneously. Through facile electrostatic self-assembly strategy, a Z-scheme heterojunction composed of Cs3Bi2I9 nanosheets and CeO2 nanosheets (Cs3Bi2I9/CeO2-3:1) was constructed as photocatalyst for the photo-reduction of CO2 coupled with the oxidation of H2O. Due to the matching energy levels and the close interfacial contact between Cs3Bi2I9 and CeO2 nanosheets, the separation efficiency of the photogenerated carriers in Cs3Bi2I9/CeO2-3:1 composite was significantly improved. Consequently, the environment-friendly halide perovskite heterojunction Cs3Bi2I9/CeO2-3:1 presents impressive photocatalytic activity for the reduction of CO2 to CH4 and CO with an electron consumption yield of 877.04 μmol g−1, which is over 7 and 15 times higher than those of pristine Cs3Bi2I9 and CeO2 nanosheets, exceeding the yield of other reported bismuth-based perovskite for photocatalytic CO2 reduction.

Electrostatic self-assembly of 2-dimensional MXene-wrapped sulfur composites for enhancing cycle performance of lithium–sulfur batteries

For lithium–sulfur (Li–S) batteries to be used in practical applications, the low conductivity of elemental sulfur and the shuttle phenomenon need to be overcome together with the preparation of cathode material of a high sulfur content. Herein, we report a two-dimensional (2D) delaminated MXene-wrapped sulfur composite (S@d-MXene) synthesized via facile electrostatic self-assembly. The ultrathin and flexible 2D MXene wrapping of sulfur particles provides a pathway for lithium-ion transport and electron transfer while suppressing the shuttle phenomenon. In addition, the gap between sulfur particle and the d-MXene sheets wrapping its surface provides a buffering space for the volume expansion of the sulfur particle. The Li–S battery with a high sulfur content of 83.8% in S@d-MXene composite provides a capacity of ∼506 mAh g−1 after 500 cycles at a current density of 1C, with a Coulombic efficiency of 99% and an extremely low capacity decay rate (0.047% per cycle).

Constructing electrostatic self-assembled ultrathin porous red 2D g-C3N4/Fe2N Schottky catalyst for high-efficiency tetracycline removal in photo-Fenton-like processes

The traditional heterogeneous photo-Fenton reaction was mainly restricted by the fewer surface-active sites, low Fe3+/Fe2+ transformation and H2O2 activation efficiency of catalyst. This work designed and fabricated the efficient photo-Fenton Schottky catalysts via a facile electrostatic self-assembly of metallic Fe2N nanoparticles scattering on the surface of red g-C3N4 (ultrathin porous oxygen-doped 2D g-C3N4 nanosheets). The porous morphology and exceptional electrical structure of red g-C3N4 endowed more active sites and facilitated the photoexcited charge separation. Benefitting from the Schottky effect and unique dimensional coupling structure, the strong visible light absorption and fast spatial charge transfer were realized in the Schottky junction system. More strikingly, Fe2N as an efficient co-catalyst was in favor of the trap and export of e-, leading to the Fe3+/Fe2+ transformation and H2O2 activation during the photo-Fenton process. Accordingly, the as-prepared catalysts revealed outstanding activity in photo-Fenton like degradation of tetracycline (TC) although under 5 W white LED light irradiation. Furthermore, the reasonable degradation pathway of TC and corresponding toxicity of the intermediates, as well as the photo-Fenton catalytic mechanism were interpreted and discussed in detail. This study would be a great aid in the development of various Schottky catalysts for heterogeneous photo-Fenton-based environmental remediation systems.

Rationally constructing of a novel composite photocatalyst with multi charge transfer channels for highly efficient sulfamethoxazole elimination: Mechanism, degradation pathway and DFT calculation

Rational design of highly efficient multi-heterojunction photocatalyst with separated charge transfer channels still remains a challenge. Herein, a novel La2Ti2O7/g-C3N4/AgI photocatalyst is constructed via a facile electrostatic self-assembly plus selective deposition–precipitation method. The results demonstrate that the spatially isolated La2Ti2O7 and AgI are both decorated tightly on g-C3N4 nanosheets and form separated heterojunctions, which provide much more separated charge transfer channels and surface reaction sites. Therefore, the samples exhibit remarkably boosted photodegradation performance for sulfamethoxazole (SMZ). DFT results indicate that the atoms with the most positive and negative value of condensed dual descriptors (CDD) are the mostly vulnerable to reactive species. Aromatic amine oxidation, the cleavage of sulfonamide bond and hydroxylation of aromatic rings are mainly SMZ degradation pathways. This study provides a new insight for the guideline of rational design/development of new multicomponent photocatalysts for potential application on treatment of emerging pollutants in waters.

Core-satellite metal-organic framework@upconversion nanoparticle superstructures via electrostatic self-assembly for efficient photodynamic theranostics

The nanoplatforms based on upconversion nanoparticles (UCNPs) have shown great promise in amplified photodynamic therapy (PDT) triggered by near-infrared (NIR) light. However, their practical in vivo applications are hindered by the overheating effect of 980 nm excitation and low utilization of upconversion luminescence (UCL) by photosensitizers. To solve these defects, core-satellite metal-organic framework@UCNP superstructures, composed of a single metal-organic framework (MOF) NP as the core and Nd3+-sensitized UCNPs as the satellites, are designed and synthesized via a facile electrostatic self-assembly strategy. The superstructures realize a high co-loading capacity of chlorin e6 (Ce6) and rose bengal (RB) benefitted from the highly porous nature of MOF NPs, showing a strong spectral overlap between maximum absorption of photosensitizers and emission of UCNPs. The in vitro and in vivo experiments demonstrate that the dual-photosensitizer superstructures have trimodal (magnetic resonance (MR)/UCL/fluorescence (FL)) imaging functions and excellent antitumor effectiveness of PDT at 808 nm NIR light excitation, avoiding the laser irradiation-induced overheating issue. This study provides new insights for the development of highly efficient PDT nanodrugs toward precision theranostics.

L-serine-assisted synthesis of Fe3O4 impregnated N-doped RGO composites via a facile electrostatic self-assembly for synergistic adsorption of Rhodamine B

In this work, Fe3O4 nanoparticles impregnated N-doped RGO (Fe3O4-N-RGO) nanocomposite was synthesized through one-pot electrostatic self-assembly of magnetite nanoparticles (Fe3O4 NPs) on N-doped RGO sheet in the presence of L-serine (L-Ser) as a surface functionalizing and reducing agent. The surface property, structure, morphology, and magnetic properties of as-prepared Fe3O4-N-RGO nanocomposite were characterized by FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), and electron paramagnetic resonance spectroscopy (EPRS). The XRD results were indicated the formation of high crystalline spinel type Fe3O4 NPs. The Fe3O4 nanoparticles with average sizes of 12 nm were formed uniformly on reduced graphene sheets. The Fe3O4-N-RGO nanocomposite was used as an adsorbent to remove Rhodamine B dye from aqueous solution. The nanocomposite shows excellent ability to adsorb organic pollutants and can be easily manipulated in a magnetic field for separation. The results suggest that Fe3O4-N-RGO nanocomposite has great potential for efficient removal of organic dyes pollutants from aqueous solution.

Core/Shell Structure of Mesoporous Carbon Spheres and g-C3N4 for Acid Red 18 Decolorization

Spherical photocatalyst based on ordered mesoporous carbon and graphitic carbon nitride with core/shell structure (CS/GCN) was successfully synthesized via facile electrostatic self-assembly strategy. The photocatalytic properties of the hybrid were evaluated by the decomposition of Acid Red 18 under simulated solar light irradiation in comparison to the bulk graphitic carbon nitride (GCN). The results clearly revealed that coupling of carbon nitride with mesoporous carbon allows the catalyst to form with superior photocatalytic performance. The photoactivity of CS/GCN was over nine times higher than that of pristine GCN. Introducing mesoporous carbon into GCN induced higher surface area of the heterojunction and also facilitated the contact surface between the two phases. The synergistic effect between those two components enhanced the visible light-harvesting efficiency and improved photoinduced charge carrier generation, and consequently their proper separation. The electrochemical behavior of the obtained composite was also evaluated by electrochemical impedance, transient photocurrent response and linear sweep potentiometry measurements. The results confirmed that transport and separation of charge carriers in the hybrid was enhanced in comparison to the reference bulk graphitic carbon nitride. Detailed electrochemical, photoluminescence and radical scavenger tests enabled determination of the possible mechanism of photocatalytic process. This work presents new insights to design a core/shell hybrid through the simple preparation process, which can be successfully used as an efficient photocatalyst for the treatment of wastewater containing dyes under solar light irradiation.