Graphene oxide–metal oxide nanocomposites: fabrication,characterization and removal of cationic rhodamine B dye

The fabrication and characterization of graphene oxide (GO) nanosheets and their reaction with Fe₃O₄ and ZrO₂ metal oxides to form two nanocomposites, namely graphene oxide–iron oxide (GO–Fe₃O₄) and graphene oxide–iron oxide–zirconium oxide (GO–Fe₃O₄@ZrO₂), have been examined. The fabricated nanocomposites were examined using different techniques, e.g.transmission electron microscopy, X-ray diffraction, zeta potential measurement and Fourier transform infrared spectroscopy. Compared to GO, the newly fabricated GO–Fe₃O₄ and GO–Fe₃O₄@ZrO₂ nanocomposites have the advantage of smaller band gaps, which result in increased adsorption capacity and photocatalytic effects. The results also showed the great effect of the examined GO–metal oxide nanocomposites on the decomposition of cationic rhodamine B dye, as indicated by steady-state absorption and fluorescence, time correlated single photon counting and nanosecond laser photolysis techniques. The antibacterial activity of the fabricated GO and GO–metal oxides has been studied against Gram-positive and Gram-negative bacteria.

The fabrication and characterization of graphene oxide–iron oxide and graphene oxide–iron oxide–zirconium oxide nanocomposites have been reported. The decomposition of cationic rhodamine B dye by both nanocomposites has been examined.     

Tribological behavior of in situ fabricated graphene–nickel matrix composites

Graphene–nickel (G–Ni) composites were in situ fabricated by a powder metallurgy method. The effects of graphene content on the tribological behavior of G–Ni composites were investigated. The tribochemistry and structural evolution of graphene were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to understand the lubricating role of graphene in the G–Ni composite. The results show that graphene protects the nickel matrix from severe oxidation at the expense of its oxidation during sliding friction. Graphene on the friction interface transforms from a structure with less defects to a disordered amorphous structure. Polymeric segments are also generated by the tribochemical reactions of graphene. The formation of the tribofilms containing amorphous carbon and polymers is responsible for the self-lubricating behavior of the G–Ni composites.

Graphene protects nickel from severe oxidation and forms carbon-rich tribofilms containing disordered amorphous carbon and ordered polymers by tribo-chemical reactions.     

A facile and general approach for the direct fabrication of N-rGO–metal(metal oxides)–Pt composites as electrocatalyst for oxygen reduction reactions

Nitrogen-doped reduced graphene oxide–metal(metal oxides) nanoparticle (N-rGO–M(MO) NPs, M = Fe, MO: M = Co, Mn) composites were prepared through a facile and general method at high temperature (800 °C). M(MO) were well-dispersed and tightly anchored on graphene sheets, which were doped with nitrogen simultaneously and further loaded with Pt nanoparticles. Those results showed a more positive onset potential, higher cathodic density, and higher electron transfer number for the ORR in alkaline media. Furthermore, N-rGO–metal(metal oxides)–Pt (N-rGO–M(MO)–Pt) nanoparticles show better durability than the commercial Pt/C catalyst, and can be used as promising potential materials in practical applications.

We developed a facile, yet general approach to prepare N-rGO–M(MO)–Pt (M = Co, Fe and Mn) composites, which showed excellent electrocatalytic activity for the ORR in alkaline electrolytes.     

Generalized nano-thermodynamic model for capturing size-dependent surface segregation in multi-metal alloy nanoparticles

Multi-metal alloy nanoparticles (NPs) offer new avenues for exploration and design of nanoscale-properties, e.g., catalytic, electronic and optical properties, by virtue of their tunable composition. A method that can aid such exploration by accurately predicting the size-, shape- and composition-dependent elemental distribution associated with nanomaterials is crucially missing. A nano-thermodynamic model based on distribution coefficients Δ is introduced to fill this gap. Δ is employed to predict surface segregation in NPs as a function of the NP size and composition. Interestingly, we find Δ to be independent of size for NPs beyond 2 nm. This key finding motivates the construction of thermodynamic tables for distribution coefficients using segregation observed with one or more NP sizes. The tables can enable accurate prediction of phase diagrams for nanomaterials across a wide-range of sizes. Key concepts of this new theory are demonstrated with Au–Pt–Pd, Ag–Au–Pd and Ni–Pt–Pd, which are found to exhibit complex size-dependent segregation behavior for 2–6 nm NPs and relatively weaker size-dependence beyond 6 nm. Numerically well-converged values of Δ are calculated for small NPs using Monte Carlo simulations in the canonical ensemble. Simulations are based on an embedded atom method (EAM) potential for metal alloys.

Nano-thermodynamic model captures thermodynamic preference of metal species for different regions of a nanoparticle while accounting for size effects.     

Synthesis and characterization of TiO2/graphene oxide nanocomposites for photoreduction of heavy metal ions in reverse osmosis concentrate

In this study, graphene oxide (GO), titanium dioxide (TiO₂) and TiO₂/GO nanocomposites were synthesized as the catalysts for photoreduction of endocrine disrupting heavy metal ions in reverse osmosis concentrates (ROC). The morphology, structure and chemical composition of these catalysts were characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Brunauer–Emmett–Teller analysis, Barrett–Joyner–Halenda, Fourier transform infrared spectroscopy and Raman spectroscopy. The photocatalytic experiments showed that TiO₂/GO nanocomposites exhibit a higher photoreduction performance than pure TiO₂ and GO. Under the optimal conditions, the removal rates of Cd²⁺ and Pb²⁺ can reach 66.32 and 88.96%, respectively, confirming the effectiveness of photoreduction to reduce the endocrine disrupting heavy metal ions in ROC resulted from the combined adsorption–reduction with TiO₂/GO nanocomposites.

TiO₂/GO nanocomposites were synthesized successfully and exhibited an excellent ability to reduce heavy metal ions in reverse osmosis concentrate.     

Vitamin C assisted synthesis of rGO–Ag/PANI nanocomposites for improved photocatalytic degradation of pharmaceutical wastes

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol. The structural, morphological, and light absorption properties of the as-synthesized rGO–Ag/PANI were characterized by UV-Visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Paracetamol was taken as a model water pollutant to investigate the photocatalytic degradation efficiency of the rGO–PANI/Ag nanocomposites under visible light radiation. The result shows the degradation of paracetamol to be 99.6% in the acidic medium (pH 5) and 75.76% in the basic medium (pH 9), respectively. The enhanced degradation efficiency is attributed to the synergetic effect of rGO, PANI, and Ag NPs in the nanocomposites. This synergy of the rGO–Ag/PANI is explained by the strong adsorption efficiency, charge separation, and light absorption in the visible region.

A highly efficient visible light active polyaniline (PANI)/Ag composites grafted reduced graphene oxide (rGO–Ag/PANI) was prepared for the efficient photocatalytic degradation of paracetamol.     

A facile synthesis of high entropy alloy nanoparticle–activated carbon nanocomposites for synergetic degradation of methylene blue

Nanocomposites of CoCrFeMnNi high entropy alloy nanoparticle–activated carbon (HEA NPs–AC) were prepared by a facile and controllable impregnation–adsorption method. The HEA NPs–AC showed excellent catalytic performance in the degradation of methylene blue (MB) without any peroxide addition. Besides, their reaction rate is also competitive among single-element and other catalysts. The outstanding efficiency is attributed to the coupling effects of the solid-solution structure of HEA NPs, and the large specific surface area and substantial reaction channels of AC. Moreover, the HEA NPs embedded in distinctive porous architectures accelerate the electron transfer and the mass transport as nanoscale galvanic cells in active bond breaking of MB. The nanocomposites of HEA NPs–AC are distinguished by containing non-noble metals and having high catalytic performance due to the synergetic degradation, providing a better alternative for efficient metal catalysis.

CoCrFeMnNi HEA NPs–AC were synthesized facilely with FCC solid solution phase and outstanding catalytic performance. The time required to reduce MB concentration can be as short as 12 min with the k_obs of 0.191 min⁻¹ for the 10 wt% catalyst.     

Large-scale production of CdO/Cd(OH)2 nanocomposites for non-enzyme sensing and supercapacitor applications

Recent advancements in electrode design are substantially linked to state-of-the-art nanomaterial fabrications. Herein, we report a simple one-pot hydrothermal synthesis of Cd(OH)₂ with a platelet-like morphology, which was subsequently annealed at relatively high temperatures to produce a CdO/Cd(OH)₂ nanocomposite for the first time. It was found that the control of thermal treatment allowed tunable charge transport across the nanometre scale due to the presence of CdO and Cd(OH)₂ mixed nanocrystals. The CdO/Cd(OH)₂ nanocrystals offer interesting prospects for the electrocatalytic oxidation of nitrite ions and for supercapacitor applications. The CdO/Cd(OH)₂ nanocomposite was blended with a trace amount of gold NPs for enhancing the electrochemical conductivity and electrocatalytic capability for nitrite oxidation with a sensitivity of 32.9 μA mM⁻¹. It afforded a promising electrocatalyst in a wide concentration range up to 10 mM with a low detection limit of 0.87 μM. Furthermore, the CdO/Cd(OH)₂ nanocomposite electrode was showed to be a highly active and stable supercapacitor, achieving a high specific capacitance in an alkaline medium of about 145 F g⁻¹ at a discharge current of 2.0 A g⁻¹. These results have revealed that the presence of mixed oxide/hydroxide nanocrystals in nanoscale dimensions will be very interesting for various electrochemical applications and provide for a new class of nanodevices based on electrochemistry with unique capabilities.

A simple fabrication of CdO/Cd(OH)₂ nanocomposites was developed and explored for electrochemical-based devices. The nanocomposite is shown to be a sensitive electrode material for nitrite determination in water samples as well as a promising supercapacitor.     

Graphene oxide decorated with zinc oxide nanoflower,silver and titanium dioxide nanoparticles: fabrication,characterization, DNA interaction,and antibacterial activity

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined. The fabricated nanocomposites were characterized by various techniques including X-ray diffraction, ultraviolet-visible light absorption and fluorescence spectroscopy, Brunauer–Emmett–Teller theory analysis, Fourier transform infrared, and scanning electron microscopy. The antibacterial activity of the GO–metal oxide nanocomposites against two Gram-positive and two Gram-negative bacteria was examined by using the standard counting plate methodology. The results showed that the fabricated nanocomposites on the surface of GO could inhibit the growth of microbial adhered cells, and consequently prevent the process of biofilm formation in food packaging and medical devices. To confirm the antibacterial activity of the examined GO-nanocomposites, we examined their interactions with bovine serum albumin (BSA) and circulating tumor DNA (ctDNA) by steady-state fluorescence spectroscopy. Upon addition of different amounts of fabricated GO-nanocomposites, the fluorescence intensities of the singlet states of BSA and ctDNA were considerably quenched. The higher quenching was observed in the case of GO–Ag–TiO₂@ZnO nanocomposite compared with other control composites.

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined.     

Preparation of cobalt sulfide@reduced graphene oxide nanocomposites with outstanding electrochemical behavior for lithium-ion batteries

Cobalt sulfide@reduced graphene oxide composites were prepared through a simple solvothermal method. The cobalt sulfide@reduced graphene oxide composites are composed of cobalt sulfide nanoparticles uniformly attached on both sides of reduced graphene oxide. Some favorable electrochemical performances in specific capacity, cycling performance, and rate capability are achieved using the porous nanocomposites as an anode for lithium-ion batteries. In a half-cell, it exhibits a high specific capacity of 1253.9 mA h g⁻¹ at 500 mA g⁻¹ after 100 cycles. A full cell consists of the cobalt sulfide@reduced graphene oxide nanocomposite anode and a commercial LiCoO₂ cathode, and is able to hold a high capacity of 574.7 mA h g⁻¹ at 200 mA g⁻¹ after 200 cycles. The reduced graphene oxide plays a key role in enhancing the electrical conductivity of the electrode materials; and it effectively prevents the cobalt sulfide nanoparticles from dropping off the electrode and buffers the volume variation during the discharge–charge process. The cobalt sulfide@reduced graphene oxide nanocomposites present great potential to be a promising anode material for lithium-ion batteries.

Cobalt sulfide@reduced graphene oxide nanocomposites obtained through a dipping and hydrothermal process, exhibit ascendant lithium-ion storage properties.     

Cobalt-modified palladium nanocatalyst on nitrogen-doped reduced graphene oxide for direct hydrazine fuel cell

Nitrogen-doped reduced graphene oxide-supported palladium–cobalt nanoparticles (PdCo NPs/NrGO NSs) are synthesized and used as a high-performance and low-cost anodic catalyst for direct hydrazine–hydrogen peroxide fuel cells. The SEM and TEM images of PdCo NPs/NrGO NSs show the uniform metal nanoparticle distribution on the NrGO NSs. The reduction of the oxygen functional groups and the doping of the nitrogen atoms in the GO framework are confirmed by FT-IR and XRD spectroscopic studies. The Pd catalysts modified by Co exhibit a higher catalytic activity, lower onset potential, better durability, and lower impedance values than unmodified Pd catalysts for the electro-oxidation of hydrazine. The kinetic studies show a first-order reaction with an activation energy of 12.51 kJ mol⁻¹. A direct hydrazine–hydrogen peroxide fuel cell with PdCo NPs/NrGO NSs as anode and Pt/C as cathode provides an open circuit voltage of 1.76 V and a maximum power density of 148.58 mW cm⁻² at 60 °C, indicating that the PdCo NPs/NrGO NSs are an economical, high performance and reliable anode catalyst for the direct hydrazine–hydrogen peroxide fuel cell.

The superior catalytic activity and stability of a novel anodic PdCo NPs/NrGO NSs for HzOR are confirmed by half and signal cell investigations.     

Cu nanoparticles decorated WS2 nanosheets as a lubricant additive for enhanced tribological performance

Tungsten disulfide–polydopamine–copper (WS₂–PDA–Cu) nanocomposites were first prepared by a green and effective biomimetic strategy and then used as a lubricant additive in polyalkylene glycol (PAG). The biomimetic strategy is inspired by the adhesive proteins in mussels. WS₂ nanosheets were decorated by uniformly dispersed Cu nanoparticles (Cu NPs). The WS₂–PDA–Cu nanocomposites with good dispersion stability, showed better friction reducing and anti-wear properties than WS₂, Cu NPs and WS₂–Cu dispersed in PAG base oil. The average friction coefficient and wear volume were reduced by 33.56% and 97.95%, respectively, at 150 °C under a load of 100 N for the optimal concentration of 0.9 wt%. The lubrication mechanism was discussed.

Tungsten disulfide–polydopamine–copper (WS₂–PDA–Cu) nanocomposites were first prepared by a green and effective biomimetic strategy and then used as a lubricant additive in polyalkylene glycol (PAG).     

Thermal property improvement of polytetrafluoroethylene nanocomposites with graphene nanoplatelets

Thermal properties including the crystallization behavior, thermal stability and thermal conductivity for a series of graphene nanoplatelet (GNP)–polytetrafluoroethylene (PTFE) nanocomposites were studied. The GNP–PTFE nanocomposites were fabricated via solvent-assisted blending followed by cold-pressing and sintering. The results indicated that the GNP–PTFE nanocomposites retained the good thermal stability of the PTFE matrix, and possessed better crystallization and much higher thermal conductivity than pure PTFE. The thermal conductivity of PTFE nanocomposites with a GNP mass fraction of 20% could reach 4.02 W (m K)⁻¹, which was increased by 1300% compared with pure PTFE. Additionally, a theoretical model was proposed to analyze the thermal conductivity of GNP–PTFE nanocomposites. It is demonstrated that adding GNPs into PTFE homogeneously can effectively improve the thermal properties of the nanocomposites.

Adding GNPs into PTFE can significantly improve the thermal properties of nanocomposites.     

Synergistic effect of graphene and silicon dioxide hybrids through hydrogen bonding self-assembly in elastomer composites

A novel graphene–silicon dioxide hybrid (HGS) was prepared by plant polyphenol-tannic acid (TA) functionalized pristine graphene (G-TA) and primary amine-containing silane coupling agent modified SiO₂ (Si–NH₂). Through strong hydrogen-bonding interaction between the phenolic hydroxyl groups on G-TA and primary amine groups on Si–NH₂, SiO₂ was uniformly loaded to the surface of graphene. Due to the synergistic dispersion effect of graphene and SiO₂, which prevents restacking and re-aggregating of both graphene and SiO₂, HGS hybrids were distributed evenly in the natural rubber (NR) matrix (HGS@NR). Simultaneously, the surface roughness of graphene after loading SiO₂ and the interfacial interaction between the HGS hybrid and NR matrix were substantially improved. Due to the good dispersion and strong interface, the overall properties of HGS@NR nanocomposites are drastically enhanced compared with those of GS@NR nanocomposites prepared by dispersing the blend of unmodified graphene and SiO₂ (GS) in NR. The HGS@NR nanocomposites possess the highest tensile strength up to 27.8 MPa at 0.5 wt% and tear strength of 60.2 MPa at 0.5 wt%. Thermal conductivities of the HGS@NR nanocomposites were found to be 1.5-fold better than that of the GS@NR nanocomposites. Also, the HGS@NR nanocomposites exhibit excellent abrasive resistant capacity that is nearly 2-fold better than that of the GS@NR nanocomposites. These results suggest that HGS has great potential in high-performance nanocomposites and a new strategy of constructing the efficient graphene–SiO₂ hybrid fillers has been established.

A novel graphene–silicon dioxide hybrid (HGS) was prepared by plant polyphenol-tannic acid (TA) functionalized pristine graphene (G-TA) and primary amine-containing silane coupling agent modified SiO₂ (Si–NH₂).     

Application of micro-impinging stream reactors in the preparation of Co and Al co-doped Ni(OH)2 nanocomposites for supercapacitors and their modification with reduced graphene oxide

A micro-impinging stream reactor (MISR) consisting of a commercial T-junction and steel capillaries, which is of intensified micromixing efficiency as compared with traditional stirred reactors (STR), was applied for the preparation of Co and Al co-doped Ni(OH)₂ nanocomposites and their modification with reduced graphene oxide (RGO). The co-precipitation preparation process was conducted under precisely controlled proportions and concentrations of reactants in the MISR. Therefore, element analysis showed a higher uniform distribution of metal ions within the nanocomposites obtained through the MISR. The structural characterization and electrochemical measurements also showed that the MISR-prepared metal-doped nanocomposites were of more uniform dispersion and superior electrochemical performance than those prepared with STR. In addition, by modifying with RGO in the MISR, the electrochemical performance of Co and Al co-doped Ni(OH)₂ nanocomposites could be further improved. The Co and Al co-doped Ni(OH)₂/RGO prepared under optimal conditions achieved an ultrahigh specific capacitance of 2389.5 F g⁻¹ at the current density of 1 A g⁻¹ and displayed an excellent cycling stability with 83.7% retention of the initial capacitance after 1000 charge/discharge cycles in 6 M KOH aqueous solution.

High performance Ni–Co–Al(OH)_n nanocomposites as supercapacitors were prepared and modified with reduced graphene oxide within a novel micro-impinging stream reactor.     

Construction of ultrathin MnO2 decorated graphene/carbon nanotube nanocomposites as efficient sulfur hosts for high-performance lithium–sulfur batteries

Lithium–sulfur batteries are attracting significant attention due to their high theoretical specific capacity and low cost. However, their applications are hindered by the poor conductivity of sulfur and capacity fading caused by the shuttle effect. Here, ultrathin manganese dioxide decorated graphene/carbon nanotube nanocomposites are designed as sulfur hosts to suppress the shuttle effect and improve the adsorption efficiency of polysulfides. The graphene/carbon nanotube hybrids, with extraordinary conductivity and large surface area, function as excellent channels for electron transfer and lithium ion diffusion. The ultrathin manganese dioxide nanosheets enable efficient chemical interaction with polysulfides and promote the redox kinetics of polysulfides. As a result, an ultrathin manganese dioxide decorated graphene/carbon nanotube sulfur composite with high sulfur content (81.8 wt%) delivers a high initial specific capacity of 1015.1 mA h g⁻¹ at a current density of 0.1C, high coulombic efficiency approaching 100% and high capacity retention of 84.1% after 100 cycles. The nanocomposites developed in this work have promising applications in high-performance lithium–sulfur batteries.

Ultrathin MnO₂ nanosheets and nano size sulfur particles distributed uniformly on the surface of G/CNT hybrids, which exhibit high rate performance and long-term cycling performance.     

Surface functionality density regulated in situ reduction of nanosilver on hierarchial wrinkled mesoporous silica nanoparticles and their antibacterial activity

Hierarchical wrinkled mesoporous silica nanoparticles (WMS NPs) bedecked with diverse functionality density of amino groups (WMSs-N2, WMSs-NN and WMSs-NNN) were first synthesized via typical Sol–Gel method, and then utilized for the in situ reduction of nanosilver with sodium borohydride. Elegantly distributed Ag NPs (ca. 7–10 nm, 3–5 nm) on WMSs-N2 and WMSs-NN without any agglomeration were obtained respectively, while Ag NPs (ca. 50 nm) dispersed on WMSs-NNN were obviously larger and slightly agglomerated. Compared to pure Ag NPs, all the obtained Ag@WMSs composites were durable and displayed much better antibacterial performance, with a minimal inhibitory concentration of 12–80 mg L⁻¹ and a minimal bactericidal concentration of 24–108 mg L⁻¹, respectively. Moreover, it was found that the functionality density of amino groups and the specific surface area of WMSs played a crucial role for the antibacterial performance of the obtained nanocomposites. Because WMSs-NN had higher specific surface area and surface amino density than WMSs-N2, the size and dispersion of Ag NPs on WMSs-NN were smaller and superior to those of Ag NPs on WMSs-N2, respectively. Accordingly, Ag@WMSs-NN displayed a better antibacterial capacity than Ag@WMSs-N2. As for Ag@WMSs-NNN, owing to the high loading content of Ag NPs, they exhibited the best antibacterial and bactericidal properties.

Nanosilver with diverse particle size was attached onto hierarchical WMS, and the resulted samples showed excellent antibacterial properties.     

Fabrication and prospective applications of graphene oxide-modified nanocomposites for wastewater remediation

Water bodies have become polluted with heavy metals and hazardous contaminants as a result of fast development. Many strategies have been devised by researchers in order to remove hazardous contaminants from the aquatic environment. Utilizing graphene oxide-based composite materials as efficient adsorbents for waste water treatment, desalination, separation, and purification is gaining attraction nowadays. Some of their defining properties are high mechanical strength, hydrophilicity, remarkable flexibility, ease of synthesis, atomic thickness, and compatibility with other materials. In water treatment, high separation performance and stable graphene-based laminar structures have been the main goals. Magnetic separation is among the methods which received a lot of attention from researchers since it has been shown to be quite effective at removing harmful pollutants from aqueous solution. Graphene oxide-modified nanocomposites have provided optimal performance in water purification. This review article focusses on the fabrication of GO, rGO and MGO nanocomposites as well as the primary characterization tools needed to assess the physiochemical and structural properties of graphene-based nanocomposites. It also discusses the approaches for exploiting graphene oxide (GO), reduced graphene (rGO), and magnetic graphene oxide (MGO) to eliminate contaminants for long-term purification of water. The potential research hurdles for using fabricated MGOs as an adsorbent to remediate water contaminants like hazardous metals, radioactive metal ions, pigments, dyes, and agricultural pollutants are also highlighted.

Synthesis and chacterization of graphene-based materials (GO, rGO, and MGO) by FT-IR, XRD, UV-VIS, SEM, and Raman spectroscopy, and their potential applications for wastewater treatment.     

Synthesis of manganese-oxide and palladium nanoparticles co-decorated polypyrrole/graphene oxide (MnO2@Pd@PPy/GO) nanocomposites for anti-cancer treatment

Design and fabrication of novel multifunctional nanomaterials as novel “theranostic nanoagents”with high efficiency and low side effects is important for cancer treatment. Herein, we synthesized manganese-oxide and palladium nanoparticle-co-decorated polypyrrole/graphene oxide (MnO₂@Pd@PPy/GO) nanocomposites, which could be used as a novel “theranostic nanoagent” for cancer treatment. Various spectroscopic and microscopic characterizations of the synthesized MnO₂@Pd@PPy/GO nanocomposites suggest that the nanocomposites are assembled sequentially by graphene oxide, polypyrrole, palladium nanoparticles and manganese-oxide nanoplates. Further research revealed that the nanocomposites had excellent photothermal conversion performance (reached near 50 °C after 10 min of irradiation), pH responsive enzymatic-like catalytic activity and enhanced magnetic resonance imaging (MRI) performance (r₁ = 7.74 mM⁻¹ s⁻¹ at pH 5.0 and glutathione (GSH)). Cell experiments also testified that combined cancer treatment (the viability of cancer cells is 30%) with photothermal therapy (PTT, the viability of cancer cells is 91% only with irradiation) and chemodynamic therapy (CDT, the viability of cancer cells is 74.7% only with nanocomposites) guided by MRI was achieved when the as-prepared nanocomposites were employed as theranostic nanoagents. This work could provide some new ideas for the controllable synthesis and application of multicomponent nanomaterials.

Manganese-oxide and palladium nanoparticle-co-decorated polypyrrole/graphene oxide (MnO₂@Pd@PPy/GO) nanoenzyme composites were synthesized, and could be as a novel “theranostic nanoagent” for cancer treatment due to excellent performance.     

Porous BMTTPA–CS–GO nanocomposite for the efficient removal of heavy metal ions from aqueous solutions

In this study, a stable, cost-effective and environmentally friendly porous 2,5-bis(methylthio)terephthalaldehyde–chitosan–grafted graphene oxide (BMTTPA–CS–GO) nanocomposite was synthesized by covalently grafting BMTTPA–CS onto the surfaces of graphene oxide and used for removing heavy metal ions from polluted water. According to well-established Hg²⁺–thioether coordination chemistry, the newly designed covalently linked stable porous BMTTPA–CS–GO nanocomposite with thioether units on the pore walls greatly increases the adsorption capacity of Hg²⁺ and does not cause secondary pollution to the environment. The results of sorption experiments and inductively coupled plasma mass spectrometry measurements demonstrate that the maximum adsorption capacity of Hg²⁺ on BMTTPA–CS–GO at pH 7 is 306.8 mg g⁻¹, indicating that BMTTPA–CS–GO has excellent adsorption performance for Hg²⁺. The experimental results show that this stable, environmentally friendly, cost-effective and excellent adsorption performance of BMTTPA–CS–GO makes it a potential nanocomposite for removing Hg²⁺ and other heavy metal ions from polluted water, and even drinking water. This study suggests that covalently linked crucial groups on the surface of carbon-based materials are essential for improving the adsorption capacity of adsorbents for heavy metal ions.

Novel porous BMTTPA–CS–GO nanocomposites are prepared by covalently grafting BMTTPA–CS onto GO surfaces, and used for efficient removal of heavy metal ions from polluted water.