High yield conversion of biowaste coffee grounds into hierarchical porous carbon for superior capacitive energy storage.

Recently great efforts have been focused on converting biowastes into high-valued carbon materials. However, it is still a great challenge to achieve high carbon yield and controllable porous distribution in both industrial and academic research. Inspired by the multi-void structure of waste coffee grounds, herein we fabricated hierarchical porous carbon via the combination of catalytic carbonization and alkali activation. The catalytic carbonization process was applied to obtain well-defined mesoporous carbon with carbon yield as high as 42.5 wt%, and subsequent alkali activation process produced hierarchical porous carbon with ultrahigh specific surface area (3549 m2 g-1) and large meso-/macropores volume (1.64 cm3 g-1). In three-electrode system, the electrode exhibited a high capacitance of 440 F g-1 at 0.5 A g-1 in 6 M KOH aqueous electrolyte, superior to that of many reported biomass-derived porous carbons. In two-electrode system, its energy density reached to 101 Wh kg-1 at the power density of 900 W kg-1 in 1-Ethyl-3-Methylimidazolium Tetrafluoroborate (EMIMBF4). This work provided a cost-effective strategy to recycle biowastes into hierarchical porous carbon with high yield for high-performance energy storage application.

Evaluation of Nanoporous Carbon Synthesized from Direct Carbonization of a Metal⁻Organic Complex as a Highly Effective Dye Adsorbent and Supercapacitor.

The synthesis of interconnected nanoporous carbon (NPC) material from direct annealing of ultra-small Al-based metal-organic complex (Al-MOC) has been demonstrated. NPC presents a large accessible area of 1,054 m²/g, through the Methylene Blue (MB) adsorption method, which is comparable to the high specific surface area (SSA) of 1,593 m²/g, through an N2 adsorption/desorption analysis. The adsorption properties and mechanisms were tested by various dye concentrations, pH, and temperature conditions. The high MB accessible area and the good electrical conductivity of the interconnected NPC, led to a large specific capacitance of 205 F/g, with a potential window from 0 to 1.2 V, in a symmetric supercapacitor, and a large energy density of 10.25 Wh/kg, in an aqueous electrolyte, suggesting a large potential in supercapacitors.

Large-scale converting waste coffee grounds into functional carbon materials as high-efficient adsorbent for organic dyes.

Functional carbon materials have been fabricated through simple and effective catalytic carbonization with waste coffee grounds (CGs) as carbon precursor and FeCl3 as catalyst. The effect of FeCl3 loading and carbonization temperature on carbon yield was investigated. The morphology and structure of as-synthesized carbons was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and nitrogen isothermal adsorption/desorption measurement, respectively. Furthermore, the carbon materials showed high efficiency for the removal of methylene blue (MB, 653.6 mg g-1), methyl orange (MO, 465.8 mg g-1) and rhodamine B (RB, 366.1 mg g-1). More importantly, the carbon was magnetic, so it can be easily separated by a magnet and reused multiple times. This work not only exploited a low-cost and large-scale preparation method to synthesize functional carbon materials from bioresources, but also provided an eco-friendly and effective adsorbent in water purification applications.

Combined photothermal and photodynamic therapy delivered by PEGylated MoS2 nanosheets.

Single- or few-layered transitional metal dichalcogenides, as a new genus of two-dimensional nanomaterials, have attracted tremendous attention in recent years, owing to their various intriguing properties. In this study, chemically exfoliated MoS2 nanosheets are modified with lipoic acid-terminated polyethylene glycol (LA-PEG), obtaining PEGylated MoS2 (MoS2-PEG) with high stability in physiological solutions and no obvious toxicity. Taking advantage of its ultra-high surface area, the obtained MoS2-PEG is able to load a photodynamic agent, chlorin e6 (Ce6), by physical adsorption. In vitro experiments reveal that Ce6 after being loaded on MoS2-PEG shows remarkably increased cellular uptake and thus significantly enhanced photodynamic therapeutic efficiency. Utilizing the strong, near-infrared (NIR) absorbance of the MoS2 nanosheets, we further demonstrate photothermally enhanced photodynamic therapy using Ce6-loaded MoS2-PEG for synergistic cancer killing, in both in vitro cellular and in vivo animal experiments. Our study presents a new type of multifunctional nanocarrier for the delivery of photodynamic therapy, which, if combined with photothermal therapy, appears to be an effective therapeutic approach for cancer treatment.

Tumor metastasis inhibition by imaging-guided photothermal therapy with single-walled carbon nanotubes.

Multi-modal imaging guided photothermal therapy with single-walled carbon nanotubes affords effective destruction of primary tumors together with cancer cells in sentinel lymph nodes. This results in remarkably prolonged mouse survival compared to mice treated by elimination of only the primary tumor by either surgery or conventional photothermal therapy.

Graphene-based nanocomposite as an effective, multifunctional, and recyclable antibacterial agent.

The development of new antibacterial agents that are highly effective are of great interest. Herein, we present a recyclable and synergistic nanocomposite by growing both iron oxide nanoparticles (IONPs) and silver nanoparticles (AgNPs) on the surface of graphene oxide (GO), obtaining GO-IONP-Ag nanocomposite as a novel multifunctional antibacterial material. Compared with AgNPs, which have been widely used as antibacterial agents, our GO-IONP-Ag shows much higher antibacterial efficiency toward both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus). Taking the advantage of its strong near-infrared (NIR) absorbance, photothermal treatment is also conducted with GO-IONP-Ag, achieving a remarkable synergistic antibacterial effect to inhibit S. aureus at a rather low concentration of this agent. Moreover, with magnetic IONPs existing in the composite, we can easily recycle GO-IONP-Ag by magnetic separation, allowing its repeated use. Given the above advantages as well as its easy preparation and cheap cost, GO-IONP-Ag developed in this work may find potential applications as a useful antibacterial agent in the areas of healthcare and environmental engineering.

Smart pH-responsive nanocarriers based on nano-graphene oxide for combined chemo- and photothermal therapy overcoming drug resistance.

A pH-responsive nanocarrier is developed by coating nanoscale graphene oxide (NGO) with dual types of polymers, polyethylene glycol (PEG) and poly(allylamine hydrochloride) (PAH), the latter of which is then modified with 2,3-dimethylmaleic anhydride (DA) to acquire pH-dependent charge reversibility. After loading with doxorubicin (DOX), a chemotherapy drug, the obtained NGO-PEG-DA/DOX complex exhibits a dual pH-responsiveness, showing markedly enhanced cellular uptake under the tumor microenvironmental pH, and accelerated DOX release under a further lowered pH inside cell lysosomes. Combining such a unique behavior with subsequently slow efflux of DOX, NGO-PEG-DA/DOX offers remarkably improved cell killing for drug-resistant cancer cells under the tumor microenvironmental pH in comparison with free DOX. Exploiting its excellent photothermal conversion ability, combined chemo- and photothermal therapy is further demonstrated using NGO-PEG-DA/DOX, realizing a synergistic therapeutic effect. This work presents a novel design of surface chemistry on NGO for the development of smart drug delivery systems responding to the tumor microenvironment and external physical stimulus, with the potential to overcome drug resistance.

Drug delivery with PEGylated MoS2 nano-sheets for combined photothermal and chemotherapy of cancer.

MoS2 nanosheets functionalized with poly-ethylene glycol are for the first time used as a multifunctional drug delivery system with high drug loading capacities. Using doxorubicin as the model drug and taking advantages of the strong near-infrared absorbance of MoS2, combined photothermal and chemotherapy of cancer is realized in animal experiments, achieving excellent synergistic anti-tumor effect upon systemic administration.

Solution-processed 2D niobium diselenide nanosheets as efficient hole-transport layers in organic solar cells.

Thin-layer, two-dimensional NbSe2 nanosheets with lower trap density have been obtained and act as an alternative hole-transporting layer to replace MoO3 in organic solar cells. If poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C71-butyric acid methyl ester acts as an active layer, a power conversion efficiency of 8.10 % has been achieved without any further thermal treatment. The properties of this hole-transporting layer were investigated and the improvements in the devices are discussed.

PEGylated WS(2) nanosheets as a multifunctional theranostic agent for in vivo dual-modal CT/photoacoustic imaging guided photothermal therapy.

A new generation of photothermal theranostic agents is developed based on PEGylated WS2 nanosheets. Bimodal in vivo CT/photoacoustic imaging reveals strong tumor contrast after either intratumoral or intravenous injection of WS2 -PEG. In vivo photothermal treatment is then conducted in a mouse tumor model, achieving excellent therapeutic efficacy with complete ablation of tumors. This work promises further exploration of transition-metal dichalcogenides for biomedical applications, such as cancer imaging and therapy.

Surface coating-dependent cytotoxicity and degradation of graphene derivatives: towards the design of non-toxic, degradable nano-graphene.

With the increasing interests of using graphene and its derivatives in the area of biomedicine, the systematic evaluation of their potential risks and impacts to biological systems is becoming critically important. In this work, we carefully study how surface coatings affect the cytotoxicity and extracellular biodegradation behaviors of graphene oxide (GO) and its derivatives. Although naked GO could induce significant toxicity to macrophages, coating those two-dimensional nanomaterials with biocompatible macromolecules such as polyethylene glycol (PEG) or bovine serum albumin (BSA) could greatly attenuate their toxicity, as independently evidenced by several different assay approaches. On the other hand, although GO can be gradually degraded through enzyme induced oxidization by horseradish peroxidase (HRP), both PEG and BSA coated GO or reduced GO (RGO) are rather resistant to HRP-induced biodegradation. In order to obtain biocompatible functionalized GO that can still undergo enzymatic degradation, we conjugate PEG to GO via a cleavable disulfide bond, obtaining GO-SS-PEG with negligible toxicity and considerable degradability, promising for further biomedical applications.

Graphene-based magnetic plasmonic nanocomposite for dual bioimaging and photothermal therapy.

In recent years, graphene and graphene-based nanocomposites owning to their highly enriched physical and chemical properties have been widely explored for applications in many different fields including biomedicine. In the present work, we decorate graphene oxide (GO) by both iron oxide nanoparticles (IONPs) and gold, forming a multi-functional magnetic & plasmonic GO-IONP-Au nanocomposite with strong superparamagnetism and significantly enhanced optical absorbance in the near-infrared (NIR) region. We then coat the nanocomposite with polyethylene glycol (PEG), obtaining GO-IONP-Au-PEG with high stability in physiological environments and no significant in vitro toxicity. Remarkably enhanced photothermal cancer ablation effect using GO-IONP-Au-PEG is realized in comparison to PEGylated GO used in our earlier studies, as demonstrated in both in vitro cell tests and in vivo animal experiments. Moreover, the IONP and Au compartments in the GO-IONP-Au-PEG nanocomposite could be further taken advantages for magnetic resonance (MR) and X-ray dual-modal imaging. Our work shows the promise of using graphene-based multi-functional nanocomposite as cancer theranostics.

In vivo biodistribution and toxicology of functionalized nano-graphene oxide in mice after oral and intraperitoneal administration.

Graphene oxide (GO) and its functionalized derivatives have attracted great attention in biomedicine in recent years. A number of groups including ours have studied the in vivo behaviors of functionalized nano-graphene after intravenous injection or inhalation, and uncovered the surface coating & size dependent biodistribution and toxicology profiles for this type of nanomaterials. However, the fate of GO derivatives in animals after oral feeding and intraperitoneal (i.p.) injection, which are two other major drug administration routes, remain unclear. Therefore, in this work, we sought to systematically investigate in vivo biodistribution and potential toxicity of as-made GO and a number of polyethylene glycol (PEG) functionalized GO derivatives with different sizes and surface coatings, after oral and intraperitoneal administration at high doses. It is found that (125)I labeled PEGylated GO derivatives show no obvious tissue uptake via oral administration, indicating the rather limited intestinal adsorption of those nanomaterials. In contrast, high accumulation of PEGyalted GO derivatives, but not as-made GO, in the reticuloendothelial (RES) system including liver and spleen is observed after i.p. injection. Further investigations based on histological examination of organ slices and hematological analysis discover that although GO and PEGylated GO derivatives would retain in the mouse body over a long period of time after i.p. injection, their toxicity to the treated animals is insignificant. Our work is an important fundamental study that offers a deeper understanding of in vivo behaviors and toxicology of functionalized nano-graphene in animals, depending on their different administration routes.

Polyethylene glycol and polyethylenimine dual-functionalized nano-graphene oxide for photothermally enhanced gene delivery.

Graphene oxide (GO) has been extensively explored in nanomedicine for its excellent physiochemical, electrical, and optical properties. Here, polyethylene glycol (PEG) and polyethylenimine (PEI) are covalently conjugated to GO via amide bonds, obtaining a physiologically stable dual-polymer-functionalized nano-GO conjugate (NGO-PEG-PEI) with ultra-small size. Compared with free PEI and the GO-PEI conjugate without PEGylation, NGO-PEG-PEI shows superior gene transfection efficiency without serum interference, as well as reduced cytotoxicity. Utilizing the NIR optical absorbance of NGO, the cellular uptake of NGO-PEG-PEI is shown to be enhanced under a low power NIR laser irradiation, owing to the mild photothermal heating that increases the cell membrane permeability without significantly damaging cells. As the results, remarkably enhanced plasmid DNA transfection efficiencies induced by the NIR laser are achieved using NGO-PEG-PEI as the light-responsive gene carrier. More importantly, it is shown that our NGO-PEG-PEI is able to deliver small interfering RNA (siRNA) into cells under the control of NIR light, resulting in obvious down-regulation of the target gene, Polo-like kinase 1 (Plk1), in the presence of laser irradiation. This study is the first to use photothermally enhanced intracellular trafficking of nanocarriers for light-controllable gene delivery. This work also encourages further explorations of functionalized nano-GO as a photocontrollable nanovector for combined photothermal and gene therapies.

Nano-graphene in biomedicine: theranostic applications.

Owing to their unique physical and chemical properties, graphene and its derivatives such as graphene oxide (GO), reduced graphene oxide (RGO) and GO-nanocomposites have attracted tremendous interest in many different fields including biomedicine in recent years. With every atom exposed on its surface, single-layered graphene shows ultra-high surface area available for efficient molecular loading and bioconjugation, and has been widely explored as novel nano-carriers for drug and gene delivery. Utilizing the intrinsic near-infrared (NIR) optical absorbance, in vivo graphene-based photothermal therapy has been realized, achieving excellent anti-tumor therapeutic efficacy in animal experiments. A variety of inorganic nanoparticles can be grown on the surface of nano-graphene, obtaining functional graphene-based nanocomposites with interesting optical and magnetic properties useful for multi-modal imaging and imaging-guided cancer therapy. Moreover, significant efforts have also been devoted to study the behaviors and toxicology of functionalized nano-graphene in animals. It has been uncovered that both surface chemistry and sizes play key roles in controlling the biodistribution, excretion, and toxicity of nano-graphene. Biocompatibly coated nano-graphene with ultra-small sizes can be cleared out from body after systemic administration, without rendering noticeable toxicity to the treated mice. In this review article, we will summarize the latest progress in this rapidly growing field, and discuss future prospects and challenges of using graphene-based materials for theranostic applications.

Multimodal imaging guided photothermal therapy using functionalized graphene nanosheets anchored with magnetic nanoparticles.

In this work, a nanoscale reduced graphene oxide-iron oxide nanoparticle (RGO-IONP) complex is noncovalently functionalized with polyethylene glycol (PEG), obtaining a RGO-IONP-PEG nanocomposite with excellent physiological stability, strong NIR optical absorbance, and superparamagnetic properties. Using this theranostic nanoprobe, in-vivo triple modal fluorescence, photoacoustic, and magnetic resonance imaging are carried out, uncovering high passive tumor targeting, which is further used for effective photothermal ablation of tumors in mice.