Molybdenum disulfide (MoS2) nanosheets are gaining increasing attention due to their attractive properties and myriads of potential applications. However, challenges in the enhancement of their colloidal stability and surface functionality still remain and significantly restrict their practical applications. Herein, we present a viable approach to functionalize MoS2 nanosheets with multihydroxy hyperbranched polyglycerol (HPG) shell by surface-initiated ring-opening polymerization technique. The grafting of HPG from the surface of MoS2 nanosheet yielded MoS2-g-HPG nanohybrid with excellent water dispersibility, good biocompatibility, and greatly enhanced colloidal stability against pH change, ionic strength variation and long-term storage. The MoS2-g-HPG also exhibited excellent light-to-heat conversion capability for in vitro photothermal therapy application. Meanwhile, the MoS2-g-HPG showed favorable surface functionality owing to its numerous surface hydroxyl groups, as demonstrated by the conjugation of functional molecules such as fluorescent dye rhodamine B. As such, this paper opens up new opportunities to empower MoS2 nanosheets and other two-dimensional inorganic nanosheets with desired properties for various applications.Download high-res image (210KB)Download full-size image

Synthesis of fluorescent carbide-derived carbons (CDCs) remains a big challenge for material scientists. Herein, we report an unprecedented method for the synthesis of amphiphilic carbide-derived graphene quantum dots (GQDs) from layered Ti3C2Tx MXene using solvothermal treatment of Ti3C2Tx MXene in dimethylformamide (DMF). Our findings indicate that DMF can simultaneously act as reaction media and nitrogen-doping agent for the formation of highly fluorescent carbide-derived GQDs. The resulted GQDs with uniform size distribution exhibit excellent dispersibility in both hydrophilic solvents (e.g., water, DMF, and ethanol) and in hydrophobic solvents (e.g., chloroform and toluene). With their superior properties of bright and tunable photoluminescence, low cytotoxicity, good photostability and chemical inertness, the carbide-derived GQDs are promising for applications in fluorescent ink, light-emitting composites and cellular imaging as demonstrated in this paper. This work opens a new route towards the large-scale synthesis of high-quality GQDs, paving the way for their versatile applications.Download high-res image (410KB)Download full-size image

This study proposes a simple method to fabricate a magnetic self-healing poly(vinyl alcohol) (ms-PVA) composite hydrogel. The obtained ms-PVA hydrogel was characterized by vibrating sample magnetometery and transmission electron microscopy. The self-healing property was investigated using a rheometer and tensile strength tests. Results showed that the ms-PVA hydrogel exhibited an excellent self-healing property and controllable magnetic intensity by adjusting the Fe3O4 particle content. The added Fe3O4 particles did not participate in hydrogen bond interactions but did cause the magnetic properties of the hydrogel. The hydrogel showed the best self-healing performance when the amount of Fe3O4 particles was 5 wt% (based on ms-PVA). The ms-PVA composite hydrogel presents a new application of the PVA hydrogel given its facile fabrication process and excellent performance.

Fluorescent carbon dots (CDs) hold great promise for a myriad applications due to their fascinating attributes. However, the development of CDs with high fluorescence quantum yield (QY) and unique surface property is still in its infancy. Herein, we report a simple and green strategy to produce water-soluble nitrogen-doped CDs (N-CDs) via the one-pot hydrothermal carbonization of the mixture of natural peach gum polysaccharide (PGP) and ethylenediamine. The resulting N-CDs exhibit a remarkably enhanced QY (28.46%) as compared with that of undoped CDs (5.31%). In addition, the N-CDs show stable fluorescence against ionic strength variation and pH change. Preliminary biological studies reveal that N-CDs possess low cytotoxicity and high fluorescent contrast in cells. Moreover, we present here for the first time that the obtained N-CDs can exhibit a fast and highly sensitive and selective fluorescence quenching effect toward Au3+ ions. The detection limit can reach 6.4 × 10–8 M, which compares favorably to other reported fluorescent probes. We have also demonstrated that the N-CDs can be employed to sense Au3+ ions in real river water. Considering the easy synthetic process and excellent performance of the N-CDs, this investigation opens up new opportunities for preparing high-quality fluorescent CDs to meet the requirement of many applications.Keywords: Bioimaging; Fluorescence; Nitrogen-doped carbon dots; Selectivity; Sensing of Au3+ ions

•Versatile PMMA/CNF–NaYF4:Yb/Er composite microspheres (CRs) were easily fabricated.•The CRs simultaneously exhibited upconversion and downconversion luminescence.•The NaYF4:Yb/Er nanoparticles can facilitate the formation of CRs.•The CRs also presented excellent drug delivery performance.Composite microspheres (CRs) assembled from various functional materials have been considered as excellent candidates for many applications. Herein, we report a straightforward method to fabricate multifunctional model drug methyl red-loaded polymethyl methacrylate (PMMA)/cellulose nanofiber (CNF)–NaYF4:Yb/Er CRs by Pickering emulsion system. The obtained CRs were characterized by optical microscope, scanning electric microscope, and emission spectrum. The results revealed that the CRs with relatively uniform size distribution exhibited both strong upconversion and downconversion luminescence and fine drug release performance. Considering the facile operation process and versatile properties of the CRs, this work offers an easy and universal method to prepare various multifunctional CRs for meeting the requirements of diverse applications.

Two dimensional MoS2 nanosheets decorated with inorganic nanoparticles (INPs) are emerging as novel MoS2-based nanohybrids for tuning the intrinsic attributes of both components for fundamental research and technological applications. However, the design and fabrication of MoS2–INP nanohybrids with a tailor-made structure and functions remain a significant challenge. Herein we report a general and controllable protocol for the one-step synthesis of various MoS2–INP nanohybrids by employing carboxylic MoS2 (MoS2–COOH) nanosheets as a versatile support. The obtained MoS2–INP nanohybrids exhibit good dispersibility, high reactivity and excellent processability. The size, morphology and coverage density of INPs on the surface of MoS2–COOH can be readily controlled by tuning the feed ratio. Control experiments reveal that the presence of carboxylic functional groups plays a key role in controlling the structure and properties of the resulting MoS2–INP nanohybrids. In addition, ternary MoS2-based nanohybrids can also be readily prepared by this approach, as exemplified by the synthesis of MoS2–Fe3O4/Pt nanohybrids, which simultaneously exhibit excellent catalytic performance toward the reduction of 4-nitrophenol and favorable magnetic separation capability. Considering the simple fabrication process, high controllability of this protocol and excellent performance of the product, the present work opens up enormous opportunities for the large-scale production of diverse MoS2-based nanohybrids for many technological applications.

Graphene oxide (GO) is emerging as a potential adsorbent for environmental cleanup due to its attractive attributes associated with high removal efficiency toward water pollutants. However, it is difficult to separate GO from water after adsorption. Until now, the development of an effective approach that can simultaneously take advantage of the adsorption feature of GO and overcome the separation problem is still a challenge. Herein, we demonstrate a simple one-step approach to fabricate magnetic GO/poly(vinyl alcohol) (PVA) composite gels (mGO/PVA CGs), which not only exhibit convenient magnetic separation capability but also show remarkably enhanced adsorption capacity for cationic methylene blue (MB) and methyl violet (MV) dyes as compared with the one without GO (e.g., the adsorption capacities of mGO/PVA-50% and mGO/PVA-0% for MB are 231.12 and 85.64 mg/g, respectively). Detailed adsorption studies reveal that the adsorption kinetics and isotherms can be well-described by pseudo-second-order model and Langmuir isotherm model, respectively. Moreover, the adsorbent could be well regenerated in an acid solution without obvious compromise of removal efficiency. Considering the facile fabrication process and robust adsorption performance of the mGO/PVA CG, this work opens up enormous opportunities to bring GO from experimental research to practical water treatment applications. In addition, the mGO/PVA CG can act as a magnetic support for in situ growth of noble metal nanocatalyst with excellent catalytic performance, as exemplified by the synthesis of mGO/PVA-Pt catalyst in this paper.Keywords: Adsorption; Catalysis; Dye; Graphene oxide; Magnetic composite gel; Reduction of 4-nitrophenol;

Decoration of lanthanide-doped upconversion nanoparticles (UCNPs) with polymers to endow the UCNPs with the desired properties for various applications has attracted considerable attention. Herein, we present for the first time that the surface-initiated cationic ring-opening polymerization (CROP) technique can be employed as an effective tool to decorate UCNP with diverse polymers, as exemplified by the successful grafting of hydrophobic poly(ε-caprolactone) and hydrophilic hyperbranched polyglycerol from the surface of NaYF4:Yb/Er UCNP. Furthermore, the content of the grafted polymer associated with the thickness of the polymer shell can be controlled by adjusting the feed ratio. Benefiting from the introduction of the polymer shell, the resulting UCNP/polymer nanohybrids simultaneously show strong upconversion luminescence, tunable solution dispersibility, enhanced solution processibility, high biocompatibility, and favorable surface functionality, which make them promising for various applications such as fabrication of light-emitting polymer composites, cellular imaging, and drug delivery. Considering the high robustness and flexibility of the CROP technique, this investigation opens up new avenues for decorating UCNPs with diverse polymers to meet various application requirements.

•One-step synthesis of multihydroxy Fe3O4/HPG nanoparticle is reported.•The Fe3O4/HPG shows uniform size, excellent water-dispersibility and magnetic property.•The surface property of Fe3O4/HPG nanoparticle can be readily tailored.•Tailoring the surface of Fe3O4/HPG to afford multicarboxylic Fe3O4/HPG-COOH is reported.•The Fe3O4/HPG-COOH can work as a high-performance magnetic adsorbent toward cationic dyes.A straightforward approach for fabricating multihydroxy hyperbranched polyglycerol (HPG) capped Fe3O4 (Fe3O4/HPG) nanoparticles is reported. The obtained Fe3O4/HPG nanoparticles with numerous surface hydroxyl groups show uniform size and shape, excellent water-dispersibility, and strong magnetic property. The surface property of Fe3O4/HPG nanoparticles can be readily tailored as confirmed by preparing multicarboxylic Fe3O4/HPG-COOH nanoparticles in this paper. On the basis of their excellent magnetic performance and multiple negatively charged carboxylic groups, the Fe3O4/HPG-COOH nanoparticles can be utilized as an efficient adsorbent to remove cationic dyes from water. Moreover, they can be regenerated and reused for several times without compromise of adsorption efficiency.

Upconversion nanoparticle (UCNP) as a new class of imaging agent is gaining prominence because of its unique optical properties. An ideal UCNP for bioimaging should simultaneously possess fine water dispersibility and favorable functional groups. In this paper, we present a simple but effective method to the synthesis of a UCNP-based nanohybrid bearing a multihydroxy hyperbranched polyglycerol (HPG) shell by the combination of a “grafting from” strategy with a ring-opening polymerization technique. The structure and morphology of the resulting UCNP-g-HPG nanohybrid were characterized in detail by Fourier transform infrared, 1H NMR, thermogravimetric analysis, and transmission electron microscopy measurements. The results reveal that the amount of grafted HPG associated with the thickness of the HPG shell can be well tuned. UCNP-g-HPG shows high water dispersibility and strong and stable upconversion luminescence. On the basis of its numerous surface hydroxyl groups, UCNP-g-HPG can be tailored by a representative fluorescent dye rhodamine B to afford a UCNP-g-HPG-RB nanohybrid that simultaneously presents upconversion and downconversion luminescence. Preliminary biological studies demonstrate that UCNP-g-HPG shows low cytotoxicity, high luminescent contrast, and deep light penetration depth, posing promising potential for bioimaging applications.Keywords: bioimaging; hyperbranched polyglycerol; surface functionality; upconversion nanoparticle; water dispersibility;

•Peach gum (PG) polysaccharide was studied as a polyelectrolyte for the first time.•A hydrolysis mechanism is proposed for preparing hydrolyzed PG polysaccharide (HPGP).•The HPGP with multiple carboxylic groups possesses negative charges in water.•The HPGP shows remarkable pH and ionic strength responsiveness.•The utilization of HPGP for layer-by-layer self-assembly application is studied.The hydrolyzed peach gum polysaccharide (HPGP) prepared at acidic condition is investigated as an anionic polyelectrolyte for the first time. A hydrolysis mechanism is proposed by monitoring the hydrolysis efficiency and morphological change of crude peach gum, and the intrinsic viscosity of resulted HPGP as a function of hydrolysis time. Fourier transform infrared (FTIR) spectroscopy and ζ-potential measurements reveal that HPGP with multiple carboxylic groups is negatively charged in water in the pH range 3–11. The HPGP exhibits remarkable pH and ionic strength responsiveness, as proven by dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements. Moreover, the layer-by-layer (LbL) self-assembly experiments further confirmed that the HPGP can be utilized as an anionic polyelectrolyte. Considering the facile availability, favorable compatibility and intriguing functionality of HPGP, this study opens up enormous opportunities for the large-scale utilization of peach gum resource.

•The potential of peach gum (PG) for the removal of dye from water was studied.•The PG can efficiently adsorb high amounts of cationic dyes from water.•The adsorption kinetics described well by the pseudo-second-order model.•The adsorption isotherm data were fitted well to Langmuir isotherm.•The PG can be regenerated and used repeatedly.This study investigated the potential use of natural peach gum (PG) as alternative adsorbent for the removal of dyes from aqueous solutions. The PG showed high adsorption capacities and selectivity for cationic dyes (e.g., methylene blue (MB) and methyl violet (MV)) in the pH range 6–10. 98% of MB and MV could be adsorbed within 5 min, and both of the adsorptions reached equilibrium within 30 min. The dye uptake process followed the pseudo-second-order kinetic model. The intraparticle diffusion was not the sole rate controlling step. Equilibrium adsorption isotherm data indicated a good fit to the Langmuir isotherm model. Regeneration study revealed that PG could be well regenerated in acid solution. The recovered PG still exhibited high adsorption capacity even after five cycles of desorption–adsorption. On the basis of its excellent adsorption performance and facile availability, PG can be employed as an efficient low cost adsorbent for environmental cleanup.

Two-dimensional layered MoS2 nanosheets exhibit a wide range of attractive properties and hold great promise in myriad fields. However, the poor performance of surface functionality greatly limits their applications. In this paper, we report on a facile approach to direct synthesis of organic functional group decorated MoS2 (OFGD-MoS2) nanosheets based on the simultaneous exfoliation of bulk MoS2 crystals and chemical conjugation of thiol ligands. The morphology and structure of OFGD-MoS2 nanosheets are systematically characterized using microscopy (TEM, SEM, AFM), thermal gravimetric analysis (TGA), and spectroscopy (Raman, FTIR, XPS) measurements. The content of attached functional groups can be controlled simply by changing the experimental conditions. Furthermore, the introduced functional groups show excellent structural stability and high chemical reactivity, making them promising for further modification as confirmed by the in situ growth of inorganic nanoparticles and polymers. In addition, surface functionalized WS2 nanosheets can also be synthesized by this approach. This investigation paves the way for the synthesis and applications of advanced MoS2-based materials.

•One-step synthesis for water-dispersible NaYF4:Yb/Er upconversion nanoparticles is presented.•The NaYF4:Yb/Er nanoparticles possess hexagonal phase structure.•They show excellent water-dispersibility and strong upconversion luminescence.•Their surface hydroxyl groups are reactive for further modification.Rare-earth upconversion nanophosphors (UCNPs) with high water-dispersibility and surface functional groups are promising for bioimaging. In this paper, we reported a facile strategy for one-step synthesis of water-dispersible hydroxyl-functionalized NaYF4:Yb/Er UCNPs based on the solvothermal technique by using ricinoleic acid as ligand. TEM and XRD characterizations indicate that the synthesized UCNPs possess hexagonal phase structure and spherical shape with a mean diameter of 20 nm. The UCNPs show excellent water-dispersibility and strong upconversion luminescence. Moreover, the presence of hydroxyl groups on the surface of NaYF4:Yb/Er allows for further modification as confirmed by the successful reaction with dodecanoyl chloride. Our strategy opens up opportunities to make full use of water-dispersible UCNPs in various applications because of their facile availability, cost-effective productivity and favorable surface functionality.

Magnetic iron oxide nanoparticles (MIONs) bearing amine and vinyl groups are fabricated straightforwardly using vinyl-based tertiary amine molecules as both alkaline source and ligands based on the coprecipitation of iron ions in aqueous solution. The as-prepared MIONs present amphiphilic performance that can be well-dispersed both in aqueous solution and common organic solvents (e.g., ethanol, dichloromethane and tetrahydrofuran). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) measurements reveal that the MIONs are superparamagnetic Fe3O4 nanoparticles with a mean diameter below 10 nm. The presence of ligands on the surface of MIONs was confirmed by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) characterizations. Benefiting from the surface vinyl groups, the MIONs are able to graft polyvinyl-based polymers by in situ polymerization of the corresponding vinyl monomers as confirmed by grafting poly(methyl methacrylate) (PMMA) in this paper. On the basis of their surface amine groups, the MIONs show high adsorption capacity (ca. 0.42 mmol/g) for congo red dye and excellent performance for in situ growth of Pt nanocatalyst. Moreover, the MIONs possess high stability and can be reused several times without obvious decrease of their adsorption capacity and catalytic efficiency. Considering the facile fabrication process and versatile performance of the obtained MIONs, this work may open up new opportunities for the large-scale applications of MIONs.Keywords: catalysis; dye adsorption; magnetic iron oxide; nanoparticles; polymer grafting;

A facile and green approach for the synthesis of amphibious fluorescent carbon dots (CDs) from natural polysaccharide is reported. Light-emitting polymer nanocomposites with excellent optical performance can be easily prepared by incorporation of the amphibious CDs into the polymer matrix.

•Magnetic carboxymethyl starch/poly(vinyl alcohol) (mCMS/PVA) hydrogel was prepared by a one-step method.•The mCMS/PVA exhibited high removal efficiency for cationic methylene blue dye.•Adsorption process of mCMS/PVA fitted pseudo-second-order model and Freundlich isotherm.•The mCMS/PVA presented good reusability and easy magnetic separation property.This study presents a simple method to fabricate magnetic carboxymethyl starch/poly(vinyl alcohol) (mCMS/PVA) composite gel. The obtained mCMS/PVA was characterized by Fourier transform infrared (FTIR) spectra, vibrating-sample magnetometer (VSM) and scanning electron microscopy (SEM) measurements. The application of mCMS/PVA as an adsorbent for removal of cationic methylene blue (MB) dye from water was investigated. Benefiting from the combined merits of carboxymethyl starch and magnetic gel, the mCMS/PVA simultaneously exhibited excellent adsorption property toward MB and convenient magnetic separation capability. The effects of initial dye concentration, contact time, pH and ionic strength on the adsorption performance of mCMS/PVA adsorbent were investigated systematically. The adsorption process of mCMS/PVA for MB fitted pseudo-second-order model and Freundlich isotherm. Moreover, desorption experiments revealed that the mCMS/PVA adsorbent could be well regenerated in ethanol solution without obvious compromise of removal efficiency even after eight cycles of desorption/adsorption. Considering the facile fabrication process and robust adsorption performance, the mCMS/PVA composite gel has great potential as a low cost adsorbent for environmental decontamination.Download full-size image

A facile and green approach for the synthesis of amphibious fluorescent carbon dots (CDs) from natural polysaccharide is reported. Light-emitting polymer nanocomposites with excellent optical performance can be easily prepared by incorporation of the amphibious CDs into the polymer matrix.

Two dimensional MoS2 nanosheets decorated with inorganic nanoparticles (INPs) are emerging as novel MoS2-based nanohybrids for tuning the intrinsic attributes of both components for fundamental research and technological applications. However, the design and fabrication of MoS2–INP nanohybrids with a tailor-made structure and functions remain a significant challenge. Herein we report a general and controllable protocol for the one-step synthesis of various MoS2–INP nanohybrids by employing carboxylic MoS2 (MoS2–COOH) nanosheets as a versatile support. The obtained MoS2–INP nanohybrids exhibit good dispersibility, high reactivity and excellent processability. The size, morphology and coverage density of INPs on the surface of MoS2–COOH can be readily controlled by tuning the feed ratio. Control experiments reveal that the presence of carboxylic functional groups plays a key role in controlling the structure and properties of the resulting MoS2–INP nanohybrids. In addition, ternary MoS2-based nanohybrids can also be readily prepared by this approach, as exemplified by the synthesis of MoS2–Fe3O4/Pt nanohybrids, which simultaneously exhibit excellent catalytic performance toward the reduction of 4-nitrophenol and favorable magnetic separation capability. Considering the simple fabrication process, high controllability of this protocol and excellent performance of the product, the present work opens up enormous opportunities for the large-scale production of diverse MoS2-based nanohybrids for many technological applications.