Dechang Jia

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3and hydroxyapatite.

Three-dimensional graphene oxide/polypyrrole composite electrodes fabricated by one-step electrodeposition for high performance supercapacitors

Three-dimensional (3D) graphene oxide/polypyrrole (GO/PPy) composite electrodes have been fabricated via one-step electrochemical co-deposition in an aqueous solution containing pyrrole monomers, GO and LiClO4. The concentration of GO in the solution plays an important role in controlling the morphologies of the as-deposited GO/PPy composites, and a relatively low concentration of 0.1 mg mL−1 is favorable for the formation of a 3D interconnected structure. The unique 3D interconnected structure ensures fast diffusion of electrolyte ions through the electrode. As a result, the GO/PPy composite electrode with a mass loading of 0.26 mg cm−2 exhibits the highest specific capacitance of 481.1 F g−1, while the electrode with a larger mass loading of 1.02 mg cm−2 delivers the best area capacitance of 387.6 mF cm−2, at a current density of 0.2 mA cm−2. Moreover, the GO/PPy composite electrodes exhibit good rate capability with capacitance retentions over 80% when the current density load increases from 0.2 to 10 mA cm−2. Both the aqueous and solid-state supercapacitors based on GO/PPy composite electrodes show excellent capacitive properties with good cycling stability, indicating their suitability for applications in energy storage and management.

High-yield synthesis of strong photoluminescent N-doped carbon nanodots derived from hydrosoluble chitosan for mercury ion sensing via smartphone APP.

Photoluminescent carbon nanodots (CNDs) have offered considerable potential to be used in biomedical and environmental fields including live cell imaging and heavy metal ion detection due to their superior quantum emission efficiencies, ability to be functionalized using a variety of chemistries and apparent absence of toxicity. However, to date, synthetic yield of CNDs derived from biomass via hydrothermal carbonization is quite low. We report here the synthesis of nitrogen-doped carbon nanodots (N-doped CNDs) derived from hydrosoluble chitosan via hydrothermal carbonization. The synthetic yield could reach 38.4% which is 2.2-320 times increase compared with that from other biomass reported so far. These N-doped CNDs exhibited a high quantum yield (31.8%) as a consequence of nitrogen incorporation coincident with multiple types of functional groups (C=O, O-H, COOH, and NH2). We further demonstrate applications of N-doped CNDs as probes for live cell multicolor imaging and heavy metal ion detection. The N-doped CNDs offered potential as mercury ion sensors with detection limit of 80nM. A smartphone application (APP) based on N-doped CNDs was developed for the first time providing a portable and low cost detection platform for detection of Hg(2+) and alert of heavy metal ions contamination.

Gradient Structural Bone-Like Apatite Induced by Chitosan Hydrogel via Ion Assembly

Polymers with negatively charged groups (−COOH, −OH or −PO4H2) were frequently adopted to induce or promote apatite deposition through electrostatic interaction. However, chitosan with positively charged groups (−NH2) was ignored, although it could bind most of metal ions through chelation. Based on the chelation properties of the amino group, a chitosan hydrogel obtained via physical cross-linking was used as template for ion assembly. Gradient structural bone-like apatite induced by chitosan hydrogel was achieved via ion assembly within a few hours under ambient conditions, in which amino groups of chitosan acted as anchors between chitosan and apatite nucleation. The phase and component of bone-like apatite were similar to apatite in rabbit ribs according to XRD patterns and FT-IR spectra. XRD results revealed that bone-like apatite was carbonated apatite and preferred growth orientation in the direction of c-axis. The profile of elements distribution in chitosan suggested that the content of calcium and phosphorous elements decreased with the increase of depth along the radius direction, which was accompanied by the formation of apatite-rich regions near the outer layer. When chitosan was dipped in calcium ions solution, Ca2+ ions bound amino groups of chitosan and formed chitosan/calcium ions complexes (CS–NH2…Ca2+). CS–NH2…Ca2+ subsequently attracted negatively-charged phosphate ions through electrostatic interaction. When ion assembly finished, Ca and P ions in the chitosan hydrogel converted into ACP with Ca/P ratio of 1.19. ACP converted into bone-like apatite with Ca/P ratio of 2.01 after alkali treatment.

Hydrosoluble, UV-crosslinkable and injectable chitosan for patterned cell-laden microgel and rapid transdermal curing hydrogel in vivo.

Natural and biodegradable chitosan with unique amino groups has found widespread applications in tissue engineering and drug delivery. However, its applications have been limited by the poor solubility of native chitosan in neutral pH solution, which subsequently fails to achieve cell-laden hydrogel at physiological pH. To address this, we incorporated UV crosslinking ability in chitosan, allowing fabrication of patterned cell-laden and rapid transdermal curing hydrogel in vivo. The hydrosoluble, UV crosslinkable and injectable N-methacryloyl chitosan (N-MAC) was synthesized via single-step chemoselective N-acylation reaction, which simultaneously endowed chitosan with well solubility in neutral pH solution, UV crosslinkable ability and injectability. The solubility of N-MAC in neutral pH solution increased 2.21-fold with substitution degree increasing from 10.9% to 28.4%. The N-MAC allowed fabrication of cell-laden microgels with on-demand patterns via photolithography, and the cell viability in N-MAC hydrogel maintained 96.3 ± 1.3% N-MAC allowed rapid transdermal curing hydrogel in vivo within 60s through minimally invasive clinical surgery. Histological analysis revealed that low-dose UV irradiation hardly induced skin injury and acute inflammatory response disappeared after 7 days. N-MAC would allow rapid, robust and cost-effective fabrication of patterned cell-laden polysaccharide microgels with unique amino groups serving as building blocks for tissue engineering and rapid transdermal curing hydrogel in vivo for localized and sustained protein delivery.

Synergistic effects of surface chemistry and topologic structure from modified microarc oxidation coatings on Ti implants for improving osseointegration.

Microarc oxidation (MAO) coating containing Ca, P, Si, and Na elements on a titanium (Ti) implant has been steam-hydrothermally treated and further mediated by post-heat treatment to overcome the compromised bone-implant integration. The bone regeneration, bone-implant contact, and biomechanical push-out force of the modified Ti implants are discussed thoroughly in this work. The best in vivo performances for the steam-hydrothermally treated one is attributed to the synergistic effects of surface chemistry and topologic structure. Through post-heat treatment, we can decouple the effects of surface chemistry and the nanoscale topologic structure easily. Attributed to the excellent in vivo performance of the surface-modified Ti implant, the steam-hydrothermal treatment could be a promising strategy to improve the osseointegration of the MAO coating covered Ti implant.

Vertically aligned two-dimensional SnS2 nanosheets with a strong photon capturing capability for efficient photoelectrochemical water splitting

Two-dimensional (2D) metal dichalcogenides have emerged as attractive materials for application in photoelectrochemical (PEC) water splitting due to their unique structure and strong interaction with light. To date, deposition of exfoliated 2D nanosheet dispersions onto conductive substrates by a variety of techniques (e.g. casting, spin-coating and self-assembly) has been the most exploited approach to fabricate photoelectrodes from these materials. However, such solution processing strategies do not allow for control over the flake orientation and formation of intimate electrical contacts with conductive substrates. This could negatively affect the PEC efficiency. Herein, we demonstrate, for the first time, vertically aligned 2D SnS2 nanosheets with controllable growth and density on conductive substrates (FTO and carbon cloth (CC)) by a modified chemical vapor deposition (CVD) method. In PEC measurements, these vertically aligned 2D SnS2 nanosheet photoelectrodes exhibit a high incident photon to current conversion efficiency (IPCE) of up to 40.57% for SnS2⊥CC and 36.76% for SnS2⊥FTO at 360 nm, and a high photocurrent density of up to 1.92 ± 0.01 mA cm−2 for SnS2⊥CC and 1.73 ± 0.01 mA cm−2 for SnS2⊥FTO at 1.4 V vs. reversible hydrogen electrode (RHE). These values are two times higher than that of their photoelectrode (SnS2//FTO) counterparts prepared by conventional spin-coating. Our demonstration of this controllable growth strategy offers a versatile framework towards the design and fabrication of high performance PEC photoelectrodes based on 2D metal chalcogenides.

A facile approach to construct BiOI/Bi5O7I composites with heterostructures: efficient charge separation and enhanced photocatalytic activity

A series of BiOI/Bi5O7I composite photocatalysts with heterostructures was successfully synthetized through a facile hydrothermal method. Attributed to the heterostructure between BiOI and Bi5O7I, photogenerated electrons and holes can be separated efficiently. The photocatalytic activity of the as-prepared samples was evaluated through the MO degradation reaction. The removal rate of MO was up to 93% after 40 min under visible light (λ ≥ 400 nm) irradiation, while the photocatalytic activity showed no decay after 3 cycles. Furthermore, the photocatalytic mechanism of MO degradation over the BiOI/Bi5O7I composite photocatalyst was investigated by taking TA, H2O2 and EDTA as probes. The experimental results indicate that the enhanced photocatalytic performance is attributed to the synergistic effect of photogenerated holes and superoxide radicals. The excellent activity and photostability reveal that the BiOI/Bi5O7I composite photocatalyst is a promising visible-light-response photocatalyst with potential applications in the field of water treatment.

Structure, MC3T3-E1 Cell Response, and Osseointegration of Macroporous Titanium Implants Covered by a Bioactive Microarc Oxidation Coating with Microporous Structure

Macroporous Ti with macropores of 50-400 μm size is prepared by sintering Ti microbeads with different diameters of 100, 200, 400, and 600 μm. Bioactive microarc oxidation (MAO) coatings with micropores of 2-5 μm size are prepared on the macroporous Ti. The MAO coatings are composed of a few TiO2 nanocrystals and lots of amorphous phases with Si, Ca, Ti, Na, and O elements. Compared to compact Ti, the MC3T3-E1 cell attachment is prolonged on macroporous Ti without and with MAO coatings; however, the cell proliferation number increases. These results are contributed to the effects of the space structure of macroporous Ti and the surface chemical feature and element dissolution of the MAO coatings during the cell culture. Macroporous Ti both without and with MAO coatings does not cause any adverse effects in vivo. The new bone grows well into the macropores and micropores of macroporous Ti with MAO coatings, showing good mechanical properties in vivo compared to Ti, MAO-treated Ti, and macroporous Ti because of its excellent osseointegration. Moreover, the MAO coatings not only show a high interface bonding strength with new bones but also connect well with macroporous Ti. Furthermore, the pushing out force for macroporous Ti with MAO coatings increases significantly with increasing microbead diameter.

Mineralization of chitosan rods with concentric layered structure induced by chitosan hydrogel

Ca ions and P ions absorbed by chitosan hydrogel with a molar ratio of 1.19 were converted into carbonated apatite under ambient condition, by alternate soaking in combination with alkali treatment within a few hours. The alkali treatment helped to convert amorphous calcium phosphate in chitosan hydrogel into carbonated apatite. The bending strength of mineralized chitosan with a concentric layered structure varied from 62.7 MPa to 92.5 MPa, which was 45.8-67.5% as strong as that of rabbit femur. During the process of alternate soaking and alkali treatment, chitosan hydrogel not only provided a medium for the carbonated apatite coating reaction which helped to form the concentric layered structure due to the Liesegang rings phenomenon, but also induced absorption of Ca and P ions in the hydrogel framework via chelation or electrostatic interaction rather than the diffusion model originated from the concentration gradient.