Research Article Online first
Biomimetic chitin hydrogel via chemical transformation
Nano Research
Published: 01 July 2023

Chitin hydrogel has been recognized as a promising material for various biomedical applications because of its biocompatibility and biodegradability. However, the fabrication of strong chitin hydrogel remains a big challenge because of the insolubility of chitin in many solvents and the reduced chain length of chitin regenerated from solutions. We herein introduce the fabrication of chitin hydrogel with biomimetic structure through the chemical transformation of chitosan, which is a water-soluble deacetylated derivative of chitin. The reacetylation of the amino group in chitosan endows the obtained chitin hydrogel with outstanding resistance to swelling, degradation, extreme temperature and pH conditions, and organic solvents. The chitin hydrogel has excellent mechanical properties while retaining a high water content (more than 95 wt.%). It also shows excellent antifouling performance that it resists the adhesion of proteins, bacteria, blood, and cells. Moreover, as the initial chitosan solution can be feasibly frozen and templated by ice crystals, the chitin hydrogel structure can be either nacre-like or wood-like depending on the freezing method of the precursory chitosan solution. Owing to these anisotropic structures, such chitin hydrogel can exhibit anisotropic mechanics and mass transfer capabilities. The current work provides a rational strategy to fabricate chitin hydrogels and paves the way for its practical applications as a superior biomedical material.

Research Article Issue
Modular divergent creation of dual-cocatalysts integrated semiconducting sulfide nanotriads for enhanced photocatalytic hydrogen evolution
Nano Research 2023, 16 (5): 7967-7973
Published: 23 December 2022

Heteronanostructures (HNs) with precise components and interfaces are important for many applications, such as designing efficient and robust solar-to-fuel catalysts via integrating specific semiconductors with favorable band alignments. However, rationally endowing such features with rigorous framework control remains a synthetic bottleneck. Herein, we report a modular divergent creation of dual-cocatalysts integrated semiconducting sulfide nanotriads (NTds), comprising both isolated PdxS oxidation (ox) and MoS2 reduction (red) domains within each single CdS counterpart, which exhibit superior photocatalytic activity and stability for hydrogen evolution reaction (HER). The stepwise constructed PdxS(ox)−CdS−MoS2(red) NTds possess dual-interfaces facilitating continuous charge separation and segregated active sites accelerating redox reactions, respectively, achieving the HER rate up to 9 mmol·h−1·g−1, which is about 60 times higher than that of bare CdS, and show no evidence of deactivation after long-term cycling. This design principle and transformation protocol provide predictable retrosynthetic pathways to HNs with increased degree of complexity and more elaborate functionalities that are otherwise inaccessible.

Research Article Issue
Phase transformation-induced Mg isotope fractionation in Mg-mediated CaCO3 mineralization
Nano Research 2023, 16 (2): 3597-3602
Published: 05 December 2022

The biomineralization of CaCO3 often involves the transformation of amorphous precursors into crystalline phases, which is regulated by various proteins and inorganic ions such as Mg2+ ions. While the effects of Mg2+ ions on the polymorph and shape of the crystalline CaCO3 have been observed and studied, the interplay between Mg2+ ions and CaCO3 during the mineralization remains unclear. This work focuses on the mechanism of Mg2+ ion-regulated mineralization of CaCO3. By tracing the Mg isotope fractionation, the different mineralization pathways of CaCO3 under different Mg2+ ion concentrations had been clarified. Detailed regulatory role of Mg2+ ions at the different stages of mineralization had been proposed through combining the fractionation data with the analyses of the CaCO3 polymorph and shape evolution. These results provide a clear view of the Mg-mediated crystallization process of amorphous CaCO3, which can be used to finely control the phase of the crystalline products according to different needs.

Research Article Issue
Multiscale cellulose-based fireproof and thermal insulation gel materials with water-regulated forms
Nano Research 2023, 16 (2): 3379-3386
Published: 29 November 2022

Different forms of construction materials (e.g., paints, foams, and boards) dramatically improve the quality of life. With the increasing environmental requirements for buildings, it is necessary to develop a comprehensive sustainable construction material that is flexible in application and exhibits excellent performance, such as fireproofing and thermal insulation. Herein, an adjustable multiform material strategy by water regulation is proposed to meet the needs of comprehensive applications and reduce environmental costs. Multiform gels are constructed based on multiscale cellulose fibers and hollow glass microspheres, with fireproofing and thermal insulation. Unlike traditional materials, this multiscale cellulose-based gel can change forms from dispersion to paste to dough by adjusting its water content, which can realize various construction forms, including paints, foams, and low-density boards according to different scenarios and corresponding needs.

Research Article Issue
Nanosheet-coated synthetic wood with enhanced flame-retardancy by vacuum-assisted sonocoating technique
Nano Research 2022, 15 (10): 9440-9446
Published: 26 July 2022

Compared to natural woods, synthetic woods have superior mechanical stability, thermal insulation, and flame retardancy owing to their hierarchically cellular microstructures and intrinsic advantages of the thermosetting matrix. Increasing the long-time fire resistance is very important to the practical application. In this study, we present a novel coating strategy by a vacuum-assisted sonication technique (sonocoating) with a rectorite nanosheet dispersion to create a uniform nanocoating on the channel walls of synthetic wood. Owing to ultrasonic energy and vacuum pressure, the nanosheet dispersion can penetrate deep down to form a layered nanocoating on the channel surface. The coated synthetic woods can withstand fire (400–600 °C) for more than 10 min with 62% mass retainment, surpassing uncoated synthetic woods and natural woods. Therefore, as a lightweight and strong composite with enhanced flame-retardant performance, the coated synthetic woods have huge potential applications in safe and energy-efficient buildings.

Research Article Issue
Bio-inspired synthesis of transition-metal oxide hybrid ultrathin nanosheets for enhancing the cycling stability in lithium-ion batteries
Nano Research 2022, 15 (6): 5064-5071
Published: 08 April 2022

Constructing two-dimensional (2D) structures for transition-metal oxides (TMOs) can optimize their electronic structures and enable high specific surface areas, thereby offering routes to enhancing the performance of TMOs in energy storage and conversion. However, most 2D TMOs, e.g., Fe2O3, remain so far synthetically challenging due to their intrinsic non-layered structures. Herein, inspired by the mechanism of biomineralization, we report the synthesis of CuO/Fe2O3 hybrid ultrathin nanosheets by using polyvinylpyrrolidone-decorated CuO nanosheets as growth modifiers to modulate the hydrolysis process of Fe2+. The formulated “absorption-and-crystallization” two-step formation processes of such 2D hybrid structures accorded well with the biomineralization scheme in nature. Combining the in-situ transmission electron microscopy (TEM) study, theoretical calculation, and control experiments, we validated that the large density of 2D/2D interfaces enabled by this bio-inspired synthesis process can overcome the self-stacking phenomenon during lithium-ion battery cycling, leading to their high operation stability. This work emphasizes the bio-inspired synthesis of 2D TMOs as a promising pathway toward material design and performance optimization.

Editorial Issue
On the occasion of the 80th birthday of Professor Yitai Qian: Celebrating 60 years of innovation in solid-state chemistry and nanoscience
Nano Research 2021, 14 (10): 3337-3342
Published: 25 September 2021

Research Article Issue
Joule-heated carbonized melamine sponge for high-speed absorption of viscous oil spills
Nano Research 2021, 14 (8): 2697-2702
Published: 12 May 2021

Introducing heating function to oil sorbents opens up a new pathway to the fast cleanup of viscous crude oil spills in situ. The oil sorption speed increases with the rise of the temperature, thus oil sorbents with high heating temperature are desirable. Besides, the oil sorbents also need to be produced environment-friendly. Here we present carbonized melamine-formaldehyde sponges (CMSs) that exhibited superior heating performance and the CMSs could be massively fabricated through a non-polluting pyrolysis process. The conductive CMSs could be heated over 300 °C with a low applied voltage of 6.9 V and keep above 250 °C for 30 min in the air without obvious damage. Such high heating performance enabled heating up the oil spills with a high rate of 2.65 °C·s-1 and 14% improvement of oil sorption coefficient compared with the state-of-the-art value. We demonstrated that one joule-heated CMS could continuously and selectively collect viscous oil spills (9,010 mPa·s) 690 times its own weight in one hour. The CMSs will be a highly competitive sorbent material for the fast remediation of future crude oil spills.

Research Article Issue
Highly stretchable, soft and sticky PDMS elastomer by solvothermal polymerization process
Nano Research 2021, 14 (10): 3636-3642
Published: 23 March 2021

Siloxane rubber shows attractive properties of high stability, elasticity and transparency. Besides, the regulation of its properties renders it widely used in many application fields. However, most of the reported performance improvement methods of siloxane rubber focus on the change of chemical composition of siloxane rubber, including the design of molecular chain and the introduction of other compounds, etc. Such a strategy is still faced with many limitations in practical application. In this work, on the premise of not changing the chemical composition of siloxane rubber, we propose a facile solvothermal polymerization process to change the structure of cross-linking networks, so as to obtain the siloxane rubber with controllable mechanical properties. Compared to the normal curing method, we realized polydimethylsiloxane elastomer (PDMS) with maximum elongation of more than 3, 000% (> 10 times of normally cured one) and tensile modulus lower than 0.15 MPa (< 1/10 of normally cured one). In addition to superior stretchability, it gains extra high softness, stickiness and sensitive response to organic solvents. Based on our solvothermal cured PDMS, its applications in oil collection and organic solvent sensor have been demonstrated. It is expected that this method can be readily utilized widely and shows great application potentials.

Research Article Issue
Printable elastic silver nanowire-based conductor for washable electronic textiles
Nano Research 2020, 13 (10): 2879-2884
Published: 05 October 2020

Printable elastic conductors promote the wide application of consumable electronic textiles (e-textiles) for pervasive healthcare monitoring and wearable computation. To assure a clean appearance, the e-textiles require a washing process to clean up the dirt after daily use. Thus, it is crucial to develop low-cost printable elastic conductors with strong adhesion to the textiles. Here, we report a composite elastic conductor based on Ag nanowires (NWs) and polyurethane elastomer. The composite could be dispersed into ink and easily printed onto textiles. One-step print could form robust conductive coatings without sealing on the textiles. Interestingly, the regional concentration of Ag NWs within the polyurethane matrix was observed during phase inversion, endowing the elastic conductor with a low percolation threshold of 0.12 vol.% and high conductivity of 3,668 S·cm-1. Thanks to the high adhesion of the elastic conductors, the resulted e-textiles could withstand repeated stretching, folding, and machine washing (20 times) without obvious performance decay, which reveals its potential application in consumable e-textiles.

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