Hydrogel
materials have many excellent properties and a wide range
of applications. Recently, a new type of hydrogel has emerged: cellulose
nanofiber (CNF)-based hydrogels, which have three-dimensional nanofiber
networks and unique physical properties. Because CNFs are abundant,
renewable, and biodegradable, they are green and eco-friendly nanoscale
building blocks. In addition, CNF-based hydrogel materials exhibit
excellent mechanical properties and designable functions by different
preparation methods and structure designs, demonstrating huge development
potential. In this Perspective, we summarize the recent progress in
the development of CNF-based hydrogels and introduce their applications
in elastic hydrogels, ionic conduction, water purification, and biomedicine,
highlighting future trends and opportunities for the further development
of CNF-based hydrogels as emerging materials systems.
Upconversion nanoparticles (UCNPs) have gained increasing attention for their wide applications in bioimaging, displays and photovoltaics. However, low efficiency has been an ongoing challenge for further developments. In this work, it is proposed that the ultrasmall size of UCNPs is essential for achieving large enhancement factors and experimentally demonstrated with 4-nm UCNPs. A strategy of plasmonic dual resonance is proposed in which two distinct localized surface plasmon resonance (LSPR) peaks of gold nanorods (GNRs) were designed to perfectly match both the excitation and emission light wavelength of UCNPs. Combining the excitation enhancement and Purcell effect, a huge enhancement factor of tens of thousands-fold is stochastically demonstrated for single UCNPs in solution. The largest overall enhancement region is close to the end of a GNR but not in its central part. The excitation enhancement (up to three orders of magnitude) and the emission enhancement (larger than one order of magnitude) induced by the Purcell effect are experimentally demonstrated separately. This study provides insight into how to achieve a very large upconversion enhancement factor with surface plasmons and will catalyze development of UCNPs' extensive applications.
With the extensive use of palladium derivatives in the industry, their environmental pollution has become more and more serious. Herein, allyl functionalized hydrazone 2D COFs (XB-COFs) were found for selective fluorescent detection of Pd 2+ (detection concentration of 0.29 μM) in water. The stable structure of the hydrazone bond and the complexation ability of allyl to Pd 2+ cause XB-COF to have a good fluorescence sensing effect in both acid and alkaline solutions, and its adsorption capacity for Pd 2+ is up to 120 mg g −1 .During the interaction between XB-COF and Pd 2+ , a part of Pd 2+ can be reduced to Pd nanoparticles with a diameter of about 10 nm. A fluorescent test paper was prepared by the in situ growth of XB-COF onto a filter paper, which can realize visualization detection of Pd 2+ in 10 s with the naked eye or under a 365 nm UV lamp. This is the first time a fluorescent test paper based on in the situ growth of COFs has been applied for the detection of heavy metal ions, which provides a new platform for the application of COF materials in the medical health field, food safety, and environmental protection.
A fluorine-rich ultra-stable fluorescent covalent organic framework for adsorption and detection of pesticides was designed and prepared via the Povarov reaction in a flask.
The widespread use of disposable plastic straws cause serious environmental problems and poses potential threats to human health, while paper straws, their most used alternatives, are not so satisfactory due to poor mechanical performance and unpleasant user experience. Here, a new kind of edible and microplastic-free straw made from bacterial cellulose (BC) by biosynthesis is reported. Through the alginate coating, this BC-based straw achieves better mechanical performance than paper straws and avoids additional adhesives. Owing to the 3D nanofiber network and strong interlayer connection, the comprehensive performance of this BC-based straw surpasses that of commercially available counterparts, satisfying the requirements for practical use. Of particular note, the edible character provides a better user experience and a new end-of-life option for the straws, making the BC-based straw a healthier and more eco-friendly substitute for plastic straws.
Developing biodegradable materials such as poly(lactic acid) (PLA) is a promising strategy to reduce the reliance on non-degradable plastics and the accumulation of those wastes. However, the fabrication of high-performance biodegradable films which integrate excellent mechanical and barrier properties remains a major challenge. To address this problem, the "brick and mortar" structure, one of the most effective biomimetic models, is introduced to improve the comprehensive properties of materials. Here, a PLA-assisted exfoliation and dispersion method to prepare the PLA coated mica nanosheets (Nano-mica/PLA) from a natural mineral phlogopite is presented. By introducing the sheer force assembly, a kind of nacre-inspired nanocomposite film with the "brick and mortar" structure can be fabricated. Such a nacre-inspired nanocomposite film shows excellent mechanical properties, UV-shielding, and gas barrier properties. The overall performance of the nacre-inspired nanocomposite film is superior to commercial plastic films, which will allow it possible to break a path for practical applications of PLA in the field of packaging.
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