199 research outputs found
Tuning the Chiral Structures from Self‐Assembled Carbohydrate Derivatives
No full textCarbohydrates have been regarded as one of the most ideally suited candidates for chirality study via self-assembly owning to their unique chemical structures, abundance, and sustainability. Much efforts have been devoted to design and synthesize diverse carbohydrate derivatives and self-assemble them into various supermolecular morphologies. Nevertheless, still inadequate attention is paid to deeply and comprehensively understand how the carbohydrate structures and self-assembly approaches affect the final morphologies and properties for future demands. Herein, to fulfill the need, a range of recently published studies relating to the chirality of carbohydrates is reviewed and discussed. Furthermore, to tune the chirality of carbohydrate-based structures on both molecular and superstructural levels via chirality transfer and chirality expression, the designing of the molecules and choosing of the proper approaches for self-assembly are elucidated.China Scholarship Council http://dx.doi.org/10.13039/50110000454
Self‐Assembled Heterosymmetric Structure with Tunable Polarization Optics for Reversible Matrix Encryption
No full textAbstract Symmetric and asymmetric structures are generally taken as contradictory structures. Developing novel hierarchical self‐assembled structures by harmonically combining both symmetry and asymmetry, which we termed “heterosymmetric structures”, along with quantitative analysis of their formation process, remains underexplored but is crucial for advancing science and applications. Herein, we create novel heterosymmetric architectures using sustainable colloidal nanoparticles, cellulose nanocrystals (CNC), and hydrophilic nanolignin (NL), by modulating their evaporation kinetics and deposition behaviors to fabricate heterosymmetric films with tunable polarized optical properties for time‐dependent reversible matrix encryption. During drying, the increased concentration within CNC/NL colloidal droplets and the liquid crystal phase separation induced by CNC regulate the dynamic competition between Marangoni and capillary flows. Erickson number quantifies the influence of liquid crystal elasticity and viscous forces at the triple‐phase contact line in heterosymmetric structure formation. The unique heterosymmetric nature of the resulting films imparts a cross‐extinction pattern accompanied by strong birefringence, circular dichroism, circularly polarized luminescence with high luminescence asymmetry factor up to 0.6 and dynamic solvent responsiveness, enabling successful multilevel encryption applications. The insights in this study not only expand the knowledge of symmetric/asymmetric structures but also enhance understanding of collective behaviors in non‐equilibrium systems for self‐assembling various hierarchical structures with promising properties.China Scholarship Council https://doi.org/10.13039/501100004543Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659Niedersächsische Ministerium für Wissenschaft und Kultur https://doi.org/10.13039/10001193
Enhanced water evaporation via coupled capillary transport and gelation in confined nanocrystal systems
No full textDrying in confined systems is a critical process with broad implications, spanning applications from materials science to water management in microscale technologies. Nevertheless, the coupled dynamics of transport and gelation in confined drying of colloidal suspensions remains poorly understood. Here cellulose nanocrystals (CNCs) are employed as a model system to systematically investigate the temporal dynamics, kinetic behavior, and structural transformation of nanocrystal suspensions during capillary drying. We report a mechanism whereby CNC suspensions, upon exceeding a critical concentration (∼1 wt%), undergo a transition from a fluid-like state to a kinetically arrested gel state at the evaporation front. This transition is accompanied by pinning of the evaporation interface at the capillary opening and leads to the formation of a gel–film heterostructure, consisting of a CNC gel layer with a water concentration gradient and a thin surface film formed via interfacial slip. This heterostructure promotes directional water transport from the capillary interior to the interface and significantly enhances the effective evaporative area, thereby accelerating the overall drying process. These findings offer insights into confinement-driven drying behavior and establish a framework for regulating evaporation kinetics in colloidal systems.Emory University http://dx.doi.org/10.13039/100006939Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659China Scholarship Council http://dx.doi.org/10.13039/50110000454
Dehydration regulates structural reorganization of dynamic hydrogels
No full textAbstract The dehydration process is widely recognized as a significant phenomenon in nature. Hydrogels, which are important functional materials with high water content and crosslinked networks, encounter the issue of dehydration in their practical applications. Here, we report the distinctive anisotropic dehydration modality of dynamic hydrogels, which is fundamentally different from the more commonly observed isotropic dehydration of covalent hydrogels. Xerogels derived from dynamic hydrogel dehydration will fully cover a curved substrate surface and exhibit hollow structures with internal knots, in contrast to the bulk xerogels produced by covalent hydrogel dehydration. Depending on the competing cohesion of polymer chains and the adhesion at the hydrogel-substrate interface, the previously overlooked reorganization of polymer networks within dynamic hydrogels, triggered by dehydration-induced stress, has been discovered to regulate such macroscopic structural reconstruction for dynamic hydrogel dehydration. With the attached hydrogel-substrate interface, the surface microstructures of substrates can also be engraved onto xerogels with high resolution and on a large scale. This work will greatly enhance our understanding of the soft matter dehydration process and broaden the applications of dehydration technologies using water-containing materials.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659Niedersächsisches Ministerium für Wissenschaft und Kultur https://doi.org/10.13039/501100010570China Scholarship Council https://doi.org/10.13039/501100004543Open-Access-Publikationsfonds 202
Solvothermal engineering of lignin-based fluorescent/phosphorescent carbon dots with tunable multicolor emission
No full texthttp://dx.doi.org/10.13039/501100001809 National Natural Science Foundation of Chinahttp://dx.doi.org/10.13039/501100007129 Natural Science Foundation of Shandong Provincehttp://dx.doi.org/10.13039/501100000038 Natural Sciences and Engineering Research Council of Canadahttp://dx.doi.org/10.13039/501100004543 China Scholarship Councilhttp://dx.doi.org/10.13039/100005156 Alexander von Humboldt-Stiftun
Scale‐Spanning Strong Adhesion Using Cellulose‐Based Microgels
No full textAdhesive gels derived from biobased sustainable materials have extremely broad application prospects, such as in flexible smart materials and biomedicine fields. Combining high toughness and strong, persisting repeatable adhesion has always been a daunting challenge for adhesive gels. However, bulk gels based on polysaccharides as the most abundant bio-based compounds usually possess a high toughness but weak interfacial adhesion due to the strong hydration potential. Herein, a novel kind of highly tough microgel membranes with rough surfaces is fabricated using loosely chemically cross-linked dihydroxypropyl cellulose (cDHPC) microgels (average size = 1.25 ± 0.03 µm). Such microgel membranes exhibit strong, instant, and persisting adhesion to various substrates with different surface roughness. Slight chemical cross-linking and multiple physical interactions within microgels and resulting microgel membranes lead to high tensile strength and toughness of 0.23 ± 0.03 MPa and 73.8 ± 9.3 KJ m-3 , respectively. The maximum adhesive strength and debonding work exceed 320 ± 0.50 KPa and 160.97 ± 0.20 J m-2 , respectively. After five cycles (re-lap after detaching), the adhesive strength still remains above 200 KPa. Their adhesive properties outperform most bio-based adhesive gels and even petroleum-based gels, which are based on synergistic molecular and microscaled topological interactions
‐Glucosamine for the Preparation of Imidazo[1,5‐a]pyridines
No full textThe targeted cleavage of the C−N bonds of alkyl primary amines in sustainable compounds of biomass according to a metal‐free pathway and the conjunction of nitrogen in the synthesis of imidazo[1,5‐a]pyridines are still highly challenging. Despite tremendous progress in the synthesis of imidazo[1,5‐a]pyridines over the past decade, many of them can still not be efficiently prepared. Herein, we report an anomeric stereoauxiliary approach for the synthesis of a wide range of imidazo[1,5‐a]pyridines after cleaving the C−N bond of d‐glucosamine (α‐2° amine) from biobased resources. This new approach expands the scope of readily accessible imidazo[1,5‐a]pyridines relative to existing state‐of‐the‐art methods. A key strategic advantage of this approach is that the α‐anomer of d‐glucosamine enables C−N bond cleavage via a seven‐membered ring transition state. By using this novel method, a series of imidazo[1,5‐a]pyridine derivatives (>80 examples) was synthesized from pyridine ketones (including para‐dipyridine ketone) and aldehydes (including para‐dialdehyde). Imidazo[1,5‐a]pyridine derivatives containing diverse important deuterated C(sp(2))−H and C(sp(3))−H bonds were also efficiently achieved
Electrospun Lignin/ZnO Nanofibrous Membranes for Self‐Powered Ultrasensitive Flexible Airflow Sensor and Wearable Device
No full textAbstract The interest and demand for flexible sensors and wearable devices are rapidly growing. The added benefit of electricity generation, enabling gas sensors to be self‐powered, increases the applicability of these devices for flexible and wearable airflow sensors. Inspired by water evaporation‐induced power generation, this study explores its potential in sensing applications, which has not yet been explored in detail. Electrospinning technology is used to prepare superhydrophilic lignin/ZnO nanofibrous membranes with a ZnO nanoparticle layer, capable of generating at least 100 mV (which allows it to power its own signal transduction). The membrane is highly sensitive to variations in airflow, enabling its use as an ultrasensitive and flexible airflow sensor. This sensor demonstrates exceptional performance, including a fast response time (0.65 s), broad detection range (with lower detection limit down to 0.25 and upper detection limit of 3 m s −1 ), and extremely high airflow velocity detection accuracy. Beyond these, it can serve as a wearable sensor for sweat monitoring, motion detection, and breath monitoring (to accurately detect breathing rate, intensity and variations in speech). Such self‐powered, ultrasensitive, and flexible lignin/ZnO airflow sensors provide novel potential to advance the development of smart textiles and wearable electronics.Natural Sciences and Engineering Research Council of Canada https://doi.org/10.13039/501100000038Alexander von Humboldt-Stiftung https://doi.org/10.13039/100005156Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Amorphous–Crystalline Solid Transformation-Induced Self-Actuation of Bending-to-Straightening Behavior via Helical Deformation
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