Project description:Nanocrystalline carbon materials exhibit promising potential for sustainable and high-performance applications in electronics, energy storage, and environmental technologies. While sugars are abundant and renewable, converting them to graphitic carbon usually requires high temperature treatment. Here, we present a groundbreaking approach for synthesizing nanocrystalline carbon from readily available sugars such as glucose, fructose, and sucrose at ambient pressure and temperature. This novel method involves electrochemical reduction on a negatively charged Ag surface coupled with intermolecular dehydration between the organic precursors. By applying relatively low potentials ranging from -1.2 to -1.6 V vs. Ag/AgCl, and with the presence of hydrogen peroxide, oxygenic carbon precursors are efficiently transformed into nanocrystalline hybrid carbon structures. The role of hydrogen peroxide is pivotal in expediting hydrogen abstraction and facilitating the formation of 3D-nanostructured carbon allotropes. Characterization results based on Raman spectroscopy, transmission electron microscopy-energy dispersive X-ray spectroscopy-selected area electron diffraction (TEM-EDX-SAED), X-ray photoelectron spectroscopy (XPS), and grazing incidence-X-ray diffraction (GI-XRD) confirm the presence of mixed nanocrystalline sp2-sp3 hybridization in the resulting carbon materials. Moreover, this method's versatility extends beyond sugars to include alcohols, polyols, and polyphenolic compounds like ethanol, glycerol, and tannic acid, broadening its potential for biomass valorization.
Project description:Three-dimensional (3D) laser micro- and nanoprinting has become a versatile, reliable, and commercially available technology for the preparation of complex 3D architectures for diverse applications. However, the vast majority of structures published so far have been composed of only a single constituent material. Here, we present a system based on a microfluidic chamber integrated into a state-of-the-art laser lithography apparatus. This system is scalable in terms of the number of materials and eliminates the need to go back and forth between the lithography instrument and the chemistry room numerous times, with tedious realignment steps in between. As an application, we present 3D deterministic microstructured security features requiring seven different liquids: a nonfluorescent photoresist as backbone, two photoresists containing different fluorescent quantum dots, two photoresists with different fluorescent dyes, and two developers. Our integrated microfluidic 3D printing system opens the door to truly multimaterial 3D additive manufacturing on the micro- and nanoscale.
Project description:Carbon dots (CDs) with a room temperature phosphorescent (RTP) feature have attracted considerable interest in recent years due to their fundamental importance and promising applications. However, the reported matrix-free RTP CDs only show short-wavelength (green to yellow) emissions and have to be triggered by ultraviolet (UV) light (below 400 nm), limiting their applications in certain fields. Herein, visible-light-excited matrix-free RTP CDs (named AA-CDs) with a long-wavelength (orange) emission are reported for the first time. The AA-CDs can be facilely prepared via a microwave heating treatment of L-aspartic acid (AA) in the presence of ammonia and they emit unique orange RTP in the solid state with visible light (420 nm) excitation just being switched off. Through the studies of the carbonization process, the C=O and C=N containing moieties in the AA-CDs are confirmed to be responsible for the observed RTP emission. Finally, the applications of AA-CDs in information encryption and anti-counterfeiting were preliminarily demonstrated.
Project description:Wireless magnetic microrobots are envisioned to revolutionize minimally invasive medicine. While many promising medical magnetic microrobots are proposed, the ones using hard magnetic materials are not mostly biocompatible, and the ones using biocompatible soft magnetic nanoparticles are magnetically very weak and, therefore, difficult to actuate. Thus, biocompatible hard magnetic micro/nanomaterials are essential toward easy-to-actuate and clinically viable 3D medical microrobots. To fill such crucial gap, this study proposes ferromagnetic and biocompatible iron platinum (FePt) nanoparticle-based 3D microprinting of microrobots using the two-photon polymerization technique. A modified one-pot synthesis method is presented for producing FePt nanoparticles in large volumes and 3D printing of helical microswimmers made from biocompatible trimethy- lolpropane ethoxylate triacrylate (PETA) polymer with embedded FePt nanoparticles. The 30 μm long helical magnetic microswimmers are able to swim at speeds of over five body lengths per second at 200 Hz, making them the fastest helical swimmer in the tens of micrometer length scale at the corresponding low- magnitude actuation fields of 5-10 mT. It is also experimentally in vitro verified that the synthesized FePt nanoparticles are biocompatible. Thus, such 3D-printed microrobots are biocompatible and easy to actuate toward creating clinically viable future medical microrobots.
Project description:Silicones find use in a myriad of applications from sealants and adhesives to cooking utensils and medical implants. However, state-of-the-art silicone parts fall short in terms of shape complexity and reprocessability. Advances in three-dimensional printing and the discovery of vitrimers have recently opened opportunities for shaping and recycling of silicone objects. Here, we report the 3D printing via direct ink writing of silicone vitrimers into complex-shaped parts with high strength and room-temperature reprocessability. The reprocessing properties of the printed objects result from the adaptive nature of the silicone vitrimer, which can deform under stress without losing its network connectivity. Rheological and mechanical experiments reveal that printable inks can be tuned to generate strong parts with high creep resistance and room-temperature reprocessability, two properties that are usually challenging to reconcile in vitrimers. By combining printability, high strength, and room-temperature reprocessability, the reported silicone vitrimers represent an attractive sustainable alternative to currently available elastomers in a broad range of established and prospective applications.
Project description:Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.
Project description:In the field of surface synthesis, various reactions driven by the catalytic effect of metal substrates, particularly the Ullmann reaction, have been thoroughly investigated. The Wurtz reaction facilitates the coupling of alkyl halides through the removal of halogen atoms with a low energy barrier on the surface; however, the preparation of novel carbon nanostructures via the Wurtz reaction has been scarcely reported. Here, we report the successful synthesis of ethyl-bridged binaphthyl molecular chains on Ag(111) at room temperature via the Wurtz reaction. However, this structure was not obtained through low-temperature deposition followed by annealing even above room temperature. High-resolution scanning tunneling microscopy combined with density functional theory calculations reveal that the rate-limiting step of C-C homocoupling exhibits a low-energy barrier, facilitating the room-temperature synthesis of carbon nanochain structures. Moreover, the stereochemical configuration of adsorbed molecules hinders the activation of the C-X (X = Br) bond away from the metal surface and, therefore, critically influences the reaction pathways and final products. This work advances the understanding of surface-mediated reactions involving precursor molecules with stereochemical structures. Moreover, it provides an optimized approach for synthesizing novel carbon nanostructures under mild conditions.
Project description:C-H activation of methane followed by dehydrocoupling at room temperature led ultimately to the formation of the olefin H2C[double bond, length as m-dash]CH t Bu via the addition of redox-active ligands (L) such as thioxanthone or 2,2'-bipyridine (bipy) to (PNP)Ti[double bond, length as m-dash]CH t Bu(CH3) (1). Using both of these exogenous ligand systems, we could trap the titanium fragment via an insertion reaction with these two substrates to afford species of the type (PNP)Ti(L)(LH). A combination of computational and isotopic labeling studies reveals that the L ligand promotes the C-C bond forming step by migration of the methyl moiety in 1 to the α-alkylidene carbon by producing a Ti(iii) species (PNP)Ti{CH(CH3) t Bu}(L). In the case of L = thioxanthone, β-hydrogen abstraction gives an olefin, whereas with 2,2'-bipyridine β-hydride elimination and migratory insertion lead to (PNP)Ti(L)(LH). These redox-active ligands play two important roles: (i) they accept an electron from the Ti-alkylidene fragment to allow the methyl to approach the alkylidene and (ii) they serve as traps of a hydrogen atom resulting from olefin elimination. These systems represent the first homogeneous models that can activate methane and selectively dehydrocouple it with a carbene to produce an olefin at room temperature.
Project description:Super-soft elastomers derived from bottlebrush polymers show promise as advanced materials for biomimetic tissue and device applications, but current processing strategies are restricted to simple molding. Here, we introduce a design concept that enables the three-dimensional (3D) printing of super-soft and solvent-free bottlebrush elastomers at room temperature. The key advance is a class of inks comprising statistical bottlebrush polymers that self-assemble into well-ordered body-centered cubic sphere phases. These soft solids undergo sharp and reversible yielding at 20°C in response to shear with a yield stress that can be tuned by manipulating the length scale of microphase separation. The addition of a soluble photocrosslinker allows complete ultraviolet curing after extrusion to form super-soft elastomers with near-perfect recoverable elasticity well beyond the yield strain. These structure-property design rules create exciting opportunities to tailor the performance of 3D-printed elastomers in ways that are not possible with current materials and processes.
Project description:Room temperature magnetic ordering is reported for very small carbon dots (CDs), mat-like polyaniline nanofibers (Mat-PANI) and a composite of CDs@Mat-PANI containing 0.315 wt% CDs. We have found saturation magnetization (M S ) of CDs, Mat-PANI and CDs@Mat-PANI at 5 (20/300) K equals to 0.0079 (0.0048/0.0019), 0.0116 (0.0065/0.0055) and 0.0349 (0.0085/0.0077) emu/g, respectively. The M S enhancement in CDs@Mat-PANI (200% and 40% at 5 K and 300 K, respectively) is attributed to electron transfer from Mat-PANI imine N-atoms to the encapsulated CDs. Changes in M S values reveal that 0.81 (0.08) electron/CD is transferred at 5 (300) K, which is supported by observation of CDs photoluminescence (PL) redshift while in CDs@Mat-PANI. Band-bending and bandgap-renormalization calculations are used to predict a redshift of 117 meV at 300 K as a result of the electron transfer, in excellent agreement with the PL data (110 meV). Raman, X-ray diffraction and X-ray photoelectron spectroscopy data are used to confirm the electron transfer process as well as the strong interaction of CDs with PANI within CDs@Mat-PANI, which increases the crystalline domain size of Mat-PANI from about 4.8 nm to 9.2 nm while reducing the tensile strain from about 6.2% to 1.8%.