Project description:A low interfacial contact resistance is a challenge in polymer nanocomposites based on conductive nanomaterials for high-performance wearable electrode applications. Herein, a polydimethylsiloxane (PDMS)-based flexible nanocomposite incorporating high-conductivity 1D single-walled carbon nanotubes (SWCNTs) and 2D reduced graphene oxide (r-GO) was developed for high-performance electrocardiogram (ECG) wearable electrodes. A PDMS-SWCNT (P-SW; type I) nanocomposite containing only SWCNTs (2 wt%), exhibited rough and non-uniform surface morphology owing to the strong bundling effect of as-grown SWCNTs and randomly entangled aggregate structures and because of inefficient vacuum degassing (i.e., R P-SW = 1871 Ω). In contrast, owing to the hybrid structure of the SWCNTs (1 wt%) and r-GO (1 wt%), the PDMS-SWCNTs/r-GO (P-SW/r-GO; type II) nanocomposite exhibited uniform surface characteristics and low contact resistance (i.e., R P-SW/r-GO = 63 Ω) through the formation of hybrid and long conducting pathways. The optimized nanocomposite (P-SW/r-GO/f; type III) possessed a fabric-assisted structure that enabled tunable and efficient vacuum degassing and curing conditions. Additionally, a long and wide conducting pathway was formed through more uniform and dense interconnected structures, and the contact resistance was drastically reduced (i.e., R P-SW/r-GO/f = 15 Ω). The performance of the electrodes fabricated using the optimized nanocomposites was the same or higher than that of commercial Ag/AgCl gel electrodes during real-time measurement for ECG Bluetooth monitoring. The developed high-performance hybrid conducting polymer electrodes are expected to contribute significantly to the expansion of the application scope of wearable electronic devices and wireless personal health monitoring systems.
Project description:Nanoparticles of the 1D and 2D coordination polymers [Zn(OAc)2(bipy)] n and [Zn(TFA)2(bppa)2] n were prepared, employing polystyrene-block-poly(4-vinylpyridine) diblock copolymers with different weight fractions of the 4-vinylpyridine (4VP) block and comparable overall molecular weights of M n ≈ 155 kg mol-1 as template (SV-15 and SV-42 with 15 and 42 wt% 4VP, respectively). [Zn(OAc)2(bipy)] n nanoparticles were successfully synthesised within the 4VP core of SV-42 micelles, showing a core size of D core = 47 ± 5 nm and a hydrodynamic diameter of D h = 157 ± 46 nm, determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The crystallinity of the composite is quite low, showing only low intensity reflexes in the powder X-ray diffraction (PXRD) pattern with the highest particle load. No indications for larger microcrystals were detected by scanning electron microscopy (SEM), proving the successful integration of the coordination polymer nanoparticles within the micellar cores. Nanocomposites of the 2D coordination network [Zn(TFA)2(bppa)2] n were synthesised using both diblock copolymers. The particle core sizes (from TEM) and hydrodynamic diameters (from DLS) correlate with the 4VP fraction of the micelles, resulting in D core = 46 ± 6 nm for SV-42 and 15 ± 2 nm for SV-15 and D h = 340 ± 153 nm and 177 ± 57 nm, respectively. The successful synthesis was proven by PXRD and SEM images, confirming the absence of larger crystallites. Hence, it is possible to synthesise nanocomposites of Zn-based 1D and 2D coordination polymers by a direct approach utilizing diblock copolymer micelles as template.
Project description:Bifunctional hairy silica nanoparticles (BHSNs), which are silica nanoparticles covered with alkyl and amino organic chains, were prepared as high-performance additives for lubricants. Compared with hairy silica nanoparticles covered by a single type of organic chain, binary hairy silica nanoparticles exhibit the advantages of both types of organic chains, which exhibit excellent compatibility with lubricants and adsorbability to metal surfaces. Nanoparticles with different ratios of amino and alkyl ligands were investigated. In comparison to an untreated lubricant, BHSNs reduce the friction coefficient and wear scar diameter by 40% and 60%, respectively. The wear mechanism of BHSNs was investigated, and the protective and filling effect of the nanoparticles improved because of collaboration of amino and alkyl ligands.
Project description:Goldbeating is the ancient craft of thinning bulk gold (Au) into gossamer leaves. Pioneered by ancient Egyptian craftsmen, modern mechanized iterations of this technique can fabricate sheets as thin as ∼100 nm. We take inspiration from this millennia-old craft and adapt it to the nanoscale regime, using colloidally synthesized 0D/1D Au nanoparticles (AuNPs) as highly ductile and malleable nanoscopic Au ingots and subjecting them to solid-state, uniaxial compression. The applied stress induces anisotropic morphological transformation of AuNPs into 2D leaf form and elucidates insights into metal nanocrystal deformation at the extreme length scales. The induced 2D morphology is found to be dependent on the precursor 0D/1D NP morphology, size (0D nanosphere diameter and 1D nanorod diameter and length), and their on-substrate arrangement (e.g., interparticle separation and packing order) prior to compression. Overall, this versatile and generalizable solid-state compression technique enables new pathways to synthesize and investigate the anisotropic morphological transformation of arbitrary NPs and their resultant emergent phenomena.
Project description:The pH-controlled M2 protein from influenza A is a critical component of the virus and serves as a target for the aminoadamantane antiflu agents that block its H+ channel activity. To better understand its H+ gating mechanism, we investigated M2 in lipid bilayers with a new combination of IR spectroscopies and theory. Linear Fourier transform infrared (FTIR) spectroscopy was used to measure the precise orientation of the backbone carbonyl groups, and 2D infrared (IR) spectroscopy was used to identify channel-lining residues. At low pH (open state), our results match previously published solid-state NMR and X-ray structures remarkably well. However, at neutral pH when the channel is closed, our measurements indicate that a large conformational change occurs that is consistent with the transmembrane alpha-helices rotating by one amino acid register--a structural rearrangement not previously observed. The combination of simulations and isotope-labeled FTIR and 2D IR spectroscopies provides a noninvasive means of interrogating the structures of membrane proteins in general and ion channels in particular.
Project description:Asymmetric supercapacitors (ASCs) have attracted widespread attention because of their high energy density, high power density and long cycle life. Nevertheless, the development of anodes and cathodes with complementary potential windows and synchronous energy storage kinetics represents a pivotal challenge. We propose to construct nanochannel-coupled vertically porous CNF/Ti3CNTx and CNF/rGO hybrid aerogel electrodes via a unidirectional bottom-up cryoprocess. The vertically porous structure will greatly shorten the ion diffusion path and enhance the charge/ion transfer/diffusion kinetics, and the inserted cellulose nanofibers (CNFs) will impede the re-stacking of the nanosheets and enlarge the interlayer nano-channels, thus improving the accessibility of electrolyte ions. Ultimately, all-solid-state ASCs assembled based on nanochannel-coupled vertically porous MXene and graphene aerogel can achieve an excellent energy density of 20.8 Wh kg-1 at 2.3 kW·kg-1, a high multiplicity performance, and retains 95.1% of energy density after 10,000 cycles. This work not only demonstrates the great superiority of nanochannel-coupled vertically porous hybrid aerogels, but also provides an effective strategy for designing asymmetric supercapacitor electrodes with matched structural and electrochemical properties.
Project description:Surface plasmon-polariton (SPP) excitations of metal-dielectric interfaces are a fundamental light-matter interaction which has attracted interest as a route to spatial confinement of light far beyond that offered by conventional dielectric optical devices. Conventionally, SPPs have been studied in noble-metal structures, where the SPPs are intrinsically bound to a 2D metal-dielectric interface. Meanwhile, recent advances in the growth of hybrid 2D crystals, which comprise laterally connected domains of distinct atomically thin materials, provide the first realistic platform on which a 2D metal-dielectric system with a truly 1D metal-dielectric interface can be achieved. Here we show for the first time that 1D metal-dielectric interfaces support a fundamental 1D plasmonic mode (1DSPP) which exhibits cutoff behavior that provides dramatically improved light confinement in 2D systems. The 1DSPP constitutes a new basic category of plasmon as the missing 1D member of the plasmon family: 3D bulk plasmon, 2DSPP, 1DSPP, and 0D localized SP.
Project description:Understanding how cells migrate in fibrous environments is important in wound healing, immune function, and cancer progression. A key question is how fiber orientation and network geometry influence cell movement. Here we describe a quantitative, modeling-based approach toward identifying the mechanisms by which cells migrate in fibrous geometries having well controlled orientation. Specifically, U251 glioblastoma cells were seeded onto non-electrospinning Spinneret based tunable engineering parameters fiber substrates that consist of networks of suspended 400 nm diameter nanofibers. Cells were classified based on the local fiber geometry and cell migration dynamics observed by light microscopy. Cells were found in three distinct geometries: adhering two a single fiber, adhering to two parallel fibers, and adhering to a network of orthogonal fibers. Cells adhering to a single fiber or two parallel fibers can only move in one dimension along the fiber axis, whereas cells on a network of orthogonal fibers can move in two dimensions. We found that cells move faster and more persistently in 1D geometries than in 2D, with cell migration being faster on parallel fibers than on single fibers. To explain these behaviors mechanistically, we simulated cell migration in the three different geometries using a motor-clutch based model for cell traction forces. Using nearly identical parameter sets for each of the three cases, we found that the simulated cells naturally replicated the reduced migration in 2D relative to 1D geometries. In addition, the modestly faster 1D migration on parallel fibers relative to single fibers was captured using a correspondingly modest increase in the number of clutches to reflect increased surface area of adhesion on parallel fibers. Overall, the integrated modeling and experimental analysis shows that cell migration in response to varying fibrous geometries can be explained by a simple mechanical readout of geometry via a motor-clutch mechanism.
Project description:In this study, cobalt ferrites (C) decorated onto 2D material (porous graphene (PG)) and 1D material (carbon nanofibers (CNF)), denoted as PG-C and CNF-C nanocomposites, respectively, were synthesized using solvothermal process. The prepared nanocomposites were studied as magnetic adsorbents for the removal of lead (cationic) and chromium(VI) (anionic) metal ions. The structural and chemical analysis of synthesized nanocomposites was conducted using different characterization techniques including Brunauer-Emmett-Teller (BET) analysis, field emission-scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), high resolution-transmission electron microscopy (HR-TEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Batch mode adsorption studies were conducted with the prepared nanocomposites to examine their maximum adsorption potential for lead and chromate ions. Performance parameters (time, pH, adsorbent dosage and initial ion concentrations) effecting the adsorption capacity of the nanocomposites were optimized. Different kinetic and isotherm models were examined to elucidate the adsorption process. Synthesized nanocomposites exhibited significant potential for the studied metal ions that can be further examined at pilot scale for the removal of metal ions from contaminated water.
Project description:Strain engineering is a powerful tool in designing artificial platforms for high-temperature excitonic quantum devices. Combining strong light-matter interaction with robust and mobile exciton quasiparticles, two-dimensional transition metal dichalcogenides (2D TMDCs) hold great promise in this endeavor. However, realizing complex excitonic architectures based on strain-induced electronic potentials alone has proven to be exceptionally difficult so far. Here, we demonstrate deterministic strain engineering of both single-particle electronic bandstructure and excitonic many-particle interactions. We create quasi-1D transport channels to confine excitons and simultaneously enhance their mobility through locally suppressed exciton-phonon scattering. Using ultrafast, all-optical injection and time-resolved readout, we realize highly directional exciton flow with up to 100% anisotropy both at cryogenic and room temperatures. The demonstrated fundamental modification of the exciton transport properties in a deterministically strained 2D material with effectively tunable dimensionality has broad implications for both basic solid-state science and emerging technologies.