Water‐Rich Biomimetic Composites with Abiotic Self‐Organizing Nanofiber Network

Load‐bearing soft tissues, e.g., cartilage, ligaments, and blood vessels, are made predominantly from water (65–90%) which is essential for nutrient transport to cells. Yet, they display amazing stiffness, toughness, strength, and deformability attributed to the reconfigurable 3D network from stiff collagen nanofibers and flexible proteoglycans. Existing hydrogels and composites partially achieve some of the mechanical properties of natural soft tissues, but at the expense of water content. Concurrently, water‐rich biomedical polymers are elastic but weak. Here, biomimetic composites from aramid nanofibers interlaced with poly(vinyl alcohol), with water contents of as high as 70–92%, are reported. With tensile moduli of ≈9.1 MPa, ultimate tensile strains of ≈325%, compressive strengths of ≈26 MPa, and fracture toughness of as high as ≈9200 J m−2, their mechanical properties match or exceed those of prototype tissues, e.g., cartilage. Furthermore, with reconfigurable, noncovalent interactions at nanomaterial interfaces, the composite nanofiber network can adapt itself under stress, enabling abiotic soft tissue with multiscale self‐organization for effective load bearing and energy dissipation.Water‐rich biomimetic composites from aramid nanofibers interlaced with poly(vinyl alcohol) emulate the collagen–proteoglycan network in load‐bearing soft tissues. The hydrogen bonding between stiff nanofibers and soft polymers affords synergistic stiffening and toughening, allowing the nanofiber network to self‐organize under stress for effective load bearing and energy dissipation. Their mechanics, biocompatibility, and high water content permit utilization as load‐bearing biomaterials and for other applications including durable high‐transport‐rate membranes, membranes in water desalination, fuel cells, and batteries.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141174/1/adma201703343-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141174/2/adma201703343_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141174/3/adma201703343.pd

Materials science: Carbon sheet solutions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62936/1/442254a.pd

Monte Carlo simulation of linear aggregate formation from CdTe nanoparticles

In recent works it was found that nanometre sized particles of CdTe could spontaneously reorganize into crystalline nanowires (NWs) upon controlled removal of the protecting shell of organic stabilizer in an aqueous medium. At present, there is no possibility of predicting for certain the outcome of each particular NW self-assembly experiment or influencing the geometric parameters of the aggregates. A model for the simulation of the interaction of CdTe nanoparticles (NPs) and their aggregation into clusters has been developed and a Monte Carlo simulation was performed. A ‘linearity coefficient’ has been developed and introduced into the model that allows for the comparison of NP aggregate geometries and investigation of the dependence of aggregate shapes on NP charge and dipole strength. The simulation results show that the presence of a dipole moment is crucial to the formation of chain-like NP aggregates. The shapes of the clusters that were obtained during simulations resemble those seen in the experiment, although serious differences are still observed, which hint at the influence of other, most probably, short-range interparticle forces on the clustering process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49086/2/msmse5_3_008.pd

Chiral templating of self-assembling nanostructures by circularly polarized light

PMCID: PMC4387888.-- et al.The high optical and chemical activity of nanoparticles (NPs) signifies the possibility of converting the spin angular momenta of photons into structural changes in matter. Here, we demonstrate that illumination of dispersions of racemic CdTe NPs with right- (left-)handed circularly polarized light (CPL) induces the formation of right- (left-)handed twisted nanoribbons with an enantiomeric excess exceeding 30%, which is â 1/410 times higher than that of typical CPL-induced reactions. Linearly polarized light or dark conditions led instead to straight nanoribbons. CPL templating of NP assemblies is based on the enantio-selective photoactivation of chiral NPs and clusters, followed by their photooxidation and self-assembly into nanoribbons with specific helicity as a result of chirality-sensitive interactions between the NPs. The ability of NPs to retain the polarization information of incident photons should open pathways for the synthesis of chiral photonic materials and allow a better understanding of the origins of biomolecular homochirality.This material is based on work partially supported by the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under award number #DE-SC0000957, and by ARO MURI W911NF-12-1-0407 ‘Coherent Effects in Hybrid Nanostructures for Lineshape Engineering of Electromagnetic Media’ (N.A.K. and S.L.). We acknowledge support from the NSF under grant ECS-0601345; CBET 0933384; CBET 0932823; and CBET 1036672. Financial support from the Robert A. Welch Foundation (C-1664) is also acknowledged (S.L.). Support from the NIH grant GM085043 (P.Z.) is gratefully acknowledged. The work of P.K. was supported by the NSF DMR grant No. 1309765 and by the ACS PRF grant No. 53062-ND6.Peer Reviewe

Synthesis and bioevaluation of 125 I-labeled gold nanorods

A novel technique is described for monitoring the in vivo behavior of gold nanorods (GNRs) using _-imaging. GNRs were radiolabeled using [ 125 I] sodium iodide in a simple and fast manner with high yield and without disturbing their optical properties. Radiolabeled GNRs were successfully visualized by radioisotope tagging, allowing longitudinal in vivo studies to be performed repeatedly in the same animal. The preliminary biodistribution study showed that PEGylated GNRs have much longer blood circulation times and clear out faster, while bare GNRs accumulate quickly in the liver after systematic administration. The highly efficient method reported here provides an extensively useful tool for guidance of the design and development of new gold nanoparticles as target-specific agents for both diagnostics and photothermal therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90787/1/0957-4484_22_13_135102.pd

Self‐Assembly Mechanism of Spiky Magnetoplasmonic Supraparticles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106774/1/adfm201302405.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106774/2/adfm201302405-sup-0001-S1.pd

Diverse Nanoassemblies of Graphene Quantum Dots and Their Mineralogical Counterparts

Complex structures from nanoparticles are found in rocks, soils, and sea sediments but the mechanisms of their formation are poorly understood, which causes controversial conclusions about their genesis. Here we show that graphene quantum dots (GQDs) can assemble into complex structures driven by coordination interactions with metal ions commonly present in environment and serve a special role in Earth’s history, such as Fe3+ and Al3+. GQDs self- assemble into mesoscale chains, sheets, supraparticles, nanoshells, and nanostars. Specific assembly patterns are determined by the effective symmetry of the GQDs when forming the coordination assemblies with the metal ions. As such, maximization of the electronic delocalization of Ï - orbitals of GQDs with Fe3+ leads to GQD- Fe- GQD units with D2 symmetry, dipolar bonding potential, and linear assemblies. Taking advantage of high electron microscopy contrast of carbonaceous nanostructures in respect to ceramic background, the mineralogical counterparts of GQD assemblies are found in mineraloid shungite. These findings provide insight into nanoparticle dynamics during the rock formation that can lead to mineralized structures of unexpectedly high complexity.Complex structures from nanoparticles are found in rocks, soils, and sea sediments but the mechanisms of their formation are poorly understood. It is shown that graphene quantum dots (GQDs) can assemble into complex structures driven by coordination interactions with metal ions commonly present in the environment and play a special role in Earth’s history, such as Fe3+ and Al3+.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155475/1/anie201908216_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155475/2/anie201908216.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155475/3/anie201908216-sup-0001-misc_information.pd

Diverse Nanoassemblies of Graphene Quantum Dots and Their Mineralogical Counterparts

Complex structures from nanoparticles are found in rocks, soils, and sea sediments but the mechanisms of their formation are poorly understood, which causes controversial conclusions about their genesis. Here we show that graphene quantum dots (GQDs) can assemble into complex structures driven by coordination interactions with metal ions commonly present in environment and serve a special role in Earth’s history, such as Fe3+ and Al3+. GQDs self- assemble into mesoscale chains, sheets, supraparticles, nanoshells, and nanostars. Specific assembly patterns are determined by the effective symmetry of the GQDs when forming the coordination assemblies with the metal ions. As such, maximization of the electronic delocalization of Ï - orbitals of GQDs with Fe3+ leads to GQD- Fe- GQD units with D2 symmetry, dipolar bonding potential, and linear assemblies. Taking advantage of high electron microscopy contrast of carbonaceous nanostructures in respect to ceramic background, the mineralogical counterparts of GQD assemblies are found in mineraloid shungite. These findings provide insight into nanoparticle dynamics during the rock formation that can lead to mineralized structures of unexpectedly high complexity.Komplexe Strukturen aus Nanopartikeln sind in Gesteinen, Böden und Meeressedimenten zu finden, aber die Mechanismen ihrer Entstehung sind kaum verstanden. Es wird gezeigt, dass sich Graphenquantenpunkte (GQDs) zu komplexen Strukturen zusammenfügen können, angetrieben durch Koordinationswechselwirkungen mit Metallionen wie Fe3+ and Al3+, die in der Umwelt häufig vorkommen und eine besondere Rolle in der Erdgeschichte spielen.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155470/1/ange201908216.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155470/2/ange201908216_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155470/3/ange201908216-sup-0001-misc_information.pd

Rapid aqueous photo-polymerization route to polymer and polymer-composite hydrogel 3D inverted colloidal crystal scaffolds

Successful regeneration of biological tissues in vitro requires the utilization of three-dimensional (3D) scaffolds that provide a near natural microenvironment for progenitor cells to grow, interact, replicate, and differentiate to form target tissues. In this work, a rapid aqueous photo-polymerization route was developed toward the fabrication of a variety of polymer hydrogel 3D inverted colloidal crystal (ICC) scaffolds having different physical and chemical properties. To demonstrate the versatility of this technique, a variety of polymer hydrogel ICC scaffolds were prepared, including (1) polyacrylamide (pAAM) scaffolds, (2) poly(2-hydroxyethyl methacrylate) (pHEMA) scaffolds, (3) poly(2-hydroxyethyl acrylate) (pHEA) scaffolds, and composite scaffolds including (4) pAAM-pHEMA scaffolds, (5) pHEMA-pMAETAC [poly(2-methacryloyloxy) trimethyl ammonium] scaffolds, and (6) pHEA-pMEATAC scaffolds. Templates for scaffolds incorporated both uniform sized (104 Μm diameter) and nonuniform sized (100 ± 20 Μm diameter) closely packed noncrosslinked poly(methyl methacrylate) beads. Human bone marrow stromal HS-5 cells were cultured on the six different types of scaffolds to demonstrate biocompatibility. Experimental results show that cells can remain viable in these scaffolds for at least 5 weeks. Of the six scaffolds, maximal cell adhesion and proliferation are obtained on the positively charged composite hydrogel pHEMA-pMEATAC and pHEA-pMAETAC scaffolds. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56168/1/31199_ftp.pd

Multifunctional layer-by-layer carbon nanotube–polyelectrolyte thin films for strain and corrosion sensing

Since the discovery of carbon nanotubes, researchers have been fascinated by their mechanical and electrical properties, as well as their versatility for a wide array of applications. In this study, a carbon nanotube–polyelectrolyte composite multilayer thin film fabricated by a layer-by-layer (LbL) method is proposed to develop a multifunctional material for measuring strain and corrosion processes. LbL fabrication of carbon nanotube composites yields mechanically strong thin films in which multiple sensing transduction mechanisms can be encoded. For example, judicious selection of carbon nanotube concentrations and polyelectrolyte matrices can yield thin films that exhibit changes in their electrical properties to strain and pH. In this study, experimental results suggest a consistent trend between carbon nanotube concentrations and strain sensor sensitivity. Furthermore, by simply altering the type of polyelectrolyte used, pH sensors of high sensitivity can be developed to potentially monitor environmental factors suggesting corrosion of metallic structural materials (e.g. steel, aluminum).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58148/2/sms7_2_022.pd