The engineering of biological molecules is a key concept in the design of highly functional, sophisticated soft materials. Biomolecules exhibit a wide range of functions and structures, including ...chemical recognition (of enzyme substrates or adhesive ligands
, for instance), exquisite nanostructures (composed of peptides
, proteins
or nucleic acids
), and unusual mechanical properties (such as silk-like strength
, stiffness
, viscoelasticity
and resiliency
). Here we combine the computational design of physical (noncovalent) interactions with pathway-dependent, hierarchical 'click' covalent assembly to produce hybrid synthetic peptide-based polymers. The nanometre-scale monomeric units of these polymers are homotetrameric, α-helical bundles of low-molecular-weight peptides. These bundled monomers, or 'bundlemers', can be designed to provide complete control of the stability, size and spatial display of chemical functionalities. The protein-like structure of the bundle allows precise positioning of covalent linkages between the ends of distinct bundlemers, resulting in polymers with interesting and controllable physical characteristics, such as rigid rods, semiflexible or kinked chains, and thermally responsive hydrogel networks. Chain stiffness can be controlled by varying only the linkage. Furthermore, by controlling the amino acid sequence along the bundlemer periphery, we use specific amino acid side chains, including non-natural 'click' chemistry functionalities, to conjugate moieties into a desired pattern, enabling the creation of a wide variety of hybrid nanomaterials.
Alkyl halide side groups are selectively incorporated into monodispersed, computationally designed coiled-coil-forming peptide nanoparticles. Poly2-(dimethylamino)ethyl methacrylate (PDMAEMA) is ...polymerized from the coiled-coil periphery using photoinitiated atom transfer radical polymerization (photoATRP) to synthesize well-defined, thermoresponsive star copolymer architectures. This facile synthetic route is readily extended to other monomers for a range of new complex star-polymer macromolecules.
Novel cobalt calixarene-capped and zirconium-based porous coordination cages were prepared with alkyne and azide functionality to leverage post-synthetic modification by click chemistry. While the ...calixarene-capped cages showed impressive stability when exposed to the most straightforward copper(
i
)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction conditions with copper(
ii
) sulfate and sodium ascorbate as the reducing agent, milder reaction conditions were necessary to perform analogous CuAAC reactions on zirconium-based cages. Reaction kinetics were monitored by IR spectroscopy, confirming rapid reaction times (<3 hours).
Novel cobalt calixarene-capped and zirconium-based porous coordination cages were prepared with alkyne and azide functionality to leverage post-synthetic modification by click chemistry.
Macrocyclization of linear peptides imparts improved stability to enzymatic degradation and increases potency of function. Many successful macrocyclization of peptides both in solution and on-resin ...have been achieved but are limited in scope as they lack selectivity, require long reaction times, or necessitate heat. To overcome these drawbacks a robust and facile strategy was developed employing thiol-Michael click chemistry via an N-methyl vinyl sulfonamide. We demonstrate its balance of reactivity and high stability through FTIR model kinetic studies, reaching 88% conversion over 30 min, and NMR stability studies, revealing no apparent degradation over an 8 day period in basic conditions. Using a commercially available reagent, 2-chloroethane sulfonyl chloride, the cell adhesion peptide, RGDS, was functionalized and macrocyclized on-resin with a relative efficiency of over 95%. The simplistic nature of this process demonstrates the effectiveness of vinyl sulfonamides as a thiol-Michael click acceptor and its applicability to many other bioconjugation applications.
Most studies of the mean-free path accumulation function (MFPAF) rely on optical techniques to probe heat transfer at length scales on the order of the phonon mean-free path. In this paper, we ...propose and implement a purely electrical probe of the MFPAF that relies on photo-lithographically defined heater-thermometer separation to set the length scale. An important advantage of the proposed technique is its insensitivity to the thermal interfacial impedance and its compatibility with a large array of temperature-controlled chambers that lack optical ports. Detailed analysis of the experimental data based on the enhanced Fourier law (EFL) demonstrates that heat-carrying phonons in gallium arsenide have a much wider mean-free path spectrum than originally thought.
Lanthanide monopnictide (Ln-V) nanoparticles embedded within III–V semiconductors, specifically in In0.53Ga0.47As, are interesting for thermoelectric applications. The electrical conductivity, ...Seebeck coefficient, and power factor of co-deposited TbAs:InGaAs over the temperature range of 300–700 K are reported. Using Boltzmann transport theory, it is shown that TbAs nanoparticles in InGaAs matrix give rise to an improved Seebeck coefficient due to an increase in scattering, such as ionized impurity scattering. TbAs nanoparticles act as electron donors in the InGaAs matrix while having minimal effects on electron mobility, and maintain high electrical conductivity. There is further evidence that TbAs nanoparticles act as energy dependent electron scattering sites, contributing to an increased Seebeck coefficient at high temperature. These results show that TbAs:InGaAs nanocomposite thinfilms containing low concentrations, specifically 0.78% TbAs:InGaAs, display high electrical conductivity, reduced thermal conductivity, improved Seebeck coefficient, and demonstrated ZT of power factors as high as 7.1 × 10-3 W K-2 m-1 and ZT as high as 1.6 at 650 K.
Lanthanide monopnictide (Ln‐V) nanoparticles embedded within III–V semiconductors, specifically in In0.53Ga0.47As, are interesting for thermoelectric applications. The electrical conductivity, ...Seebeck coefficient, and power factor of co‐deposited TbAs:InGaAs over the temperature range of 300–700 K are reported. Using Boltzmann transport theory, it is shown that TbAs nanoparticles in InGaAs matrix give rise to an improved Seebeck coefficient due to an increase in scattering, such as ionized impurity scattering. TbAs nanoparticles act as electron donors in the InGaAs matrix while having minimal effects on electron mobility, and maintain high electrical conductivity. There is further evidence that TbAs nanoparticles act as energy dependent electron scattering sites, contributing to an increased Seebeck coefficient at high temperature. These results show that TbAs:InGaAs nanocomposite thinfilms containing low concentrations, specifically 0.78% TbAs:InGaAs, display high electrical conductivity, reduced thermal conductivity, improved Seebeck coefficient, and demonstrated ZT of power factors as high as 7.1 × 10−3 W K−2 m−1 and ZT as high as 1.6 at 650 K.
TbAs:InGaAs has been demonstrated to be an excellent thermoelectric material at high temperatures, with ZT exceeding predictions from a theoretical model. This is likely due to an exceptional Seebeck coefficient, which is a result of energy dependent electron scattering by the band alignment from TbAs nanoparticles.
Most studies of the mean-free path accumulation function (MFPAF) rely on optical techniques to probe heat transfer at length scales on the order of the phonon mean-free path. In this paper, we ...propose and implement a purely electrical probe of the MFPAF that relies on photo-lithographically defined heater-thermometer separation to set the length scale. An important advantage of the proposed technique is its insensitivity to the thermal interfacial impedance and its compatibility with a large array of temperature-controlled chambers that lack optical ports. Detailed analysis of the experimental data based on the enhanced Fourier law (EFL) demonstrates that heat-carrying phonons in gallium arsenide have a much wider mean-free path spectrum than originally thought.
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