Pollen grains have the potential to be effective plant-based biorenewable reinforcing fillers for polymers due to their high mechanical strength, chemical stability, and unique micro- and ...nano-structured surfaces. Pollen-polymer composites could form the basis for a new class of light-weight, high strength sustainable materials if compatible polymer-filler systems can be engineered. The exine shell of pollen, composed of sporopollenin, offers opportunities for surface functionalization to provide for compatibility between the pollen and the polymer matrix, but this idea has been previously unexplored. We present the first demonstration of surface functionalization of sporopollenin to enable incorporation of pollen as a reinforcing filler, using ragweed pollen in poly(vinyl acetate) (PVAc). Composites prepared with 'as received', untreated ragweed pollen displayed interfacial voids, degraded mechanical properties, and a decreased glass transition width with increased pollen loading, relative to neat PVAc. Composites prepared with pollen treated viaan acid-base surface preparation displayed improved interfacial morphology and increasing modulus with pollen loading (29% increase). Interfacial adhesion was optimal for pollen functionalized with vinyltrimethoxysilane (VTMS), followed by in situfree radical polymerization of PVAc. In situpolymerization of functionalized pollen resulted in simultaneous stiffening and strengthening of composites (80% increase in tensile strength). Films containing treated and functionalized pollen also displayed a wider glass transition regions in the presence of pollen filler relative to neat PVAc.
A simple solution processed layer-by-layer approach was used to immobilize metal nanoparticles (NPs) on the surface of ragweed pollen exine to obtain multifunctional particles with significant ...surface-enhanced Raman scattering (SERS), two-photon excited fluorescence, and enhanced adhesion properties. The rugged pollen exine was functionalized with an amine terminated silane and then treated with Ag or Ag@SiO2 NPs that were electrostatically attached to the exterior of the pollen by incubation in an NP solution of the appropriate pH. Nanoparticle agglomeration on the pollen gives rise to broadband near infrared (NIR) (785–1064 nm) plasmonic activity, and strong SERS signals from benzenedithiol deposited on NP–pollen composite particles were observed. In addition to SERS activity, the AgNP coating provides a twofold increase in the adhesive properties of the RW pollen exine on a silicon substrate, leading to a robust, adhesive, broadband NIR excitable SERS microparticle.
A simple solution processed layer-by-layer approach was used to immobilize metal nanoparticles (NPs) on the surface of ragweed pollen exine to obtain multifunctional particles with significant ...surface-enhanced Raman scattering (SERS), two-photon excited fluorescence, and enhanced adhesion properties. The rugged pollen exine was functionalized with an amine terminated silane and then treated with Ag or Ag@SiO
NPs that were electrostatically attached to the exterior of the pollen by incubation in an NP solution of the appropriate pH. Nanoparticle agglomeration on the pollen gives rise to broadband near infrared (NIR) (785-1064 nm) plasmonic activity, and strong SERS signals from benzenedithiol deposited on NP-pollen composite particles were observed. In addition to SERS activity, the AgNP coating provides a twofold increase in the adhesive properties of the RW pollen exine on a silicon substrate, leading to a robust, adhesive, broadband NIR excitable SERS microparticle.
Adhesion through Single Peptide Aptamers Aubin-Tam, Marie-Eve; Appleyard, David C; Ferrari, Enrico ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
04/2011, Letnik:
115, Številka:
16
Journal Article
Recenzirano
Odprti dostop
Aptamer and antibody mediated adhesion is central to biological function and is valuable in the engineering of “lab on a chip” devices. Single molecule force spectroscopy using optical tweezers ...enables direct nonequilibrium measurement of these noncovalent interactions for three peptide aptamers selected for glass, polystyrene, and carbon nanotubes. A comprehensive examination of the strong attachment between antifluorescein 4−4−20 and fluorescein was also carried out using the same assay. Bond lifetime, barrier width, and free energy of activation are extracted from unbinding histogram data using three single molecule pulling models. The evaluated aptamers appear to adhere stronger than the fluorescein antibody under no- and low-load conditions, yet weaker than antibodies at loads above ∼25 pN. Comparison to force spectroscopy data of other biological linkages shows the diversity of load dependent binding and provides insight into linkages used in biological processes and those designed for engineered systems.
Pollen grains have the potential to be effective plant-based biorenewable fillers in polymer matrices due to their high modulus, strength, chemical stability, and unique nanoscale architectures. In ...this work, we present evidence for the effectiveness of pollen as a reinforcing filler in epoxy matrices, characterized as a function of pollen loading and surface treatment. Composites prepared with unmodified native defatted ragweed pollen (D) displayed decreased mechanical properties and increasing glass transition temperatures (
T
g
) with increasing pollen loading. A soft interphase was observed to form around native pollen that is likely due to incompletely cured epoxy, resulting in decreased mechanical properties. However, pollen treated via a common base-acid (BA) surface preparation was a load-bearing, toughening filler in epoxy composites, displaying simultaneously increased tensile strength (by 47%) and strain at break (by 70%), improving interfacial morphology (absence of soft interphase), and increasing
T
g
at 10 wt% pollen loading. Elastic modulus improves by 14% with 10 wt% BA pollen loading, and fitting of the modulus with the Halpin-Tsai and Counto models results in an estimated pollen exine modulus of 8 GPa, the first reported pollen modulus measurement from composite studies. Improvements in mechanical properties in BA pollen versus D pollen likely result due to crosslinks with the epoxy matrix due to the presence of protic functional groups (hydroxyls or carboxyls) on the BA surface. BA-treated ragweed pollen shows promise as a toughening filler for imparting higher strength to polymers without increasing mass.
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