Assemblies of Functional Peptides and Their Applications in Building Blocks for Biosensors

This feature article highlights our recent applications of functional peptide nanotubes, self‐assembled from short peptides with recognition elements, as building blocks to develop sensors. Peptide nanotubes with high aspect ratios are excellent building blocks for a directed assembly into device configurations, and their combined structures with nanometric diameters and micrometric lengths enables to bridge the “nanoworld” and the “microworld”. When the peptide‐nanotube‐based biosensors, which incorporate molecular recognition units, apply alternating current probes to detect impedance signals, the peptide nanotubes behave as excellent building blocks of the transducer for the detection of target analyes such as pathogens, cells, and heavey metal ions with high specificity. In some sensor configurations, the electric signal can be amplified by coupling them with ion‐specific mineralization via molecular recognition of peptides. In general the detection limit of peptide nanotube chips sensors is very low and the dynamic range of detection can be widened by improved device designs.     

Understanding the Mechanism of Solvent‐Mediated Adhesion of Vacuum Deposited Au and Pt Thin Films onto PMMA Substrates

The adhesion of vapor deposited Au and Pt thin films onto poly(methyl methacrylate) (PMMA) substrates can be significantly enhanced by either spin‐casting or vapor‐exposure to hydrohalocarbon solvents prior to metal deposition. X‐ray photoelectron spectroscopy (XPS) and evolved gas analysis Fourier transform infrared spectroscopy detect residual halogenated solvent at the PMMA surface which chemically activates the surface. Density functional theory (DFT) calculations show that the solvent molecules form a Lewis acid‐base adduct with the ester oxygens in PMMA. DFT predicts that the deposited metal atom (M) inserts into the C–halogen (X) bond on either CHCl₃ or CHBr₃ to form a O–M–X interaction. This is consistent with M–X bonding observed in high resolution XPS. A model is proposed in which the bond energy of the C–X bond of the solvent must be weak enough so that it can be cleaved by the metal atom to form a M–X bond. A negative control of PMMA exposed to CHF₃ is shown to have no effect on Au or Pt adhesion since the bond dissociation energy of the C–F bond is stronger than the C–Cl and C–Br bond energy compared to the metal halide bond energies.     

Ambient‐Dried, 3D‐Printable and Electrically Conducting Cellulose Nanofiber Aerogels by Inclusion of Functional Polymers

This study presents a novel, green, and efficient way of preparing crosslinked aerogels from cellulose nanofibers (CNFs) and alginate using non‐covalent chemistry. This new process can ultimately facilitate the fast, continuous, and large‐scale production of porous, light‐weight materials as it does not require freeze‐drying, supercritical CO₂ drying, or any environmentally harmful crosslinking chemistries. The reported preparation procedure relies solely on the successive freezing, solvent‐exchange, and ambient drying of composite CNF‐alginate gels. The presented findings suggest that a highly‐porous structure can be preserved throughout the process by simply controlling the ionic strength of the gel. Aerogels with tunable densities (23–38 kg m^?3) and compressive moduli (97–275 kPa) can be prepared by using different CNF concentrations. These low‐density networks have a unique combination of formability (using molding or 3D‐printing) and wet‐stability (when ion exchanged to calcium ions). To demonstrate their use in advanced wet applications, the printed aerogels are functionalized with very high loadings of conducting poly(3,4‐ethylenedioxythiophene):tosylate (PEDOT:TOS) polymer by using a novel in situ polymerization approach. In‐depth material characterization reveals that these aerogels have the potential to be used in not only energy storage applications (specific capacitance of 78 F g^?1), but also as mechanical‐strain and humidity sensors.