Using a combination of Fourier transform infrared (FTIR) spectroscopy and solid-state nuclear magnetic resonance (SSNMR) techniques, the secondary structure of peptides anchored on gold nanoparticles of different sizes is investigated. The structure of the well-studied CALNN-capped nanoparticles is compared to the structure of nanoparticles capped with a new cysteine-terminated peptide, CFGAILSS. The design of that peptide is derived from the minimal amyloidogenic sequence FGAIL of the human islet polypeptide amylin. We demonstrate that CFGAILSS forms extended fibrils in solution. When constrained at a nanoparticle surface, CFGAILSS adopts a secondary structure markedly different from CALNN. Taking into account the surface selection rules, the FTIR spectra of CFGAILSS-capped gold nanoparticles indicate the formation of β-sheets which are more prominent for 25 nm diameter nanoparticles than for 5 nm nanoparticles. No intermolecular (13)C-(13)C dipolar coupling is detected with rotational resonance SSNMR for CALNN-capped nanoparticles, while CALNN is in a random coil configuration. Coupling is detected for CFGAILSS-capped gold nanoparticles, however, consistent with an intermolecular (13)C-(13)C distance of 5.0 ± 0.3 Å, in agreement with intermolecular hydrogen bonding in a parallel β-sheet structure.

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Ferroelectric/antiferroelectric thin/thick films with large positive or negative electrocaloric (EC) effects could be very useful in designing commercial refrigeration devices.

Lead-free 0.94NBT-0.06BT-xLa ceramics at x = 0.0-1.0 (%) were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. With increasing La 3+ content pyroelectric coefficient (p) and figures of merits greatly increase; however, the depolarization temperature (Td) decreases. p is 7.42 x 10-4 C.m-2 .°C-1 at RT at x=0.5% and 105.4 x10-4 C.m-2 °C-1 at Td at x=0.2%. Fi and Fv show improvements at RT from 1.12 (x=0%) to 2.65 (x10-10 m.v-1) (x=0.5%) and from 0.021 to 0.048 (m 2 .C-1) respectively. Fi and Fv show a huge increase to 37.6 x10-10 m.v-1 and 0.56 m2.C-1 respectively at Td at x=0.2%. FC shows values of 2.10, 2.89, and 2.98 (x10-9 C.cm-2. °C-1) at RT at 33, 100 and 1000 (Hz) respectively. Giant pyroelectric properties make NBT-0.06BT-xLa at x=0.2% and 0.5% promising materials for many pyroelectric applications.

Ferroelectric/antiferroelectric thin/thick films with large electrocaloric (EC) effect in a broad operational temperature range are very attractive in solid-state cooling devices. We demonstrated that a large positive electrocaloric (EC) effect (maximum ΔT~20.7 K) in a broad temperature range (~110 K) was realized in Pb0.97La0.02(Zr0.65Sn0.3Ti0.05)O3 (PLZST) relaxor antiferroelectric (AFE) thin film prepared using a sol-gel method. The large positive EC effect may be ascribed to the in-plane residual thermal tensile stress during the layer-by-layer annealing process, and the high-quality film structure owing to the utilization of the LaNiO3/Pt composite bottom electrode. The broad EC temperature range may be ascribed to the great dielectric relaxor dispersion around the dielectric peak because of the coexistence of nanoscale multiple FE and AFE phases. Moreover, a large pyroelectric energy density (6.10 Jcm-3) was harvested by using an Olsen cycle, which is much larger than those (usually less than 10-4 Jcm-3) obtained by using direct thermal-electrical, Stirling and Carnot cycles, etc. These breakthroughs enable the PLZST thin film an attractive multifunctional material for applications in modern solid-state cooling and energy harvesting.

Fluorescence unquenching measurements of protease-dependent release of fluorescent biomolecules from peptide-capped gold nanoparticles reveal the effect of the monolayer composition on enzyme kinetics.