Tailorable and Biocompatible Supramolecular-Based Hydrogels Featuring two Dynamic Covalent Chemistries.

Dynamic covalent chemistry (DCC) has proven to be a valuable tool in creating fascinating molecules, structures, and emergent properties in fully synthetic systems. Here we report a system that uses two dynamic covalent bonds in tandem, namely disulfides and hydrazones, for the formation of hydrogels containing biologically relevant ligands. The reversibility of disulfide bonds allows fiber formation upon oxidation of dithiol-peptide building block, while the reaction between NH-NH functionalized C-terminus and aldehyde cross-linkers results in a gel.

Caught in the Act: Mechanistic Insight into Supramolecular Polymerization-Driven Self-Replication from Real-Time Visualization.

Self-assembly features prominently in fields ranging from materials science to biophysical chemistry. Assembly pathways, often passing through transient intermediates, can control the outcome of assembly processes. Yet, the mechanisms of self-assembly remain largely obscure due to a lack of experimental tools for probing these pathways at the molecular level.

Determination of the thermal boundary conductance of gold nanoparticles in aqueous solution using a method based on nanobubble generation.

We present a method to determine the thermal boundary conductance of gold nanoparticles in aqueous solution. The novel approach consists of two steps: first, measuring photoacoustic signals originated by laser-induced nanobubbles at different energies and, second, fitting the experimental data with a nanobubble generation model developed in a previous work. We used this method on gold nanoparticles with diameters from 10 to 70 nm.

Reducing the capacitance of piezoelectric film sensors.

We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series.

Laser-induced bubble generation on a gold nanoparticle: A nonsymmetrical description.

The modeling of bubbles initiated by laser-irradiated nanoparticles is of interest for many applications. There is at present no comprehensive physical picture for all the stages of the process. We present an alternative approach with a key assumption: the vapor bubble evolves adjacent to the nanoparticle.

Determination of nongeometric effects: equivalence between Artmann's and Tamir's generalized methods.

This work shows that all first- and second-order nongeometric effects on propagation, total or partial reflection, and transmission can be understood and evaluated considering the superposition of two plane waves. It also shows that this description yields results that are qualitatively and quantitatively compatible with those obtained by Fourier analysis of beams with Gaussian intensity distribution in any type of interface. In order to show this equivalence, we start by describing the first- and second-order nongeometric effects, and we calculate them analytically by superposing two plane waves.

Photoacoustic beam profiling of pulsed lasers.

We introduce a beam profiler of pulsed lasers based on the photoacoustic technique. The method assumes that the initial pressure distribution inside the acoustic cell follows the laser intensity pattern if absorbed energy relaxes rapidly. This initial pressure condition can be described as a superposition of acoustic modes of different amplitudes and phases.

Novel optical method for background reduction in resonant photoacoustics.

We report a new way of reducing the background originated by window absorption in resonant photoacoustics. The technique employs a secondary light source that is absorbed by the window but not by the gas sample. This auxiliary source is modulated 180 degrees apart from the one used to probe the gas.

Simple synchronic detection at audio frequencies through a PC sound card.

We present a simple personal computer based, synchronic detection system that emulates a lock-in amplifier at audio frequencies. The inputs of the sound card are used to acquire two sets of samples: the one to be measured, previously preamplified, and the reference. From the last one, two "quasiorthogonal" signals are derived to perform dual-phase detection.