Tuning the Growth of Chiral Gold Nanoparticles Through Rational Design of a Chiral Molecular Inducer.

The bottom-up production of chiral gold nanomaterials holds great potential for the advancement of biosensing and nano-optics, among other applications. Reproducible preparations of colloidal nanomaterials with chiral morphology have been reported, using cosurfactants or chiral inducers such as thiolated amino acids. However, the underlying growth mechanisms for these nanomaterials remain insufficiently understood. We introduce herein a purposely devised chiral inducer, a cysteine modified with a hydrophobic chain, as a versatile chiral inducer. The amphiphilic and chiral features of this molecule provide control over the chiral morphology and the chiroptical signature of the obtained nanoparticles by simply varying the concentration of chiral inducer. These results are supported by circular dichroism and electromagnetic modeling as well as electron tomography to analyze structural evolution at the facet scale. Our observations suggest complex roles for the factors involved in chiral synthesis: the chemical nature of the chiral inducers and the influence of cosurfactants.

Preparation of Cellulose Nanocrystals: Controlling the Crystalline Type by One-Pot Acid Hydrolysis.

Cellulose nanocrystals (CNCs) have aroused increasing interest owing to their renewable origin and excellent properties derived from their size and morphology. Based on their chain orientation, CNCs can be prepared as two main allomorphs (I or II). However, achieving pure CNC allomorphs still requires enhanced control on the CNCs synthesis process and improved understanding of the involved reaction parameters. In this work, we study in detail a set of parameters for CNC synthesis using one-pot acid hydrolysis and evaluate their influence on the outcome with respect to yield, purity, and repeatability. We also demonstrate that a fast, nondestructive, and accurate methodology based on dynamic light scattering is an efficient alternative to the usual structural analysis of the synthesis outcome. Finally, we provide an improved protocol to reliably obtain each allomorph with mass yields of 25% for type I and 40% for type II. Emphasis is put on the reduction of the environmental impact and the overall preparation time.