Diffusion of Gold Nanorods Functionalized with Thermoresponsive Polymer Brushes

Abstract

Understanding the diffusion of gold nanorods (AuNRs) and their composites in dispersion is important at fundamental level and in fields as diverse as material science, nanobiotechnology to drug delivery. The translational and rotational diffusion of AuNRs decorated with thermoresponsive poly( N-isopropylacrylamide) brushes having hydrophilic and hydrophobic end groups was investigated in the dilute regime by dynamic light scattering. The same series of functionalized AuNRs were studied in the isotropic concentrated dispersions by high-resolution NMR diffusometry. The dependence of translational and rotational diffusivity upon molecular weight and polymer end group were measured as a function of temperature in the region of the brush phase transition. The effective hydrodynamic radius of AuNR composites proved to be the most sensitive quantity to the temperature-induced phase transition of brushes, allowing the evaluation of the brush thickness in the swollen and collapsed states.

Gold nanospheres/nanorods as highly promising candidates for the hydrophilic/hydrophobic balance of poly(N-vinylcaprolactam): a thoughtful design of nanocomposites

“…The excitation wavelength was kept at 360 nm and the emission maximum was observed at a wavelength of ∼475 nm for ANS in PVCL aqueous solution which correlates well with the literature value. 33 The results in Fig. 2(a) show that the fluorescence intensity of ANS in PVCL aqueous solution has increased in the presence of the lowest concentration of AuNSs (0.002 nM).…”

Heterogeneity and Hysteresis in the Polymer Collapse of Single Core–Shell Stimuli-Responsive Plasmonic Nanohybrids

“…It is important to note that the DLS cumulant fit assumes isotropic scatterers and, in the case of the expanded nanohybrids, is likely a reasonable approximation of the size, especially when compared with the dimensions extracted from the SEM micrographs. However, in the case of the collapsed nanohybrids, the shell thickness is at least 82% smaller than the longest dimension of the core, resulting in anisotropic scatterers that require applying theoretical models to depolarized DLS to extract the precise dimensions. , Thus, our DLS measurements serve as an initial verification and qualitative approximation of the temperature-induced VPT rather than to determine the absolute sizes. The similar diameters measured at 50 °C for the two AuNR@pNIPAM samples may be the result of the much thinner, collapsed polymer shells, and, therefore, the AuNR core size dominated the overall hydrodynamic dimensions.…”

Nanostructuring the Interior of Stimuli-Responsive Microgels by N-Vinylimidazoles Quaternized with Hydrophobic Alkyl Chains

“…The temperature-induced volume-phase transition of microgels can be described using the phenomenological Boltzmann sigmoidal function (see eq ). − This approach will be applied in our investigation to each chemical functional group of the polymer network, detected by high-resolution NMR spectroscopy, i.e., where functional groups are specified by the superindices j . Quantity I j ( T ) refers to one or several spectral integrals of NMR resonances for functional groups j measured at temperature T , and I 0 j is the reference integral measured at temperatures below the transition temperature T t j , i.e., for microgels in the swollen state.…”