Scalable Routes to Gold Nanoshells with Tunable Sizes and Response to Near‐Infrared Pulsed‐Laser Irradiation

Abstract

We present a simplified synthesis of hollow gold nanoshells 20-50 nm in diameter via the wellestablished templated galvanic replacement reaction of silver for gold. The surface plasmon resonance absorbance of nanoshells made in this fashion can be tuned using basic colloid chemistry to control the size of the silver templates. The gold nanoshells can be varied in size and shell thickness depending on silver/gold reagent ratios and have an aqueous core. The template replacement chemistry is rapid, highly scalable, uses minimal amounts of toxic reagents, and in many cases is a true `one pot' synthesis. The smallest nanoshells (20 nm diameter, 7 nm wall thickness) reach the highest temperature on irradiation with femtosecond light pulses in the near infrared and anneal to form spherical nanoparticles fastest, even though their plasmon resonance does not overlap as well as the larger nanoshells (50 nm diameter, 7 nm wall thickness) with the 800 nm wavelength excitation. Optimizing a nanoshell structure to reach the highest nanoshell temperature is not the same as optimizing the structure for maximum energy absorbance.

Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing

“…Prevo et al investigated the effect of a femtosecond laser on hollow gold spheres of different sizes [170]. Previous work studying the effect of pulsed laser on nanoparticles showed that exposure to irradiation resulted in fragmentation of particles and the generation of new extinction peaks associated with the new population [161,169,[171][172][173].…”

“…Previous work studying the effect of pulsed laser on nanoparticles showed that exposure to irradiation resulted in fragmentation of particles and the generation of new extinction peaks associated with the new population [161,169,[171][172][173]. In this work, particles with diameters ranging from 20 to 50 nm with SPRs ranging from 550 to 750 nm were subjected to NIR pulsed light for 10 min at two different powers (350 and 700 J) [170]. For the higher power, regardless of size, all nanoparticles sintered and annealed in to solid spheres, producing a shift in their initial extinction peak to one that fell between 500-550 nm [170].…”

“…In this work, particles with diameters ranging from 20 to 50 nm with SPRs ranging from 550 to 750 nm were subjected to NIR pulsed light for 10 min at two different powers (350 and 700 J) [170]. For the higher power, regardless of size, all nanoparticles sintered and annealed in to solid spheres, producing a shift in their initial extinction peak to one that fell between 500-550 nm [170]. For the lower power, the hollow spheres broke in to asymmetric incomplete shells, oblate spheroids, rods and branched structures.…”

“…For the lower power, the hollow spheres broke in to asymmetric incomplete shells, oblate spheroids, rods and branched structures. These spheres also saw the loss of their initial absorption peak and the creation of a new peak at bluer wavelengths [170]. This determination of power dependence with respect to fragmentation is important when considering an application like drug delivery where it is necessary to induce the release of material from the inner cavity of the HGN through collapse of the external structure [174,175].…”

Synthesis of gold-poly (dimethylsiloxane) nanocomposite through a polymer-mediated silver/gold galvanic replacement reaction

“…Particularly, for Au and Ag, the resonance frequency of surface plasmon (SPR) can be tuned by adjusting the size and morphology or by alloying. In some cases, the SPR band could be shifted to the nearinfrared region, a region of particular interest for biomedical applications such as for example, cancer hyperthermia [5,6].…”