Experimental and Theoretical Observation of Photothermal Chirality in Gold Nanoparticle Helicoids.

Single-particle spectroscopy is central to the characterization of plasmonic nanostructures and understanding of light-matter interactions in chiral nanosystems. Although chiral plasmonic nanostructures are generally characterized by their circular differential extinction and scattering, single-particle absorption studies can extend our understanding of light-matter interactions. Here, we introduce an experimental observation of photothermal chirality which originated from circular differential absorption of chiral plasmonic nanostructures.

Time-resolved temperature-jump measurements and steady-state thermal imaging of nanoscale heat transfer of gold nanostructures on AlGaN:Er thin films.

For a nanostructure sitting on top of an AlGaN:Er thin film, a new thermal imaging technique is presented where dual cameras collect bandpass filtered videos from the H and S bands of Er emission. We combine this thermal imaging technique with our newly developed time-resolved temperature measurement technique which relies on luminescence thermometry using Er emission. This technique collects time-resolved traces from the H and S bands of Er emission.

Time-resolved universal temperature measurements using NaYF:Er,Yb upconverting nanoparticles in an electrospray jet.

Hexagonal upconverting nanoparticles (UCNPs) of NaYF:Er,Yb (ca. 300 nm) have been widely used to measure the temperature at the nanoscale using luminescence ratio thermometry. However, several factors limit their applications.

Near-field thermal imaging of optically excited gold nanostructures: scaling principles for collective heating with heat dissipation into the surrounding medium.

In this paper, we introduce a new optical temperature and thermal imaging technique combining near-field microscopy and Er photoluminescence thermometry. The tip aperture of 120 nm limits the spatial resolution of near-field thermal imaging. We use the technique with two different approaches towards local temperature measurement and thermal imaging.

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs.

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water.

Effect of Ions and Ionic Strength on Surface Plasmon Absorption of Single Gold Nanowires.

The local temperature change from a single optically excited gold nanowire, lithographically prepared on Al0.94Ga0.06N embedded with Er(3+) ions, is measured in air, pure water, and various concentrations of aqueous solutions of ionic solutes of NaCl, Na2SO4, and MgSO4.

Comparison of vapor formation of water at the solid/water interface to colloidal solutions using optically excited gold nanostructures.

The phase transformation properties of liquid water to vapor is characterized by optical excitation of the lithographically fabricated single gold nanowrenches and contrasted to the phase transformation properties of gold nanoparticles located and optically excited in a bulk solution system [two and three dimensions]. The 532 nm continuous wave excitation of a single gold nanowrench results in superheating of the water to the spinodal decomposition temperature of 580 ± 20 K with bubble formation below the spinodal decomposition temperature being a rare event. Between the spinodal decomposition temperature and the boiling point liquid water is trapped into a metastable state because a barrier to vapor nucleation exists that must be overcome before the thermodynamically stable state is realized.

Ultrasensitive molecular detection using thermal conductance of a hydrophobic gold-water interface.

The thermal conductance from a hydrophobic gold aqueous interface is measured with increasing solute concentration. A small amount of aqueous solute molecules (1 solute molecule in 550 water molecules) dramatically increases the heat dissipation into the surrounding liquid. This result is consistent with a thermal conductance that is limited by an interface interaction where minority aqueous components significantly alter the surface properties and heat transport through the interface.

Superheating water by CW excitation of gold nanodots.

A temperature-dependent photoluminescent thin film of Al(0.94)Ga(0.06)N doped with Er(3+) is used to measure the temperature of lithographically prepared gold nanodots.

Absorption cross section and interfacial thermal conductance from an individual optically excited single-walled carbon nanotube.

The heat generation and dissipation of an individual optically excited metallic single-walled carbon nanotube is characterized using a thermal sensor thin film of Al(0.94)Ga(0.06)N embedded with Er(3+).

Local temperature determination of optically excited nanoparticles and nanodots.

A thin film of Al(0.94)Ga(0.06)N embedded with Er(3+) ions is used as an optical temperature sensor to image the temperature profile around optically excited gold nanostructures of 40 nm gold nanoparticles and lithographically prepared gold nanodots.

Experimental and theoretical studies of light-to-heat conversion and collective heating effects in metal nanoparticle solutions.

We perform a set of experiments on photoheating in a water droplet containing gold nanoparticles (NPs). Using photocalorimetric methods, we determine efficiency of light-to-heat conversion (eta) which turns out to be remarkably close to 1, (0.97 < eta < 1.

Thermooptical properties of gold nanoparticles embedded in ice: characterization of heat generation and melting.

We investigate the system of optically excited gold NPs in an ice matrix aiming to understand heat generation and melting processes at the nanoscale level. Along with the traditional fluorescence method, we introduce thermooptical spectroscopy based on phase transformation of a matrix. With this, we can not only measure optical response but also thermal response, that is, heat generation.