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Heat generation of plasmonic nanoparticles under photo-illumination is of great use as nanoscale sources for chemical reactions and materials processing; the term thermoplasmonics has been infiltrating in the research fields related to nanotechnology, which represents photothermal effects in plasmonics. In recent years, transition metal nitrides have attracted much attention as thermoplasmonic materials because of their excellent thermal properties compared with those of noble metals. The transition metal nitrides such as titanium nitride (TiN) and zirconium nitride (ZrN) exhibit optical properties similar to gold, and their melting points are very high; for instance, the melting points are 1337 and 3253 K for gold and ZrN, respectively. However, nanometer-sized materials are known to melt at lower temperatures compared with bulk melting points (e.g., around 580 K for gold nanoparticles); this phenomenon is called surface melting, premelting, surface diffusion, or photothermal reshaping. In the present work, we evaluated threshold temperatures of the laser-induced photothermal reshaping of ZrN nanocubes by the scattering micro-spectroscopy at the single-nanoparticle level. As a result, the threshold temperatures of the photothermal reshaping ranged from 1400 to 2100 K; these temperatures are much higher than that of the gold nanoparticles. This work proved that the transition metal nitrides are suitable for thermoplasmonics at higher temperatures compared to the noble metals.

Bottom-up processing of nanobiomaterials enables the creation of a variety of macroscopic structures in natural systems. Here, we use optical means to produce macroscopic-assembled structures of nanoparticles (NPs) from protein molecules by using light-induced bubble (LIB) generation under asymmetric pressure-driven flow in a microchannel. The broadband optical response of assembled NPs facilitates the application of photon pressure and photothermal convection when irradiated by using an infrared laser. The presence of a large amount of protein allows the generation of a vast number of stable LIBs from optically assembled metallic NP-fixed beads (MNFBs). In the case of more diluted albumin solutions, the shrinking of a single LIB can cause the aggregation of MNFBs via fg-level albumin (3.4 fg in the observation region), like a microscale bubblegum. The size of the resulting aggregate can be controlled by changing the concentration of protein. These findings can be used to devise production methods not only for broadband optical nanocomposites but also for label-free methods to detect an extremely small amount of protein.

Multiwavelength laser radar system was installed at Syowa Station in 1983 by the 24th Japanese Antarctic Research Expedition for measurement of the middle atmospheric phenomena in cooperation with International Middle Atmosphere Program (MAP). The laser radar can simultaneously shoot two kinds of laser pulses (0.6943μm : the fundamental wave, 0.3471μm : the second harmonic wave) by means of ruby laser with regulated repetition frequencies (maximum : 1Hz) and receive scattered light by a telescope with the 50 cmφ-lens in efficient diameter. The measurement can be done by using a photon counter for each wave and A-scope for the fundamental wave. The test observation had been successfully made in Japan and it showed the remarkable increases of the strato-spheric aerosol due to the volcanic eruption of Mt. El Chichon. It was also inferred that the size distribution of the particles in the aerozol layer is inhomogeneous.

A highly efficient natural light-harvesting antenna has a ring-like structure consisting of dye molecules whose absorption band changes through selective evolutionary processes driven by external stimuli, i.e., sunlight depending on its territory and thermal fluctuations. Inspired by this fact, here, we experimentally and theoretically demonstrate the selective assembling of ring-like arrangements of many silver nanorods with particular shapes and orientations onto a substrate by the light-induced force of doughnut beams with different colours (wavelengths) and polarizations in conjunction with thermal fluctuations at room temperature. Furthermore, the majority of nanorods are electromagnetically coupled to form a prominent red-shifted collective mode of localized surface plasmons resonant with the wavelength of the irradiated light, where a spectral broadening also appears for the efficient broadband optical response. The discovered principle is a promising route for "bio-inspired selective optical assembly" of various nanomaterials that can be used in the wide field of nanotechnology. [ABSTRACT FROM AUTHOR]

Single-molecule and ensemble time-resolved fluorescence measurements were applied for the investigation of the conformational dynamics of single-stranded DNA, ssDNA, connected with a fluorescein dye by a C6 linker, where the motions both of DNA and the C6 linker affect the geometry of the system. From the ensemble measurement of the fluorescence quenching via photoinduced electron transfer with a guanine base in the DNA sequence, three main conformations were found in aqueous solution: a conformation unaffected by the guanine base in the excited state lifetime of fluorescein, a conformation in which the fluorescence is dynamically quenched in the excited-state lifetime, and a conformation leading to rapid quenching via nonfluorescent complex. The analysis by using the parameters acquired from the ensemble measurements for interphoton time distribution histograms and FCS autocorrelations by the single-molecule measurement revealed that interconversion in these three conformations took place with two characteristic time constants of several hundreds of nanoseconds and tens of microseconds. The advantage of the combination use of the ensemble measurements with the single-molecule detections for rather complex dynamic motions is discussed by integrating the experimental results with those obtained by molecular dynamics simulation. [ABSTRACT FROM AUTHOR]

Fluorescence correlation spectroscopy (FCS) was applied to the quantitative evaluation of the local heating in small domains <1 m in solutions under the laser trapping condition in the presence of a near-infrared (NIR) laser beam at 1064 nm. On the basis of the translational diffusion coefficient of fluorescent molecules obtained by FCS, the relationship between temperature rise and the incident NIR laser power, T/P,were determined to be 62 ± 6, 49 ± 7, and 23 ± 1 deg K/W in ethylene glycol, ethanol, and water, respectively, while no remarkable temperature increase was observed for deuterated water. The value of T/P linearly increased as a function of / ( is the extinction coefficient of solvent at the wavelength and is the thermal conductivity of the medium).The validity and the applicability of the present method for the measurement of the local temperature increase were discussed by comparing the present results with previous ones by other various methods. [ABSTRACT FROM AUTHOR]

Femtosecond transient absorption microscopy was applied to the elucidation of ultrafast dynamics in a lead iodide perovskite solar cell. Space- and time-resolved detection revealed that rapid deactivation with a time constant of 0.7 ps took place without long-living species in submicron grains with the (CH3NH3)PbI3 capping layer, while the long-living component was detected in other areas. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (Au NPs) have applications to photothermal therapy because of their photothermogenic properties. The photoresponsiveness of Au NPs is largely affected by their size. The photothermogenic properties of different-sized Au NPs were investigated. The Au NPs with approximately 50nm diameter exhibited the most efficient photothermogenic activity, which was apparent from their in situ photocytotoxicity against HeLa cells. [ABSTRACT FROM AUTHOR]