There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Switches, and Actuators Masahiro Irie,*,† Tuyoshi Fukaminato,‡ Kenji Matsuda, and Seiya Kobatake †Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan ‡Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging. Also, plasmon-enhanced phenomena are highly interesting for multiple purposes, including, for instance, Raman spectroscopy of nearby analytes, catalysis, or sunlight energy conversion. In addition, plasmon excitation is involved in a series of advanced physical processes such as non-linear optics, optical trapping, magneto-plasmonics, and optical activity. Here, we provide the general overview of the field and the background for appropriate modelling of the physical phenomena. Then, we report on the current state of the art and most recent applications of plasmon resonance in Au NPs.

Surface plasmon resonance in gold nanoparticles: a review.

This critical review will present the role of nanoparticles (NPs) in the directions that are vital to the new field of nanomedicine, including imaging and drug delivery. We reflect on the physical properties that make NPs advantageous for in vivo efficacy, and review recent advances in major NP based biomedical applications. Critical questions of transport, uptake, and clearance will be discussed and illustrated through the success and opportunities of NP imaging and therapy on a photodynamic therapy (PDT) based NP system that has been developed in our lab over the past decade (540 references).

The unique role of nanoparticles in nanomedicine: imaging, drug delivery and therapy

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

This review describes the fundamental aspects of laser–gold nanoparticle (Au NP) interaction that leads to nanoscale energy deposition to the surroundings through light amplification and heat generation. Besides the importance of the primary process in physics and chemistry, application of the light–NP interaction has attracted significant interest from various areas ranging from analytical chemistry to material chemistry and biomedicine. Here we consider both mechanistic and application aspects. Our attention is focused on pulsed-laser-induced fast processes that revealed the heating–cooling dynamics of electrons, lattice (particle), and particle's environment. On the application side, we focus on material fabrication and processing that beat diffraction-limited resolution. Together, we will shed a light on the essence of research activities carried out in the past 10 years. In addition to an abundance of latest information obtained from currently available literature, this review includes figures obtained by our own calculations to provide readers with a better understanding of the basics of the optical properties and energy and heat-transfer processes of Au NPs, which are not familiar to photochemists.

https://ir.nctu.edu.tw:443/bitstream/11536/15830/1/000302045700002.pdf

Studies on the interaction of pulsed lasers with plasmonic gold nanoparticles toward light manipulation, heat management, and nanofabrication

The interaction between molecular exciton and localized surface plasmon (LSP) polarization has been investigated by measuring light scattering spectra of single gold nanoparticles coated with cyanine dye J-aggregate. The spectral dip reflecting absorption spectral band of the J-aggregate varies with the particle size and the distance between the J-aggregates and the surface of gold nanoparticles. By comparing the experimental results with theoretical calculations based on the Mie theory, we demonstrate that the LSP polarization affects the peak and shape of the J-aggregate absorption band when the exciton resonance peak locates near the LSP resonance peak and when the separation of the J-aggregate from the metal surafce is short. The modification of the J-aggregate exciton band induced by LSP is considered to be due to strong coupling between the molecular exciton transition and the LSP resonance of metallic nanoparticles.

Single Particle Spectroscopic Investigation on the Interaction between Exciton Transition of Cyanine Dye J-Aggregates and Localized Surface Plasmon Polarization of Gold Nanoparticles

Organic dye nanoparticles 1−13 nm in height and 10−45 nm in width were prepared by the reprecipitation method. With single-molecule/nanoparticle spectroscopy, two distinct types of nanoparticles were found:  particles with blue emission and particles with red emission. The difference in spectral characteristics is attributed to the presence of two morphological types of particles in the samples. The presence of two types of nanoparticles in the samples was further corroborated by our ability to separate blue nanoparticles from red nanoparticles by centrifugation.

Single molecule spectroscopy of organic dye nanoparticles.

An in situ spectroscopic study of the nanosecond laser-induced melting and size reduction of pseudospherical gold nanoparticles with 54 ± 7 nm diameter allowed the observation of a heating efficiency that was very dependent on the excitation wavelength. A remarkably greater efficiency was observed for the photothermal effect of interband excitation than that of intraband excitation. This noteworthy observation is ascribed to an altered electron heat capacity, ce, during photoexcitation depending on the excitation energy, which is a phenomenon that has not been realized previously. As a result, a 60% reduction of the specific heat capacity, cp, compared to that of bulk gold was obtained for interband excitation at 266 nm whereas the cp value for the excitation of the intraband transition at 532 nm was unaltered. A semiquantitative explanation was given for this striking phenomenon induced by interband excitation in which excitation−relaxation cycles of electrons upon excitation of 5d electrons to the 6sp b...

https://ir.nctu.edu.tw:443/bitstream/11536/5260/1/000278427600106.pdf

Remarkable Photothermal Effect of Interband Excitation on Nanosecond Laser-Induced Reshaping and Size Reduction of Pseudospherical Gold Nanoparticles in Aqueous Solution

Takayuki Uwada

Papers

Studies on the interaction of pulsed lasers with plasmonic gold nanoparticles toward light manipulation, heat management, and nanofabrication

Single Particle Spectroscopic Investigation on the Interaction between Exciton Transition of Cyanine Dye J-Aggregates and Localized Surface Plasmon Polarization of Gold Nanoparticles

Single molecule spectroscopy of organic dye nanoparticles.

Remarkable Photothermal Effect of Interband Excitation on Nanosecond Laser-Induced Reshaping and Size Reduction of Pseudospherical Gold Nanoparticles in Aqueous Solution

Multiscale Approach of Photochromism: Synthesis and Photochromic Properties of a Diarylethene in Solution, in Nanoparticles, and in Bulk Crystals