We report exceptional optical limiting properties of two kinds of Ag nanoprisms (pure Ag nanoprisms and Au@Ag core-shell nanoprisms) in solution that were photochemically prepared. Fluence-dependent transmittance measurements using 7ns laser pulses of 532nm wavelength showed that the optical limiting properties of two kinds of silver nanoprisms in solution are slightly better than that of carbon nanotube suspensions, which is known as a benchmark optical limiter. Nonlinear scattering experiments suggested that nonlinear scattering should play an important role in the observed optical limiting effects.
Photocurrent generation and photodetection are usually based on semiconductor crystals including Si, CdS, and PbS. This work reports the enhanced photoabsorption and photodetection of close-packed metallic Au nanoparticles ͑NPs͒ in the UV-VIS ͑visible͒-NIR ͑near infrared͒ region. Photoabsorption in the UV-VIS regions is associated with the interband transition and surface plasmon resonance of AuNPs, while the enhanced NIR absorption is due to the collective effect of interacting AuNPs in the close-packed network. Consequently, the AuNPs exhibits photodetection behavior in the wavelength range of 300-1500 nm. It is proposed that the inter-AuNP photoejection and delocalization of electron-hole pairs changes the carrier lifetime and transit dynamics in favor of photocarrier conduction, thus significantly facilitating photocurrent generation in the metallic AuNP close-pack. Moreover, due to the power-law conduction mechanism in AuNP networks, the quantum yield of AuNPs can be tuned from 10 −6 to 10 −1 photoelectron/photon by increasing the bias voltage from 0 to 5 V. The AuNP quantum yield of 10 −1 at 5 V is as high as that of commercial Si photodetectors at 0 V, and this demonstrates the immediate applicability of AuNPs in photodetection. In view of the compatibility of AuNPs with wet-chemistry and inkjet printing processes at low temperatures, metallic AuNPs may provide a convenient alternative to semiconductor crystals in photodetection and perhaps photovoltaic applications.
Unique character and common behavior are two distinguished things. In frontier nanoscience and nanotechnology, unique characters were normally obtained in some novel exotics materials such as metal-metal core-shell materials, metallic-semiconducting hybrid nanomaterials, and organic-inorganics complex nano-compounds. On the other hand, normal behavior of natural phenomena including in nano-size objects were obviously predicted based on their exact size related to confinement effect, and capability to interact with another physical system in nature. Here, we report an example of unique character due to evolution nonlinear behavior observed in gold nanorod with their aspect-ratio dependence of optical nonlinearities investigated by femtosecond Z-scan measurements closed to resonance longitudinal surface plasmon peak in gold nanorods (Au NRs). Saturable absorption manifests itself at low excitation (laser irradiances < ~7.0 GW/cm2), while reverse saturable absorption dominates at higher excitation. Both the nonlinear processes are found to increase with the aspect ratio of Au NRs. Based on the discrete dipole approximation, qualitative explanations are presented for the observed nonlinear behavior. While common behavior in metallic quantum dots or other shapes of metallic nanomaterials was not the significant in our observation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.