We have investigated the complex conductivity of silver nanowire thin films using terahertz time-domain spectroscopy. Maxwell-Garnett effective medium theory, which accounts for the effective complex conductivity of silver nanowires, is presented in detail theoretically and experimentally. The conductivity of nanowires exhibits a characteristic non-Drude response in which the applied terahertz field is polarized in the longitudinal nanowire direction. The non-Drude responses of the silver nanowires are explained by the Gans approximation and the Drude-Smith model, and both agree well with the experimental data. Our results provide a basis for further explorations of charge carrier dynamics in nanowire-based transparent electrode applications.

A set of hybrids having gradual variation in distances between hexaphyrin and bodipy moieties, given by uses of phenylene, biphenylene, and triphenyelene bridges was prepared. Efficient PET processes from bodipy (donor) to [26]- or [28]hexaphyrin (acceptor) were successfully observed, where the PET speed was controlled by intramolecular distances between the donor and the acceptor. UV irradiation at 515 nm raised a band corresponding to the bodipy absorption. As the time delayed, the bodipy bands decreased and new absorption bands at 615 and 580 nm corresponding to respective absorption bands of [28]- and [26]-hybrids gradually appeared. Whereas the femtosecond transient absorption spectra of [28]/[26]-hybrids having terphenylene bridges completely showed energy transfers from bodipy to hexaphyrin, irradiation of the hybrids using 615 and 580 nm pulses did not induce opposite ways of the PET process. On the basis of enlarged center-to-center-distances of [26]-hybrids than those of [28]-hybrids, the set of [26]-hybrids resulted in slow decay/rise processes. PET parameters obtained with the experiments were fairly consistent with the PET parameters calculated.

We investigate the complex conductivity of silver nanowire thin films using terahertz time-domain spectroscopy. The measured conductivity shows a characteristic non-Drude response unlike bulk metals. The interesting behavior is explained by the Gans approximation and the Drude-Smith model.A wide range of applications using transparent thin-film electrodes emerge in areas such as liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), touch screens, and solar cells. Metallic nanowires, especially silver nanowires (Ag NWs), are considered to be good candidates for these applications, since Ag NWs exhibit outstanding electrical conductivity as well as high mechanical flexibility due to the mesh-like network structures mixed with various composites [1][2][3]. Therefore, it is important to explore the electromagnetic response of the NWbased transparent thin films. Terahertz time domain spectroscopy (THz-TDS) is an excellent spectroscopic tool for measuring conductivity without requiring electrical contact or damage to the samples [3].In this work, we study spectroscopic measurements on the terahertz (THz) complex conductivity of transparent metal composites containing various filling fractions of Ag NWs (1-15%) (Figs. 1a and b). Atomic-force microscopy (AFM) confirms that the average diameter of the Ag NW is 90 nm with a standard deviation of 10 nm, and the average length is 5 μm with a standard deviation of 2 μm. Figure 1c shows the time-domain THz signals where the phase shifts of E sam (t) are negligibly small with some amplitude decreases. The frequency-domain analysis shown in Fig. 1b depicts decreases in amplitude transmission with increasing Ag NW filling fractions. Fig. 1. a, Optical transmittance and b, optical microscope (the scale bar is 10 μm) and atomic force microscope (the scale bar is 5 μm) images of AgNW films with varying filling fraction. c, The measured THz time-domain signals and sample modulation scheme (inset) d, The obtained THz frequency-domain signals.