ATR FT-IR absorption enhancement of a thin film under the photon-tunneling condition

A simple, yet very powerful technique for the spectral acquisition of an extremely thin film with enhanced absorption was explored. An infrared absorption of an extremely thin film confined between media of high refractive indices was greater than that of its bulk when the spectrum was acquired under the attenuated total reflection (ATR) condition with parallel (p) polarized radiation. The absorption enhancement was not observed under perpendicular (s) polarized radiation. Theoretical investigations indicated that the absorption enhancement was proportional to the integration of the mean square evanescent field within the film. The field integration under p-polarized radiation increased, while that under s-polarized radiation decreased as the thickness of the confined film became thinner. The maximum enhancement was observed when the film was sufficiently thinner than the penetration depth. The phenomena were experimentally investigated, and the results agreed very well with theoretical predictions.

Political connections, founder-managers, and their impact on tunneling in China’s listed firms

We investigate the impact of manager political connection and founder status on tunneling in China's listed firms from 2004 to 2010. By classifying the political connections into three dimensions with two categories of controlling ownerships, we find that overall manager political connection is negatively related to tunneling in private firms but positively related to tunneling in SOEs. The CPC/CPPCC-type connection is likely to protect firms from tunneling, while the official-type connection facilitates tunneling from firms. The impact of these two types of political connection on tunneling is stronger at the central level than the local level. A chairman's political connection has significantly greater influence on tunneling than a CEO's connection. We also find that firms with founder-managers have a stronger resistance to tunneling than those with non-founder-managers, which is still observed in firms with politically connected founder-managers. Our results show that the incentives of various managers towards tunneling depend on their motivation for establishing relevant political connections.

Self-assembled core-satellite gold nanoparticle networks for ultrasensitive detection of chiral molecules by recognition tunneling current

Chirality sensing is a very challenging task. Here, we report a method for ultrasensitive detection of chiral molecule l/d-carnitine based on changes in the recognition tunneling current across self-assembled core-satellite gold nanoparticle (GNP) networks. The recognition tunneling technique has been demonstrated to work at the single molecule level where the binding between the reader molecules and the analytes in a nanojunction. This process was observed to generate a unique and sensitive change in tunneling current, which can be used to identify the analytes of interest. The molecular recognition mechanism between amino acid l-cysteine and l/d-carnitine has been studied with the aid of SERS. The different binding strength between homo- or heterochiral pairs can be effectively probed by the copper ion replacement fracture. The device resistance was measured before and after the sequential exposures to l/d-carnitine and copper ions. The normalized resistance change was found to be extremely sensitive to the chirality of carnitine molecule. The results suggested that a GNP networks device optimized for recognition tunneling was successfully built and that such a device can be used for ultrasensitive detection of chiral molecules.