Motion-sensitive position sensor using bacteriorhodopsin

Recent advances in the field of bionanotechnology: an insight into optoelectric bacteriorhodopsin, quantum dots, and noble metal nanoclusters

Molecular sensors and molecular electronics are a major component of a recent research area known as bionanotechnology, which merges biology with nanotechnology. This new class of biosensors and bioelectronics has been a subject of intense research over the past decade and has found application in a wide variety of fields. The unique characteristics of these biomolecular transduction systems has been utilized in applications ranging from solar cells and single-electron transistors (SETs) to fluorescent sensors capable of sensitive and selective detection of a wide variety of targets, both organic and inorganic. This review will discuss three major systems in the area of molecular sensors and electronics and their application in unique technological innovations. Firstly, the synthesis of optoelectric bacteriorhodopsin (bR) and its application in the field of molecular sensors and electronics will be discussed. Next, this article will discuss recent advances in the synthesis and application of semiconductor quantum dots (QDs). Finally, this article will conclude with a review of the new and exciting field of noble metal nanoclusters and their application in the creation of a new class of fluorescent sensors.

Mechanisms of pulse response and differential response of bacteriorhodopsin and their relations

Bacteriorhodopsin (BR) films are oriented and deposited on indium tin oxide conductive glass by using electrophoretic sedimentation and Langmuir-Blodgett methods to construct sandwich-type photocells, respectively. The pulse response photoelectric signal of the BR photocell under pulsed laser and the differential response photoelectric signal under irradiation of interval light are measured. The origins of these two types of photoelectric responses and their correlations are analyzed. The pulse response signal initiates from the ultrafast charge separation of the retinal and the proton translocation followed by the deprotonation and reprotonation of the Schiff base and its surrounding amino acids. This is a quick response and is the preceding reaction of the differential response. The differential response signal is caused by the charging and discharging of the continuous proton current of the BR light-driven proton pump at light-on and light-off, which is a slow process. The differential response is related to not only the construction of the BR photocell but also the coupling mode of measurement. To observe the differential response signal, the BR photocell must have large enough B3 and B3' components in its pulse response as well as an alternative coupling mode to measure it.