The development and application of nanowires for electrochemical sensors and biosensors are reviewed in this article. Next generation sensor platforms will require significant improvements in sensitivity, specificity and parallelism in order to meet the future needs in variety of fields. Sensors made of nanowires exploit some fundamental nanoscopic effect in order to meet these requirements. Nanowires are new materials, which have the characteristic of low weight with extraordinary mechanical, electrical, thermal and multifunctional properties. The advantages such as size scale, aspect ratio and other properties of nanowires are especially apparent in the use of electrical sensors such as electrochemical sensors and in the use of field-effect transistors. The preparation methods of nanowires and their properties are discussed along with their advantages towards electrochemical sensors and biosensors. Some key results from each article are summarized, relating the concept and mechanism behind each sensor, with experimental conditions as well as their behavior at different conditions.

Spinach thylakoids were immobilized onto multiwalled carbon nanotubes using a molecular tethering chemistry. The resulting thylakoid–carbon nanotube composites showed high photo-electrochemical activity under illumination. Multiple membrane proteins have been observed to participate in direct electron transfer with the electrode, resulting in the generation of photocurrents, the first of its kind reported for natural photosynthetic systems. Upon inclusion of a mediator, the photo-activity was enhanced. The major contributor to the photocurrent was the light-induced water oxidation reaction at the photosystem II complex. The thylakoid–MWNT composite electrode yielded a maximum current density of 68 μA cm⁻² and a steady state current density of 38 μA cm⁻², which are two orders of magnitude larger than previously reported for similar systems. The high electrochemical activity of the thylakoid–MWNT composites has significant implications for both photosynthetic energy conversion and photofuel production applications. A fuel cell type photosynthetic electrochemical cell developed using a thylakoid–MWNT composite anode and laccase cathode produced a maximum power density of 5.3 μW cm⁻², comparable to that of enzymatic fuel cells. The carbon based nanostructured electrode has the potential to serve as an excellent immobilization support for photosynthetic electrochemistry based on the molecular tethering approach as demonstrated in this work.

Cyanobacteria possess unique and exciting features among photosynthetic microorganisms for energy conversion applications. This study focuses on production of direct electricity using a cyanobacterium called Nostoc sp. (NOS) as a photo-biocatalyst immobilized on carbon nanotubes on the anode of photo-bioelectrochemical cells. By illuminating with light (intensity 76 mW cm⁻²) the NOS immobilized on a carbon nanotube (CNT) modified electrode generated a photocurrent density of 30 mA m⁻² at 0.2 V (vs. Ag/AgCl). The contribution of different photosynthetic pigments in NOS to the light capture was analyzed and chlorophyll-a was found to be the major contributor to light capture followed by phycocyanin. Further investigation using a set of inhibitors revealed that the electrons were redirected predominantly from PSII to the CNT through the plastoquinone pool and quinol oxidase. A rudimentary design photosynthetic electrochemical cell has been constructed using NOS/CNT on the anode and laccase/CNT on the cathode as catalysts. The cell generated a maximum current density of 250 mA m⁻² and a peak power density of 35 mW m⁻² without any mediator. By the addition of 1,4-benzoquinone as a redox mediator, the electricity generation capability was significantly enhanced with a current density of 2300 mA m⁻² and a power density of 100 mW m⁻². The power densities achieved in this work are the highest among ‘non-engineered’ cyanobacteria based electrochemical systems reported to date.