REVIEW 1700313 (1 of 11) © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.small-methods.com Chiro-Spintronics: Spin-Dependent Electrochemistry and Water Splitting Using Chiral Molecular Films Prakash Chandra Mondal, Wilbert Mtangi, and Claudio Fontanesi* DOI: 10.1002/smtd.201700313 to engage in the design and synthesis of suitable organic molecules, giving birth to a new research domain known as “organic spintronics.” [2] Organic molecules are fascinating, as they possess a number of convenient characteristics such as: (i) tun- able optoelectronic properties, (ii) versatile chemical functionalities, (iii) longer spin- diffusion length, (iv) they can be easily assembled on metal/semiconductor sur- faces, and (v) they have unique interfacial properties, which include the molecular quantum confinement effect. Overall, these distinctive factors pave the way to the production of organic, and/or hybrid, solid-state devices. [3] Interestingly, chiral molecules are capable of transporting preferential spin for long distances without losing spin coherence or with negligible spin diffu- sion. [4] In pioneering work in 1999, Ron Naaman and co-workers experimentally observed that the transmission of electrons passing through chiral molecular films is spin specific, that is, a specific chiral molecule allows only one type of electron spin to be transported through the molecule, and this effect has been termed as the “chiral-induced spin selectivity” (CISS) effect. [4] According to the CISS effect (Figure 1), charge transport through a chiral system depends on their spin, since the linear momentum of the electron is coupled to its spin, and thus elec- trons propagating from left to right have opposite spins to those moving from right to left. [5] Since chiral molecules have the potential to filter specific spin (“UP” or “DOWN,” depending on the chirality) from a mixture of spins (“UP” and “DOWN”), they can be employed to substitute one of the ferromagnetic electrodes in the GMR devices. The combination of the spin- filtering property of the chiral molecules and spintronics nur- tures a new-born research domain, called “chiro-spintronics” or chiral-based spintronics. Based on the CISS effect, electron spin current can be controlled at a molecular level, by utilizing chiral molecules as a spin-specific transport medium. The ability of chiral molecules to filter the spins makes them potentially good candidates for use in spin valves, where these molecules will be used as layers separating the conducting magnetic layers. Urdampilleta et al. demonstrated that a single- walled carbon nanotube decorated with magnetic molecules can, at a sufficient low temperature, act in just the same way as a conventional spin valve. [6] The use of chiral molecules would allow control over the spin-polarized current in the magnetic Molecular spintronics or spin-based electronics, which utilizes both the spin degrees of freedom and electron charge, has become a hot topic in modern science. Since the introduction of spintronics in 1988, many efforts have been devoted to controlling spin-polarized current using an external magnetic field, leading to the implementation of commercial solid-state devices based on the giant magnetoresistance effect. In molecular spintronics, much progress has been achieved with organic molecules, but the role played by chiral molecules is yet to be explored in detail, while it promises to play a role in the future. It has been proved that the interaction of electrons with chiral molecules is spin specific, as supported by several experimental tools, and by theoretical studies. This effect is named “chiral-induced spin selectivity” (CISS). CISS is based on the fact that chiral molecules exhibit spin-specific transport proper- ties, and hence can be used as a substitute for ferromagnetic materials. Here, recent spin-dependent electrochemistry results are highlighted, where chiral molecules are immobilized on a ferromagnetic electrode. Practical applica- tions of the CISS effect, for spin control of charge transport in complex molecular architectures, and in the water-splitting process are also reviewed. Chiro-Spintronics Dr. P. C. Mondal National Institute for Nanotechnology University of Alberta 11421 Saskatchewan Drive, Edmonton T6G 2M9, Canada Prof. W. Mtangi School of Natural Sciences and Mathematics Chinhoyi University of Technology Private Bag, 7724 Chinhoyi, Zimbabwe Prof. C. Fontanesi DIEF University of Modena and Reggio Emilia Via Vivarelli 10, Modena 41125, Italy E-mail: claudio.fontanesi@unimore.it The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.201700313. 1. Introduction The emergent field of “spintronics” [1] which aims to combine the control of the spin degree of freedom with electron charge transport, has the potential to lead to a tremendous growth in high-density information storage, faster information manipula- tion, less heat dissipation, low energy consumption, and cost- effective devices. Spintronics technology promises to be of high significance for use by mankind; and the drive toward the min- iaturization of semiconductor devices has fostered researchers Dedicated to Prof. Ron Naaman who discovered the CISS effect Small Methods 2018, 1700313