1IntroductionCarbon nanomaterials such as single-or multi-walled nanotubes and grapheneh ave been extensively used as electrode modifiers in the preparation of electrochemical sensors andb iosensors.E lectrode nanostructuration with these carbon materials allows preparing scaffolds with improved conductivity and selectivity and with enhanced ability for the immobilization of biomolecules. In addition, carbon nanomaterials can be used to designs uitable strategies for signala mplificationt hus leading to significant improvements in sensitivity.M ore recently,a part from the above mentioned carbon nanomaterials,o ther forms of carbon nanoforms have emergeda sn ovel nanostructuration tools suitable to be employed also in the preparation of novel electrochemical sensors and biosensor designs achieving improved analytical performance. Carbon nanohorns,d ouble-walled carbon nanotubes,f ullerene (C60), carbon nanoparticles,a nd graphene quantum dots are examples of thesen ovel nanomaterials whose particular characteristics make them appropriate for the constructiono fb ioelectrochemical devices.I nt his review article,t he use of these carbon nanomaterials in the particular field of electrochemical immunosensors preparation is reviewed.Thea bove mentioned, so called, uncommon carbon nanomaterials have been employed in the designo fe lectrochemical immunoassays in order to enhance their analytical performance both from the standpoint of attain am ore effective and simple immobilization of immunoreagents as to get betterd etection limits.A si tw ill be commentedb elow,t his analytical enhancementc an be achieved by taking advantage of somes pecific properties of these materialss uch as the ability of carbon nanohornst o provide numerous surface confined carboxylg roups for covalent binding, or the excellent capability of fullerene (C60) to accelerate electron transfer,a sw ell as its ability for combination with other materials to improve biocompatibility or water solubility.A lthough there are other carbon nanomaterials which have been scarcely explored for applications in electrochemical biosensing, only those of these nanomaterials that have demonstrated already their usefulness for the preparation of electrochemical immunosensors have been considered in this article.
2Carbon NanohornsSingle-walled carbon nanohorns,S WCNHs (or simply CNHs) are ar elatively new type of carbon allotrope.O ne single CNH consists of au nique horn-shaped graphene sheet with al ength of 40-50 nm and ad iameter ranging between 2a nd 5nm ( Figure 1a) [1].C NHs are prepared by vaporizing pure graphite rods via CO 2 laser ablation without usinga ny metalc atalysts.T hus,a ni mportant advantage of this materials over i.e.c arbon nanotubes is that CNHs are essentially metal-free [2, 3] and can be used directly without post-treatment. Typically,C NHs assembles to form nanostructures similar to dahlia flowers composed of several units (Figure 1b) with ad iameter near from 100 nm [4,5].T he special properties of CNHs derive from the high conductivity...