A colorimetric immunosensor based on local surface plasmon resonance by gold nanoparticles is presented, and its application for the detection of human immunoglobulin G (IgG) is demonstrated. The color change of the colloidal solution is produced by nanoparticle aggregation, a process that can be tuned by the presence of the analyte once the nanoparticles are functionalized. In comparison to common functionalization techniques, the procedure described here is simpler, low-cost, and effective in binding antibodies upright on the gold surface. The dose–response curve is similar to that resulting in typical immunoassay platforms and is satisfactorily described by the proposed theoretical model. Human IgG at concentration levels of few hundreds of nanograms per milliliter can be detected by eyes within a few minutes, thereby making the colorimetric immunosensor proposed here a powerful tool in several areas, with urine test in medical diagnostics being the most immediate.

In the manifold of materials for Volatile Organic Compound (VOC) sensing, graphene related materials (GRMs) gain special attention thanks to their versatility and overall chemico-physical tunability as a function of specific applications. In this work, the sensing performances of graphene-like (GL) layers, a new material belonging to the GRM family, are tested against ethanol and n-butanol. Two typologies of GL samples were produced by employing two different approaches and tested in view of their application as VOC sensors. The experiments were performed under atmospheric pressure, in dry air, and at room temperature and demonstrated that the sensing capabilities are related to the film surface features. The results indicated that GL films are promising candidates for the detection of low concentrations of VOCs at room temperature. The present investigation thus paves the way for VOC sensing optimization using cost-effective and easily scalable materials.

Graphene oxide (GO) is a two-dimensional material with peculiar photoluminescence emission and good dispersion in water, that make it an useful platform for the development of label-free optical biosensors. In this study, a GO-porous silicon (PSi) hybrid device is realized using a covalent chemical approach in order to obtain a stable support for biosensing applications. Protein A, used as bioprobe for biosensing purposes, is covalently linked to the GO, using the functional groups on its surface, by carbodiimide chemistry. Protein A bioconjugation to GO-PSi hybrid device is investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle (WCA) measurements, Fourier transform infrared (FTIR) spectroscopy, steady-state photoluminescence (PL), and fluorescence confocal microscopy. PSi reflectance and GO photoluminescence changes can thus be simultaneously exploited for monitoring biomolecule interactions as in a multi-parametric hybrid biosensing device.