Surfactant-Directed Anisotropic Growth of Elemental Selenium into Multilayered Two-Dimensional Nanosheets

Abstract Selenium (Se) is an essential trace element that plays a key role in antioxidant defense and is an important material in optoelectronic and materials science applications. However, bulk selenium exhibits poor physical and chemical properties, limiting its practical usability. To address these limitations, elemental selenium in the form of selenium nanoparticles have emerged as a promising class of nanomaterials. Although selenium nanoparticles (SeNPs) are widely explored for applications such as drug delivery and biosensing, two-dimensional (2D) selenium nanosheets (SeNSs) offer significantly higher surface-to-volume ratios compared to their three-dimensional counterparts. Current strategies for synthesizing SeNSs require extreme temperatures, high-vacuum environments, and prolonged processing times. To address these limitations, we report a facile, room-temperature, bottom-up synthesis of two-dimensional selenium nanosheets (SeNSs) using l-cysteine as a mild reducing agent and cetyltrimethylammonium bromide (CTAB) as a shape-directing surfactant. High-resolution SEM, TEM, and AFM imaging confirmed the formation of multilayered 2D sheets (∼0.4 μm lateral dimension) through CTAB templating. Characterization via XRD, Raman, and XPS revealed nonoxidized, semi-crystalline SeNSs containing coexisting trigonal (t-Se) and monoclinic (m-Se) phases. Electrical testing demonstrated enhanced charge transport compared to spherical selenium nanoparticles, featuring diode-like I–V characteristics with a ∼1.5 V turn-on voltage and an ideality factor of n = 2.5 ± 0.9. The cationic SeNSs (+25.5 mV zeta potential) enabled instantaneous electrostatic adsorption of methyl orange dye. Furthermore, SeNSs exhibited intrinsic redox activity, driving the spontaneous reduction of gold precursor into monodisperse gold nanoparticles (∼30 nm) without external reagents. This ambient, one-pot aqueous route eliminates high-energy processing and provides a sustainable, scalable strategy for integrating functional 2D selenium into next-generation technologies.