Photoresponsive Selenium Nanoparticle Colloids: A Pathway toward Chalcogen-Based Liquid Semiconducting Materials

Abstract Conventional semiconductor technologies rely on pure, highly ordered crystalline solids in which electronic coherence and minimal defect densities enable band-like charge transport. Liquids, in contrast, generally lack long-range structural order and conduct electricity (if at all) through ionic motion or hopping mechanisms. The development of liquid materials exhibiting semiconducting behavior could therefore offer substantial advantages, including compositional versatility, tolerance to defects and impurities, environmental stability, and compatibility with scalable deposition techniques. In this work, we demonstrate that elemental selenium can be incorporated into systems based on the organic superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to form stable colloids of amorphous selenium nanoparticles at room temperature, as confirmed with a selection of characterization techniques. Electrochemical and optical experiments reveal reversible photoresponsive behavior and most likely mixed ionic-electronic transport. While illumination induces a pronounced decrease in impedance and an increase in current response, consistent with photogenerated charge carriers within the bulk selenium phase. Although the system remains structurally disordered and colloidal in nature, it poses several characteristics commonly associated with semiconducting materials. Consequently, these DBU-stabilized colloids present a promising, synthetically simple platform for liquid semiconducting media that could offer a pathway toward defect-tolerant soft materials. The results from this study form a foundation that can inspire an interest in a research area involving liquid semiconductors, soft electronics, adaptive materials, ionic-electronic coupling, and photodoped fluids.