This paper reports a convenient approach for one-pot, facile, photochemically assisted synthesis of stable silver colloids (Ag) by using dithizone (DTZ)/its oxidation products (DTZH) as a reductant/particle stabilizer without any extra control such as surfactant or pH. Although dithizone chemistry has been studied extensively, it is surprising to note that there are hardly any studies published thus far on photochemically assisted formation of metallic nanomaterials using dithizone. We revisit the chemistry of dithizone based upon previous reports and synthesize silver nanoparticles (Ag–DTZH) photochemically using dithizone. The prepared hybrid nanomaterial (Ag–DTZH) has been characterized by UV-visible spectroscopy, infrared spectroscopy, cyclic voltammetry, transmission electron microscopy, field-emission scanning electron microscopy and X-ray photoelectron spectroscopy techniques. Nanosilver formation by exposure to light is studied for various time intervals using UV-visible spectroscopy as well as TEM. This hybrid material derived from nanoscale silver protected with dithizone and its oxidation product has been further utilized for electro-sensing of cefotaxime (CFX), which is a third-generation cephalosporin antibiotic drug. Moreover, a possible reaction mechanism for the formation of silver nanostructures has been proposed. Modified electrodes with hybrid nanomaterial (Ag–DTZH) efficiently electro-catalyzes the oxidation of cefotaxime at the potential of 0.789 V vs. AgCl/Ag and shows a linear response toward cefotaxime sensing with 0.244 μA μM⁻¹ sensitivity and a 15.32 nM limit of detection at signal-to-noise ratio (S/N): 3. The electrochemistry behind this sensing of cefotaxime is probably due to high connectivity throughout the silver nanostructure (Ag–DTZH) capped with dithizone and its oxidation product over the modified electrode. It exhibits high-electron transfer kinetics via the interaction of Ag–DTZH with –NH₂ and –COOH groups present in CFX. The present finding will open new avenues in the field of electro-sensing of analytes with this hybrid material-modified electrode.