Green-synthesized nanoparticles for forensic science: synthesis control, analytical validation, applications, and translation challenges

Abstract Background Nanoparticles are increasingly investigated in forensic science for latent fingermark development, surface-enhanced Raman spectroscopy (SERS), trace drug and explosive detection, gunshot-residue analysis, surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS), and biological-evidence processing. However, conventional nanoparticle synthesis may involve hazardous reducing agents, organic solvents, energy-intensive conditions, and surface contaminants that can affect environmental sustainability and analytical compatibility. Green synthesis uses plant extracts, microorganisms, algae, or purified biomolecules as reducing and stabilizing systems, offering a potentially safer and more sustainable alternative. Main body This review critically examines plant-, microbial-, algal-, and biomolecule-mediated synthesis of metal and metal-oxide nanoparticles, with particular attention to reaction mechanisms, process variables, extract standardization, batch-to-batch reproducibility, scalability, and storage stability. The complementary roles and limitations of ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, zeta-potential analysis, electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller surface-area analysis are evaluated. Forensic applications are assessed according to nanoparticle composition, substrate compatibility, analytical sensitivity, selectivity, detection limit, reproducibility, real-sample testing, and comparison with established methods. Particular emphasis is placed on latent fingermarks, SERS-based detection, SALDI-MS, gunshot residue, forensic toxicology, questioned documents, and biological evidence. The review also examines sustainability, biosafety, regulatory requirements, and the potential roles of artificial intelligence, machine learning, portable instrumentation, and smartphone-assisted detection. Conclusion Green-synthesized nanoparticles offer promising surface properties and analytical functions for forensic science, but most reported applications remain at the proof-of-concept stage. Variability in biological materials, incomplete mechanistic characterization, limited quantitative benchmarking, and insufficient validation using realistic casework samples currently restrict routine implementation. Progress toward operational use will require standardized synthesis and quality-control procedures, transparent performance reporting, interlaboratory studies, environmental and toxicological assessment, and validation consistent with accredited forensic laboratory requirements.