Introduction: Rice husk has portrayed great potential in becoming a sustainable biomass source in producing silica, cellulose and carbon materials, which garnered widespread interest among researchers. The objective of the current study is to determine the morphological and compositional changes in rice husk due to the synergistic effects of thermochemical treatment. Methods: Washed and dried rice husk was blended into a fine powder and then subjected to step-wise heat treatment and acid digestion to produce white ash. The intermittent products, as well as the original rice husk and the final ash product, were characterised using analytical instruments to document the morphological and chemical composition changes. Results: This report highlights the production of pure rice husk ash using a step-wise treatment using a combination of thermochemical treatment and carbonisation. The results showed that a partial breakdown of the lignocellulose components was achieved using directed thermal treatment at low temperature. The ionic impurities were leached out in subsequent heated acid treatment. Thereafter, the carbonaceous organic matter was completely converted to carbon during the carbonisation of the sample and the remaining carbon residue was removed during calcination. High purity ash contained agglomerated and nanostructured silica in the dimensions of 20 to 50 nm in the amorphous form. Conclusion: The step-wise treatment allowed systematic removal of each compound while maintaining the amorphous mineral phase of silica and avoiding carbon fixation. Understanding the effect of each treatment offers insight to produce purer silica from rice husk.

Introduction: Application of nano-engineered fingerprint dusting powders has been a recent trend to achieve latent fingermark development with superior ridge clarity. As such, efforts have been made to utilise natural resources to increase the sustainability of these emerging nano-engineered powders. Lithium-doped zinc oxide, primarily used as white pigments, have been previously applied to latent fingermarks with success. In the current study, nanostructured zinc oxide, synthesised using neem extract as the reducing agent, was evaluated for fingermark development on non-porous surfaces. Methods: The reduction of zinc nitrate hexahydrate was facilitated by neem extract, prepared by boiling neem leaves in distilled water. The thick yellow paste recovered was calcined in the furnace to produce a light yellow powder. Physicochemical composition of the powder was determined using microscopic and spectroscopic instruments. The effectiveness of the powder was tested on natural fingermark deposited on several non-porous surfaces. Results: Nanostructured zinc oxide with particle size ranging in between 1 to 3 µm consisting of highly aggregated spherical particle with less than 100 nm dimensions were synthesised. Developed fingermarks revealed excellent ridge details and contrast on dark coloured surfaces. Studying the fingermark closely under scanning electron microscope displayed selective distribution of particle on the ridges of the fingermark residue and very minimal deposition on the fingermark valleys. Conclusion: Nanostructured zinc oxide fabricated using green chemistry approach can be applied for the development of fingermark. Nevertheless, future works can be undertaken to enhance particle dispersity and to confer strong photoluminescence to the zinc oxide nanoparticles.

Introduction: The most common method to emerge latent fingermarks on non-porous surfaces is powdering by applying commercial fingerprint powders. However, the chemical composition of the powder is often toxic and poses health hazards to humans. This study was endeavoured to explore the effectiveness and potential use of natural resources for the enhancement of latent fingermarks. Methods: Eggshells and clamshells were prepared in fine powder form, and latent fingermarks were developed using each powder. Five non-porous substrates were selected for fingermarks deposition; glass, aluminium can, plastic book cover, painted wood, and compact disc. Results: Both natural powders have successfully developed high-quality finger marks with high clarity of ridge characteristics in comparison to commercial fingerprint powder (positive control) and untreated fingermark (negative control) on most of the tested surfaces tested. The sebaceous fingermarks have shown the best quality fingermarks when developed with both powders. In the ageing study, it was found that most non-porous substrates bearing latent fingermarks exposed to the destructive conditions can be successfully visualised in the early period of exposure. Conclusion: Eggshell and clamshell powders are as effective as commercial white powder but preferrable to be applied because of the low cost, abundant and non-hazardous.