Silicon nanoparticles (SiNPs) are promising materials for applications in enhanced oil recovery (EOR), sensing, anti-corrosion coatings, and catalysis due to their high surface area, tunable surface chemistry, and chemical stability. This protocol describes a minimal-step hydrothermal synthesis route for preparing silicon nanoparticles using a silicon precursor under controlled temperature and pressure conditions. The hydrothermal method offers a relatively low-cost, scalable, and contamination-controlled approach compared to high-temperature gas-phase techniques. The synthesized SiNPs can be tailored in the 20–150 nm range by adjusting precursor concentration and reaction time. The resulting particles are suitable for dispersion in aqueous or organic systems for oil & gas sector applications.
This protocol describes the hydrothermal synthesis of silicon nanoparticles using sodium silicate solution as the silicon source under controlled alkaline conditions. The process begins with dilution of sodium silicate in deionized water followed by controlled pH adjustment to initiate hydrolysis and condensation reactions that form nanoscale silicate nuclei. The reaction mixture is transferred into a Teflon-lined stainless-steel autoclave and subjected to hydrothermal treatment at elevated temperature and autogenous pressure. Under these conditions, nucleation and growth of silicon-based nanoparticles proceed uniformly, resulting in well-dispersed nanoscale particles with narrow size distribution. After completion of the reaction, the system is allowed to cool naturally to room temperature to prevent sudden aggregation. The product is separated, washed repeatedly to remove residual ions, and dried at moderate temperature to obtain free-flowing silicon nanoparticles.
The hydrothermal environment enhances particle uniformity, reduces uncontrolled agglomeration, and improves structural stability compared to conventional precipitation methods. The synthesized nanoparticles are suitable for dispersion in aqueous nanofluids for reservoir wettability modification, permeability enhancement, corrosion-resistant coatings, and scale inhibition systems. This method is scalable, cost-effective, and compatible with industrial material preparation requirements in oil and gas sector applications.
Sterlization Module module step
Label a clean beaker as “SiNP Batch – Hydrothermal”.Add 40 mL DI water to the beaker.Add 10 mL sodium silicate solution slowly under stirring.Stir for 10 minutes at room temperature until fully homogeneous.
Measure initial pH.Prepare 1 M NaOH solution (fresh).Add NaOH dropwise with stirring until pH = 10.5 ± 0.5.Continue stirring for 15 minutes.
Ensure Teflon liner and gasket are clean and dry.Transfer mixture into the liner.Fill limit: Do not exceed 80% liner volume.Seal the autoclave tightly as per manufacturer instructions.
Place sealed autoclave in oven/reactor.Heat to 180°C.Hold at 180°C for 8 hours.After completion, turn OFF heat and allow natural cooling to room temperature (typically several hours).Open autoclave only after fully cooled.Pour reaction mixture into centrifuge tubes.Centrifuge at 6000–9000 rpm for 10 minutes.Decant supernatant carefully without disturbing pellet.
Add DI water to the pellet, vortex/shake to resuspend.Centrifuge again (6000–9000 rpm, 10 minutes). Decant.Repeat DI water wash 3×.Perform Ethanol wash 1× (optional but recommended for faster drying and lower agglomeration).Transfer washed pellet to a clean glass dish.Dry at 70°C for 6–10 hours.Lightly grind dried material using mortar-pestle to deagglomerate.
The hydrothermal synthesis method provides a controlled and effective approach for preparing silicon-based nanoparticles from sodium silicate solution. In this process, sodium silicate acts as an inexpensive and easily available precursor, while deionized water provides the reaction medium. Dilution of the precursor followed by controlled pH adjustment helps regulate hydrolysis and condensation reactions, which directly influence particle nucleation, growth, and aggregation.
The reaction mixture is transferred into a Teflon-lined stainless-steel autoclave and exposed to elevated temperature under autogenous pressure. These hydrothermal conditions promote more uniform particle formation compared with conventional precipitation methods. The controlled temperature and pressure environment can help improve particle size distribution and structural stability. The Teflon lining also reduces direct interaction between the reaction mixture and the metal surface of the autoclave, which helps minimize contamination.
After completion of the reaction, natural cooling is important because sudden temperature changes may promote aggregation and also create safety concerns due to the pressure inside the autoclave. The recovered nanoparticles are washed repeatedly to remove residual sodium ions, excess alkali, and unreacted precursor. Proper washing is essential because remaining ions can affect surface charge, dispersion stability, and downstream performance. Moderate-temperature drying helps obtain a free-flowing nanoparticle powder while limiting excessive agglomeration.
For oil and gas applications, well-dispersed nanoparticles may be useful in nanofluids for wettability modification, permeability studies, corrosion-resistant coatings, and scale-control systems. Their high surface area makes surface interactions particularly important. However, these applications should be supported by proper characterization. DLS and zeta potential can evaluate dispersion behaviour, TEM or SEM can examine morphology, XRD can study structure, and FTIR can confirm surface functional groups.
Overall, the hydrothermal method offers a simple, scalable, and reproducible route for preparing silicon-based nanomaterials for further industrial and research applications.
The hydrothermal method provides a simple and controlled approach for preparing silicon-based nanoparticles from sodium silicate solution. Careful control of precursor dilution, pH, temperature, reaction time, and cooling conditions helps improve particle formation and reduces uncontrolled aggregation. The use of a Teflon-lined autoclave creates a stable hydrothermal environment that supports uniform nucleation and growth of nanoscale particles. Proper washing and moderate-temperature drying are also important for removing residual ions and obtaining a stable final product.
The prepared nanoparticles can be further explored for oil and gas applications such as wettability modification, nanofluid formulation, corrosion-resistant coatings, permeability studies, and scale-control systems. However, their actual performance should be confirmed through suitable characterization techniques such as DLS, zeta potential, SEM or TEM, FTIR, and XRD. Overall, the method offers a reproducible and potentially scalable route for preparing silicon-based nanomaterials for further research and industrial evaluation.