Published in Micro & Nano Letters Received on 23rd October 2009 Revised on 11th March 2010 doi: 10.1049/mnl.2010.0020 ISSN 1750-0443 Synthesis of Ca(OH) 2 nanoparticles by wet chemical method A. Roy J. Bhattacharya Department of Mining Engineering, Indian Institute of Technology, Kharagpur 721302, India E-mail: jayantaism@gmail.com Abstract: This Letter reports a process of preparation and characterisation of Ca(OH) 2 nanoparticles without using any surfactant. Ca(OH) 2 is frequently used as precipitant, catalyst, paint, toxic-waste remediation agent, adsorbent and so on. To prepare stable Ca(OH) 2 nanoparticles, a simple hydrolysis method was applied using Ca(NO 3 ) 2 . 4H 2 O as the precursor, aqueous NaOH as the precipitant and ethane-1,2-diol (ED) as the medium. The nanoparticles were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscope (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed that the nanoparticles are of about 47 nm in diameter and P3m1 hexagonal structure. The method is simple and effective so that nanoparticles are stable up to 45 days, confirmed by the XRD pattern. 1 Introduction The research on synthesis procedures of nanosized particles of Ca(OH) 2 presents revealing implications in both fundamental and applied science. However, literature on the preparation of moderately water soluble inorganic nanoparticles is rare [1], compared to studies concerning nanoparticles of water insoluble compounds (sulphides, oxides, metals and so on) [2–9]. Ca(OH) 2 nanoparticles are fit for use in rapid and high-volume water treatment, wall painting, carbonatic stone and wood conservation and so on [10–12]. Wilhemy and Matijevic [13] reported that the precipitation of metal hydroxides from corresponding salt solution is largely affected by temperature. Metal hydroxide precipitation is also affected by the concentration of reacting species and type of medium [14, 15]. Matijevic and Scheiner [16] and Sugimoto and Matijevic [17] reported that both reaction time and temperature affect the precipitation of metal hydroxides. Particularly above 1008C temperature, formations of nanoscale particles are rapid and sizes are found to be uniform [17]. Yura et al. [18] and Hamada and Metijevic [19] reported that the selection of an organic solvent can influence the size and shape of the particles obtained by precipitation reaction. The use of diols as solvents in the sol–gel method for preparation of metal hydroxides was also reported [13, 14]. Calcium hydroxide nanoparticles were synthesised by Salvadori and Dei [20] in diols using calcium chloride (CaCl 2 . 2H 2 O) as calcium precursor. In this Letter the authors used calcium nitrate (Ca(NO 3 ) 2 . 4H 2 O), as a precursor of calcium ions for the synthesis of calcium hydroxide nanoparticles. The present work emphasises the preparation and characterisation of Ca(OH) 2 nanocrystal by hydrolysing hydrated calcium nitrate in ethylene glycol (1,2-ethanediol) with the addition of aqueous sodium hydroxide at 1158C. Synthesised and agglomerated particles were peptised according to the procedure reported [21]. The particles obtained were characterised, for their chemical nature (Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis), the crystallinity (X-ray diffraction (XRD)) and the shape/size (high transmission electron microscopy (TEM)). 2 Experimental Calcium nitrate tetrahydrate (Ca(NO 3 ) 2 . 4H 2 O), ethane-1, 2-diol (ED) (guaranteed reagent, GR), sodium hydroxide and 2-propanol analytical grade were of Merck (Darmstadt, Germany). Water was purified by a Millipore Organex system (R ≥ 18 MV cm). In a typical run, 25 ml of ethylene glycol was heated in a conical flux at 1158C in an oil bath, and then 12 g of Ca(NO 3 ) 2 was introduced into Micro & Nano Letters, 2010, Vol. 5, Iss. 2, pp. 131–134 131 doi: 10.1049/mnl.2010.0020 & The Institution of Engineering and Technology 2010 www.ietdl.org