Facile Solvothermal Preparation of Monodisperse Gold Nanoparticles and Their Engineered Assembly of Ferritin–Gold Nanoclusters

Herein, we report a quick and simple synthesis of water-soluble gold nanoparticles using a HAuCl₄ and oleylamine mixture. Oleylamine serves as a reduction agent as well as a stabilizer for nanoparticle surfaces. The particle sizes can be adjusted by modulating reaction temperature and time. Solvothermal reduction of HAuCl₄ with oleylamine can be confirmed by measuring the product in Fourier transform infrared (FTIR) spectroscopy. The plasmon band shifting from yellow to red confirms a nanosized particle formation. Amide bonds on the surface of the nanoparticles formed hydrogen bonds with one another, resulting in a hydrophobic monolayer. Particles dispersed well in nonpolar organic solvents, such as in hexane or toluene, by brief sonication. Next, we demonstrated the transfer of gold nanoparticles into water by lipid capsulation using 1-myristoyl-2-hydroxy-<i>sn</i>-glycero-3-phosphocholine (MHPC), 1,2-distearoyl-<i>sn</i>-glycero-3-phosphoethanolamine-<i>N</i>-(methoxy polyethylene glycol)-2000 (DPPE-PEG2k), and 1,2-dioleoyl-<i>sn</i>-glycero-3-<i>N</i>-{5-amino-1-carboxypentyl}­iminodiacetic acid succinyl nickel salt [DGS-NTA­(Ni)]. The particle concentration can be obtained using an absorbance in ultraviolet–visible (UV–vis) spectra (at 420 nm). Instrumental analyses using transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis, dynamic light scattering (DLS), and FTIR confirmed successful production of gold nanoparticles and fair solubility in water. Prepared gold particles were selectively clustered via engineered ferritin nanocages that provide multiple conjugation moieties. A total of 5–6 gold nanoparticles were clustered on a single ferritin nanocage confirmed in TEM. Reported solvothermal synthesis and preparation of gold nanoclusters may serve as an efficient, alternate way of preparing water-soluble gold nanoparticles, which can be used in a wide variety of biomedical applications

Simultaneous Removal of Divalent Heavy Metals from Aqueous Solutions Using Raw and Mechanochemically Treated Interstratified Montmorillonite/Kaolinite Clay

The removal of Pb­(II), Cd­(II), Cu­(II), and Zn­(II) from aqueous solutions using (un)­modified Serbian interstratified montmorillonite/kaolinite clay as an adsorbent was investigated. The clay was modified by mechanochemical activation for different time periods. X-ray diffraction patterns and particle size distributions were used to characterize the samples. Batch adsorption studies were conducted to optimize various conditions. The adsorption equilibrium was established within 60 min, and the maximum adsorption occurred in the pH range of 4.5–6.5. The milled clays exhibited greater equilibrium adsorption capacities (<i>q</i>_e) for all of the metals than the raw clay. A difference in <i>q</i>_e values for clays milled for 2 and 19 h could be observed only for initial concentrations (<i>C</i>_i) of ≥100 mg dm^–3. This was related to the amorphization (i.e., exfoliation) of 19-h-milled clay particles. The adsorption equilibrium data of heavy metals on both raw and modified clays fit the Langmuir equation, although there were changes in the microstructure of the clay. The mechanochemical treatment of the clay reduced the amount of adsorbent necessary to achieve a highly efficient removal of heavy metals by a factor of 5. Thus, the mechanochemically treated interstratified clay can be considered as an efficient adsorbent for the simultaneous removal of divalent heavy metals