SEM images of silica structures synthesized by hydrolysis of 1 mM TEOS using 10 mM equivalent of (a–b) ammonia, and (c–d) L-serine amino acid in ionic liquid [BMIM][BF₄].

<p>SEM images of silica structures synthesized by hydrolysis of 1 mM TEOS using 10 mM equivalent of (a–b) ammonia, and (c–d) L-serine amino acid in ionic liquid [BMIM][BF₄].</p

SEM images of silica structures synthesized using arginine in IL [BMIM][BF₄] involving TEOS to arginine molar ratios of (a and b) 1∶10, (c) 1∶1, and (d) 1∶0.2 respectively.

<p>The insets show the higher magnification images of the structures shown in the corresponding main figure.</p

SEM images of silica structures synthesized using lysine in IL [BMIM][BF₄] involving TEOS to lysine molar ratios of (a and b) 1∶10, (c) 1∶1, and (d) 1∶0.2 respectively.

<p>The insets show the higher magnification images of the structures shown in the corresponding main figure.</p

SEM images of found in nature that have some resemblance to silica structures synthesized by cationic amino acid in ionic liquid [BMIM][BF₄].

<p>(a) <i>Isthima nervosa</i>, (b) <i>Cyclotella meneghiniana</i>, and (c) <i>Trigonium arcticum</i>. Reproduced by permission from <i>Trends in Biotechnology</i> [Drum R and Gordon R (2003) Star Trek replicators and diatom nanotechnology. <i>Trends Biotechnol</i> 21: 325–328]</p

Selected area electron diffraction (SAED) patterns obtained from silica superstructures obtained in ionic liquid [BMIM][BF₄] by hydrolysis of 1 mM TEOS using 10 mM of cationic amino acids (a) L-lysine, (b) L-arginine, and (c) L-histidine respectively.

<p>The diffused ring patterns are either from the TEM grid coated with an amorphous carbon film, and/or from the amorphous silica superstructures.</p

SEM images of silica structures synthesized using histidine in IL [BMIM][BF₄] involving TEOS to histidine molar ratios of (a and b) 1∶10, (c) 1∶1, and (d) 1∶0.2 respectively.

<p>The insets show the higher magnification images of the structures shown in the corresponding main figure.</p

XPS spectra showing Si 2p (a–c) and O 1s (d–f) core levels arising from SiO2 structures synthesized using 10 mM of lysine (a, d); arginine (b, e); and histidine (c, f) respectively.

<p>XPS spectra showing Si 2p (a–c) and O 1s (d–f) core levels arising from SiO2 structures synthesized using 10 mM of lysine (a, d); arginine (b, e); and histidine (c, f) respectively.</p

Optical microscopy images of PC3 human prostate cancer cells (control) grown for 24 h (A) in the absence of nanoparticles, and in the presence of (B) Mag and (C) Mag@SiO2 nanoparticles followed by three washings with PBS.

<p>Optical microscopy images of PC3 human prostate cancer cells (control) grown for 24 h (A) in the absence of nanoparticles, and in the presence of (B) Mag and (C) Mag@SiO2 nanoparticles followed by three washings with PBS.</p

XRD patterns obtained from Mag and Mag@SiO2 nanoparticles.

<p>XRD peaks with corresponding Bragg reflections of magnetite have been indicated. (*) corresponds to the XRD peak arising from a mixed Fe-Si phase.</p

Evaluation of Mag@SiO2 nanoparticles as a T2 MR contrast agent is shown in the form of % signal enhancement with increasing concentration of Fe using a 3 Tesla MR scanner.

<p>Panel A shows the studies performed in phantoms for particles in suspension, while panel B shows the similar studies in PC3 human prostate cancer cells after nanoparticles uptake for 24 h. Corresponding T2-weighted MR images of different samples, showing the image darkening effect with increasing Fe concentration are also shown under each bar.</p