We synthesized magnetic nanoparticles (MNPs) by mixing aqueous solutions of
Nanoscale magnetic particles have attracted much attention because they are able to be transported to targeted locations [
Synthesis methods of magnetic nanoparticles (MNPs) have been developed for composing various kinds of MNPs and controlling the sizes in the range of 1–100 nm [
Nanometer-scale spheres show very interesting characteristic phenomena such as quantum size effect or magnetic quantum tunneling and have intrinsic instability over longer haul for the morphology. To stabilize MNP character, chemical coating on naked MNP surface was developed [
We have developed a method for synthesizing MNPs by mixing aqueous solutions of
In this research, we functionalized MNPs by the (3-aminopropyl)triethoxysilane (
We developed simple preparation method of MNP. The
In this time, we prepared three types of functionalized MNPs with (i) amino, (ii) phenyl or, (iii) carboxy groups (Figure
Schematic illustration of functionalization of magnetic nanoparticle by silanization procedure (a) and the capture and ionization of target pesticide by phenyl group-modified magnetic nanoparticle (b).
Fourier transform infrared (FT-IR) spectra were observed to confirm the modification of functional groups, respectively, even after washing the samples several times to remove physisorbed organic molecules. Zeta potential was also measured using a Zetasizer Nano ZS (Malvern, UK) for recognition. Before and after the modification, each sample was examined by CuK
In the capture and analysis experiments, pyriminobac methyl (Methyl 2-(4,6-dimethoxy-2-pyrimidinyloxy)-6-(1-methoxyiminoethyl) benzoate;
The usefulness of the MNPs for their trapping ability and as an ionization-assisting material in MS was confirmed by a matrix-assisted laser desorption/ionization (MALDI) time of flight (TOF) instrument (Voyager-DE-RP; Applied Biosystems, Germany) equipped with a nitrogen laser emitting at 337 nm. The analyte surface was irradiated with 100 laser shots in the positive ion detection mode. As a control, the same procedure was conducted using the original unfunctionalized MNPs.
The XRD pattern of the iron-based MNP indicated the spinel
The CuK
FT-IR analysis exhibited the presence of Si–O (1100–900 cm−1) and O–H (3400–3100 cm−1) bonding as chemical bonds on the surface of the MNPs (Figure
The results of magnetization indicated different property by annealing temperature. In the case of the annealing temperature at 873 K, the magnetization of the iron-based MNPs increased linearly with increasing magnetic field; that is, the particle showed paramagnetism at 300 K (Figure
TEM images of the MNPs were shown (Figures
The modification of basic functional group such as amino, phenyl and carboxy groups is important because these groups can be used to bind various reagents by covalent bond or chemical interaction. FT-IR spectra indicated the existence of these functional groups on MNP, respectively. For the amino groups on the MNP, the presence of N–H (1,640–1,540 cm−1), C–H (3,000–2,830 cm−1) and O–H (3,400–3,100 cm−1) bonding as chemical bonds on the surface of the MNPs was confirmed (Figure
FT-IR spectra of amino- (a), phenyl- (b), carboxy-group modified (c), and original (d) magnetic nanoparticles, respectively.
The zeta-potentials of the nanoparticles were measured by a Zetasizer using the laser Doppler velocimetry technique. For amino group-modified MNP, an isoelectric point was found for ~pH 9.8 (Inverted black triangle points in Figure
Zeta potential of amino- (
In the case of phenyl group-modified MNPs (Ph-MNPs) (White triangle points in Figure
For the phenyl group-modified MNP (Ph-MNP), we could capture the desired molecule chemical interaction. In the previous report, we have successfully achieved selective trapping and detection of aromatic molecules by
Chemical structure of pyriminobac methyl as pesticide (a), nano-PALDI mass spectra of pyriminobac methyl with phenyl group-modified magnetic nanoparticle (b), or original magnetic nanoparticle (c).
The authors thank Professor M. Takagi, Professor K. Ebitani, and Professor Y. Takamura, for providing technical assistance and advice. This research was supported by a WAKATE-B grant from the Japan Society for the Promotion of Science to S. Taira, a Grant-in-Aid to S. Taira from Kinki Innovation Center Japan and from Mitani Foundation for R&D.