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【期刊论文】Size dependence of specific power absorption of Fe3O4 particles in AC magnetic field
顾宁, Ming Ma, Ya Wu, Jie Zhou, Yongkang Sun, Yu Zhang, Ning Gu*
Journal of Magnetism and Magnetic Materials 268(2004)33-39,-0001,():
-1年11月30日
The specific absorption rate (SAR) values of aqueous suspensions of magnetite particles with different diameters varying from 7.5 to 416nm were investigated by measuring the time-dependent temperature curves in an external alternating magnetic field (80kHz, 32.5kA/m). Results indicate that the SAR values of magnetite particles are strongly size dependent. For magnetite particles larger than 46nm, the SAR values increase as the particle size decreases where hysteresis loss is the main contribution mechanism. For magnetite particles of 7.5 and 13nm which are superparamagnetic, hysteresis loss decreases to zero and, instead, relaxation losses (Neel loss and Brownian rotation loss) dominate, but Brown and Neel relaxation losses of the two samples are all relatively small in the applied frequency of 80kHz.
Magnetite particles, Specific power absorption, Size dependence, Hyperthermia, Hysteresis loss, Neel relaxation, Brown relaxation
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【期刊论文】Pendant thiol groups-attached Pd(II) for initiating metal deposition
顾宁, Lina Xua, b, *, Jianhui Liaoa, Lan Huanga, Ning Gua, Haiqian Zhanga, Juzheng Liub
Applied Surface Science 211(2003)184-188,-0001,():
-1年11月30日
A new activation method has been developed for initiating electroless metal deposition on silicon substrates without SnCl2 sensitization and roughening condition. Silicon wafers are first coated with thiol-terminated self-assembled monolayers (SAMs), and then catalyzed with a stable tin-free Pd(II)-based colloidal solution. Atomic force microscopy (AFM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to characterize the step-by-step surfaces and study the binding mechanism of Pd(Ⅱ) with SAMs onto surfaces. Results show that Pd(II) oligomer particles are chemisorbed on pendant thiol surfaces through S-Pd bonds. This process involves fewer steps than the conventional Sn/Pd combined activation one. Furthermore, the chemical bound initiator possesses longevity and can be stored for a long time before metallization.
Pd(, Ⅱ), , SAMs, Electroless plating
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【期刊论文】Synthesis and characterization of titania-coated Mn-Zn ferrite nanoparticles
顾宁, Ming Ma, Yu Zhang, Xiaobo Li, Degang Fu, Haiqian Zhang, Ning Gu*
M. Ma et al./Colloids and Surfaces A: Physicochem. Eng. Aspects 224(2003)207-212,-0001,():
-1年11月30日
A novel core-shell structured composite, titania (TiO2) coated Mn-Zn ferrite nanoparticle, was prepared byhydrolysis of titanium (Ⅳ) chloride (TiCl4) in the presence of Mn-Zn ferrite nanoparticles synthesized with stearic acid gel method. The obtained samples were characterized by energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results show that spinel structural Mn-Zn ferrite nanoparticles (6 nm average diameter) or their aggregates are coated by TiO2 nanoshell with anatase structure for annealed sample. The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate the reduction of the magnetization of the TiO2 coated Mn-Zn ferrite nanoparticles compared with the uncoated ferrite nanoparticles. High coercivity also shows that the prepared uncoated and coated ferrite nanoparticles are not superparamagnetic.
Mn-Zn ferrite nanoparticles, Core-shell structure, Titania-nanocoating
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顾宁, Yu Zhanga, b, *, Xin Wangb, Ming Mab, Degang Fub, Ning Gub, Juzheng Liub, Zuhong Lub, Yi Maa, Ling Xua, Kunji Chena
Applied Surface Science 205(2003)256-261,-0001,():
-1年11月30日
Hyper-Rayleigh scattering (HRS) or incoherent second harmonic generation (SHG) technique has been used to investigate the second-order optical nonlinearities of nanoparticles and seems sensitive to nanoparticle surfaces. Here, more direct evidence that shows the importance of surfaces for HRS response of nanoparticles was experimentally obtained. Two CdS nanoparticles of 3 nm average diameter with different surface-capping molecules, CdS/AOT-SO3- (AOT-SO3- is anion of bis (2-ethylhexyl) sulfosuccinate, disodium salt) and CdS/Py/AOT-SO3- (Py represents pyridine molecule), were studied by HRS technique. The "per particle" first-order hyperpolarizability β values were evaluated to be 3.98×10-27 esu for the CdS/AOT-SO3- and 2.63×10-27 esu for the CdS/Py/AOT-SO3- nanoparticles. A reduction in β value is found when AOT-SO3- on CdS nanoparticle surface is replaced by pyridine. Similarly, the reduction of HRS signal intensity of a solution containing the CdS/AOT-SO3- nanoparticles was observed when increasing pyridine concentration in the solution. Furthermore, the dynamic process of the surface-capping molecule exchange was studied by detecting both HRS signal intensity and electroconductivity variations with time. Possible effect mechanism is discussed in terms of a two-level model approximation derived from molecular chromophores, when considering the influence of different surface-capping molecules on the polarity of Cd-S bonds at nanoparticle surfaces.
CdS nanoparticles, Surface modification, Hyper-Rayleigh scattering
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【期刊论文】DNA Assembly on 2-Dimensional Array of Colloidal Gold
顾宁, Cunwang Ge, , Jianhui Liao, Yihong Wang, Kunji Chen, and Ning Gu.
,-0001,():
-1年11月30日
The primary object of this contribution is to self-assemble DNA on 2-dimensional array of 1-dodecanethiol-encapsulated colloidal gold (2-DACG). The 2-DACG film was deposited by Langmuir-Blodgell (LB) technique. Through phase transfer of aqueous colloidal gold particles into ethanol solutions containing 1-dodecanethiol, the hydrophobic gold colloidal nanoparticles were accomplished. In the presence of traces of 1-dodecanethiol, the gold nanoparticels were transferred via LB technique to a freshly cleaned gold electrode and 2-DACG of close-packed, ordered monolayer was obtained. The 2-DACG was then used as a substrate for the immobilization of DNA under a controled potential of 0.20V vs. saturated calomel electrode (SCE). The properties of 2-DACG before and after the DNA assembly were investigated by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), cyclic voltaininetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that 2-DACG deposited by LB technique was suitable as a substrate for DNA self-assembly.
DNA assembly,, 2-dimensional array,, thiol encapsulated colloidal gold,, substrate
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