Molecular rectification and conductance switching in carbon-based molecular junctions by structural rearrangement accompanying electron injection

Molecular junctions were fabricated consisting of a 3.7 nm thick layer of nitroazobenzene (NAB) molecules between a pyrolyzed photoresist substrate (PPF) and a titanium top contact which was protected from oxidation by a layer of gold. Raman spectroscopy, XPS, and AFM revealed that the NAB layer was 2-3 molecules thick and was bonded to the two conducting contacts by C-C and N-Ti covalent bonds. The current/voltage behavior of the PPF/NAB(3.7)/Ti junctions showed strong and reproducible rectification, with the current at +2 V exceeding that at -2 V by a factor of 600. The observed current density at +3 V was 0.71 A/cm(2), or about 10(5) e(-)/s/molecule. The i/V response was strongly dependent on temperature and scan rate, with the rectification ratio decreasing for lower temperature and faster scans. Junction conductivity increased with time over several seconds at room temperature in response to positive voltage pulses, with the rate of increase larger for more positive potentials. Voltage pulses to positive potentials and back to zero volts revealed that electrons are injected from the Ti to the NAB, to the extent of about 0.1-1 e(-)/molecule for a +3 V pulse. These electrons cause an activated transition of the NAB into a more conductive quinoid state, which in turn causes an increase in conductivity. The transition to the quinoid state involves nuclear rearrangement which occurs on a submillisecond to several second time scale, depending on the voltage applied. The quinoid state is stable as long as the applied electric field is present, but reverts back to NAB within several minutes after the field is relaxed. The results are interpreted in terms of a thermally activated, potential dependent electron transfer into the 3.7 nm NAB layer, which brings about a conductivity increase of several orders of magnitude.     

Electron transport and redox reactions in carbon-based molecular electronic junctions

A unique molecular junction design is described, consisting of a molecular mono- or multilayer oriented between a conducting carbon substrate and a metallic top contact. The sp2 hybridized graphitic carbon substrate (pyrolyzed photoresist film, PPF) is flat on the scale of the molecular dimensions, and the molecular layer is bonded to the substrate via diazonium ion reduction to yield a strong, conjugated C-C bond. Molecular junctions were completed by electron-beam deposition of copper, titanium oxide, or aluminium oxide followed by a final conducting layer of gold. Vibrational spectroscopy and XPS of completed junctions showed minimal damage to the molecular layer by metal deposition, although some electron transfer to the molecular layer resulted in partial reduction in some cases. Device yield was high (>80%), and the standard deviations of junction electronic properties such as low voltage resistance were typically in the range of 10-20%. The resistance of PPF/molecule/Cu/Au junctions exhibited a strong dependence on the structure and thickness of the molecular layer, ranging from 0.13 ohms cm2 for a nitrobiphenyl monolayer, to 4.46 ohms cm2 for a biphenyl monolayer, and 160 ohms cm2 for a 4.3 nm thick nitrobiphenyl multilayer. Junctions containing titanium or aluminium oxide had dramatically lower conductance than their PPF/molecule/Cu counterparts, with aluminium oxide junctions exhibiting essentially insulating behavior. However, in situ Raman spectroscopy of PPF/nitroazobenzene/AlO(x)/Au junctions with partially transparent metal contacts revealed that redox reactions occurred under bias, with nitroazobenzene (NAB) reduction occurring when the PPF was biased negative relative to the Au. Similar redox reactions were observed in PPF/NAB/TiO(x)/Au molecular junctions, but they were accompanied by major effects on electronic behavior, such as rectification and persistent conductance switching. Such switching was evident following polarization of PPF/molecule/TiO2/Au junctions by positive or negative potential pulses, and the resulting conductance changes persisted for several minutes at room temperature. The "memory" effect implied by these observations is attributed to a combination of the molecular layer and the TiO2 properties, namely metastable "trapping" of electrons in the TiO2 when the Au is negatively biased.     

In situ raman spectroelectrochemistry of electron transfer between glassy carbon and a chemisorbed nitroazobenzene monolayer

In situ Raman spectroscopy was used to monitor 4-nitroazobenzene (NAB) in an electrochemical cell, both as a free molecule and as a chemisorbed monolayer on a glassy carbon (GC) electrode surface. Reduction of free NAB exhibited two well-defined voltammetric couples in acetonitrile, and the accompanying spectral changes supported a mechanism involving two successive 1-e(-) transfers. Raman spectra of NAB chemisorbed to GC via diazonium ion reduction were obtained in acetonitrile with a high-sensitivity, line-focused CCD spectrometer. The chemisorbed NAB spectra were quite different from the free NAB spectra, and were sufficiently strong to monitor as a function of applied potential. In the potential range of +400 to -800 mV vs Ag/Ag(+), the intensity of the Raman bands associated with the phenyl-NO(2) moiety varied, implying an electronic interaction between the pi system of the graphitic substrate and the chemisorbed NAB molecules. Negative of -800 mV, a 1-e(-) voltammetric reduction peak was observed, which was reversible on the positive voltage scan. This peak was accompanied by significant spectral changes, particularly the loss of the N=N and NO(2) stretches. The spectra are consistent with formation of a quinoid structure containing a C=C double bond between the NAB and the graphitic surface. The electron transfer and spectral changes occurred over a wider potential range than expected for a conventional Nernstian equilibrium, but did not appear to be broadened by slow electron-transfer kinetics. The results imply a significant perturbation of electron transfer between the GC and the monolayer, caused by strong electronic coupling between the graphitic pi system and the NAB orbitals. Rather than a discrete electron transfer to a free molecule, the electron transfer to chemisorbed NAB is more gradual, and is presumably driven by the electric field at the electrode/solution interface.     

Gas phase synthesis of Au clusters deposited on titanium oxide clusters and their reactivity with CO molecules

Titanium oxide clusters were formed in the gas phase by the laser ablation of a Ti rod in the presence of oxygen in a He gas. Not only stoichiometric but also nonstoichiometric titanium oxide clusters, Ti(n)O(2n+x)(+) (n = 1-22 and x = -1-3), were formed. The content of oxygen atoms depends strongly on a partial pressure of oxygen. Gold clusters, Au(m) (m = 1-4), were generated by the laser ablation, which were then deposited on Ti(n)O(2n+x) clusters. The formation of Au(m)Ti(n)O(2n+x)(+) follows electron transfer from Au(m) to Ti(n)O(2n+x)(+). The reactivity of Au(m)Ti(n)O(2n+x)(+) cluster ions with CO was examined for different m, n, and x by the mass spectrometry. It was found that Au(m) on Ti(n)O(2n-1)(+) are less reactive than those on the other Ti(n)O(2n+x)(+) (x = 0 and 1). In addition, the reactivity is highest when Au(m) (m = 1 and 3) is on the stoichiometric titanium oxide (x = 0), whereas the reactivity is also high when Au(2) is on the oxygen-rich titanium oxide (x = 1). The reactivity was found to relate to geometrical structures of Au(m)Ti(n)O(2n+x)(+), which were studied by density functional calculations.     

Oxide and carbide formation at titanium/organic monolayer interfaces

X-ray photoelectron spectra (XPS) are reported from a series of buried titanium/organic monolayer interfaces accessed through sample delamination in ultrahigh vacuum (UHV). Conventional characterization of such buried interfaces requires ion-mill depth profiling, an energetic process that frequently destroys bonding information by chemically reducing the milled material. In contrast, we show that delaminating the samples at the metal/organic interface in vacuum yields sharp, nonreduced spectra that allow quantitative analysis of the buried interface chemistry. Using this UHV delamination XPS, we examine titanium vapor deposited onto a C18 cadmium stearate Langmuir-Blodgett monolayer supported on Au, SiO2, or PtO2 substrates. Titanium is widely used as an adhesion layer in organic thick film metallization as well as a top metal contact for molecular monolayer junctions, where it has been assumed to form a few-atoms-thick Ti carbide overlayer. We establish here that under many conditions the titanium instead forms a few-nanometers-thick Ti oxide overlayer. Both TiO2 and reduced TiOx species exist, with the relative proportion depending on oxygen availability. Oxygen is gettered during deposition from the ambient, from the organic film, and remarkably, from the substrate itself, producing substrate-dependent amounts of Ti oxide and Ti carbide "damage". On Au substrates, up to 20% of the molecular-monolayer carbon formed titanium carbide, SiO2 substrates approximately 15%, and PtO2 substrates <5%. Titanium oxide formation is also strongly dependent on the deposition rate and chamber pressure.     

SEM and AES depth profile studies of thin titanium and titanium oxide films covered by nanoscale evaporated Au layers

Thin titanium and titanium oxide films, both covered by ultra-thin gold layers, have been compared with titanium films after analysis, using a combination of SEM and AES. The Ti films were prepared under UHV conditions by evaporation on a glass substrate. The Ti oxide layers were prepared in situ by precisely controlled oxygen sorption at 298 K on Ti film. Both Ti and Ti oxide films were then covered in situ by a very thin Au layer. Analysis was performed in a separate system after long-term exposure of the films to air. SEM analysis revealed a much smaller size grain on the Au coated Ti films than on Ti films not coated with a Au layer. The thin gold layers covering the Ti surface prevent an extensive air interaction with Ti film. The analysis of the features of the Ti Auger spectra during the sputter profile measurements allow to characterise the chemical nature of Ti-oxide formed in Ti/Au interface region. Received: 7 September 1998 / Revised: 14 January 1999 / Accepted: 2 February 1999     

氧化钛纳米管阵列制备及形成机理

采用电化学阳极氧化法在HF水溶液体系使纯钛表面形成一层结构规整有序的高密度TiO2纳米管阵列,考察了几种主要的实验参数（阳极氧化电压、温度、时间、电解液浓度）对TiO2纳米管阵列形貌和尺寸的影响.结果表明,阳极氧化电压是影响氧化钛形貌和纳米管尺寸的最主要因素,而温度和电解液浓度只影响TiO2纳米管阵列形成的时间.对TiO2纳米管阵列进行X射线衍射（XRD）和扫描电子显微镜（SEM）的分析,初步表征了TiO2纳米管阵列的电学性质.并讨论了TiO2纳米管的形成机理.     

Synthesis of TiO2 nanoparticles on the Au(111) surface

The growth of titanium oxide nanoparticles on reconstructed Au(111) was investigated by scanning tunneling microscopy and x-ray photoelectron spectroscopy. Ti was deposited by physical-vapor deposition at 300 K. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. The titanium oxide nanoclusters were synthesized by subsequent exposure to O(2) at 300 K. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from 600 to 900 K. At the same time, the Au(111) surface assumes a serrated 110-oriented step-edge morphology suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of the titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to 900 K results in the formation of stoichiometric TiO(2) nanocrystals as judged by the Ti(2p) binding energies measured in the x-ray photoelectron data. The nanodispersed TiO(2) on Au(111) is an ideal system to test the various models proposed for the enhanced catalytic reactivity of supported Au nanoparticles.     

Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers

Gold-coated fused-silica electrospray (ES) emitters based on vapor-deposited adhesion layers of titanium have been manufactured to investigate the possibilities of producing durable ES emitters applicable in chip-based analytical devices. The stabilities of the emitters were studied by both electrospray and electrochemical experiments and a marked increase in the emitter lifetime, compared to that for Cr/Au coated emitters, was found for the Ti/Au emitters in the ES durability tests. This indicates that Ti (rather than Cr) adhesion layers should be used in association with large-scale fabrication of ES emitters by vapor-deposition techniques. The lifetime of about 500-700 hours also allowed the Ti/Au-coated emitter to be used as an integrated part of a capillary liquid chromatography column coupled to a mass spectrometer in a series of LC/MS experiments. The Ti/Au coating was further studied by electrochemical techniques and scanning electron microscopy in conjunction with X-ray spectroscopy. It is shown that the eventual failure of the Ti/Au emitters in ES experiments was due to an almost complete detachment of the gold layer. Experimental evidence suggests that the detachment of the gold coating was due to a reduced adhesion to the titanium layer during oxidation in positive electrospray. Most likely, this was caused by the formation of an oxide layer on the titanium film. It is thus shown that unlimited emitter stabilities are not automatically obtained even if the metallic adhesion layer is stabilized by an oxide formation under positive electrospray conditions.     

Surface analysis of titanium based biomaterials

The objective of the present study was the defined preparation and characterization of various oxide layers on titanium, Ti6Al7Nb and Ti6Al4V. Immobilization techniques for collagen and hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, the main components contacting an implant within the human body, were tested. The oxide layers were created by electrochemical polarization in phosphate buffer solutions. The thickness of the layers depended on the formation potential. We found a thickness/potential relation of approximately 2.2 nm/V. At formation potentials up to 80 V anatase was the only titanium dioxide modification traceable by Raman spectroscopy and XRD. The electrochemically assisted deposition of hydroxyapatite on these surfaces starts with an amorphous product which can be monitored by SEM, IR and Raman spectroscopy. The immobilization of collagen followed by anodic electrochemical polarization results either in partial integration of collagen fibrils into the oxide layer or at least in a strong increase of the interaction force between TiO₂ and the collagen fibrils.     

Changes in electronic structure upon lithium insertion into the A-site deficient perovskite type oxides (Li,La)TiO3

Investigation on variation of the electronic structure accompanying the electrochemical lithium insertion into the perovskite type oxide, (Li,La)TiO3, has been carried out by X-ray absorption spectroscopy (XAS). During the electrochemical lithium insertion, titanium ion reduced its oxidation state from Ti4+ to Ti3+, while La3+ does not contribute to the reduction reaction resulting from Ti K-edge and La L3-edge XAS, respectively. Furthermore, O K-edge XAS showed marked spectral changes with electrochemical lithium insertion, indicating the electronic structure around oxide ion affected by lithium insertion reaction. From the XAS measurement, we have concluded the variation observed in O K-edge XAS was related to the strong interaction with inserted Li ion. To confirm this, first-principles band calculations were performed for the perovskite structure before and after electrochemical lithium insertion. The calculated results showed that the electron originated from inserted Li transferred to neighboring oxide ion locally as well as to Ti ion. This may be due to local neutralization effect of Li to reduce the electrostatic interaction in the crystal.     

Au改性纳米TiO2材料对NPE-10光催化降解的活性

以钛酸四丁酯和氯金酸为原料，通过溶胶凝胶法制备了Au掺杂的纳米TiO2光催化剂粉体，并用 XRD， BET，XPS和固体紫外可见吸收光谱等技术对其晶相结构，比表面积，表面组成及紫外可见光响应范围进行了表征，对其光催化降解非离子表面活性剂壬基酚聚氧乙烯醚（NPE-10）的活性进行了考察. 结果表明，掺杂的Au在纳米TiO2粉体材料中可能以两种形态存在，即以Au3+离子形式替代Ti4+进入TiO2晶格和以Au原子态形式暴露于粉体表面.前者使TiO2在480～650 nm出现了更强的光吸收，并大大地增强了粉体表面对氧物种的吸附；后者中处于表面原子态的Au又会成为光生电子的受体，有效地避免了光生电子空穴对的复合. 通过对掺杂量及处理温度的优化，在nAu3+/nTi4+=0.005， 500 ℃煅烧的条件下可以制得具有较高的光催化活性的Au/TiO2粉体. 对NPE-10的光催化氧化试验显示，日光照射4小时后降解效率可以达到91.8%；而用未改性的纳米TiO2，在同样条件下，NPE-10的光催化降解效率仅能达到50.2%，商品Degussa P-25也只能达到66%.     

Amino group position dependent orientation of self-assembled monomolecular films of tetraaminophthalocyanatocobalt(II) on Au surfaces

Self-assembled monomolecular films of 1,8,15,22-tetraaminophthalocyanatocobalt(II) (4alpha-CoIITAPc) and 2,9,16,23-tetraaminophthalocyanatocobalt(II) (4beta-CoIITAPc) on Au surfaces were prepared by spontaneous adsorption from solution. These films were characterized by cyclic voltammetry and Raman spectroscopy. Both the surface coverage (Gamma) and intensity of the in-plane stretching bands obtained from Raman studies vary for these monomolecular films, indicating different orientations adopted by them on Au surfaces. The 4alpha-CoIITAPc-modified electrode exhibits an E1/2 of 0.35 V, while the 4beta-CoIITAPc-modified electrode exhibits an E1/2 of 0.19 V, corresponding to the CoII/CoIII redox couple in 0.1 M H2SO4. The Gamma estimated from the charge associated with the oxidation of Co(II) gives (2.62 +/- 0.10) x 10-11 mol cm-2 for 4alpha-CoIITAPc and (3.43 +/- 0.14) x 10-10 mol cm-2 for 4beta-CoIITAPc. In Raman spectral studies, the intensity ratio between in-plane phthalocyanine (Pc) stretching and the Au-N stretching was found to be 6.6 for 4beta-CoIITAPc, while it was 1.6 for 4alpha-CoIITAPc. The obtained lower Gamma and intensity ratio values suggest that 4alpha-CoIITAPc adopts nearly a parallel orientation on the Au surface, while the higher Gamma and intensity ratio values suggest that 4beta-CoIITAPc adopts a perpendicular orientation. The electrochemical reduction of dioxygen was carried out using these differently oriented Pc's in phosphate buffer solution (pH 7.2). Both the Pc's catalyze the reduction of dioxygen; however, the 4alpha-CoIITAPc-modified electrode greatly reduces the dioxygen reduction overpotential compared to 4beta-CoIITAPc-modified and bare Au electrodes.     

All-carbon molecular tunnel junctions

This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V <30%). These all-carbon devices exhibit current density-voltage (J-V) behavior similar to those with metallic Cu top contacts. However, the all-carbon devices display enhanced stability to bias extremes and greatly improved thermal stability. Completed carbon/nitroazobenzene(NAB)/carbon junctions can sustain temperatures up to 300 °C in vacuum for 30 min and can be scanned at ±1 V for at least 1.2 × 10(9) cycles in air at 100 °C without a significant change in J-V characteristics. Furthermore, these all-carbon devices can withstand much higher voltages and current densities than can Cu-containing junctions, which fail upon oxidation and/or electromigration of the copper. The advantages of carbon contacts stem mainly from the strong covalent bonding in the disordered carbon materials, which resists electromigration or penetration into the molecular layer, and provides enhanced stability. These results highlight the significance of nonmetallic contacts for molecular electronics and the potential for integration of all-carbon molecular junctions with conventional microelectronics.     

Photocatalytic oxidation of propylene with molecular oxygen over highly dispersed titanium, vanadium, and chromium oxides on silica

Photocatalytic oxidation of propylene with molecular oxygen at room temperature was investigated over various silica-supported metal oxides with low loading. The photocatalytic active site is assumed to be the isolated tetrahedrally coordinated metal oxides in the ligand-to-metal charge-transferred state, such as (Mdelta- -OLdelta+). Photocatalytic epoxidation of propylene into propylene oxide was promoted over silica-supported V and Ti oxides at steady state. Over silica-supported Cr oxide, the propylene oxide formation rate was remarkably decreased with the time course in the reaction. The oxidation state and the coordination environment of the supported Ti, V, and Cr oxide species were determined by diffuse reflectance UV-vis spectroscopy (DRS) and electron spin resonance (ESR). During the photocatalytic oxidation, the oxidation state of the Ti4+ species was not varied. On the other hand, the V5+ species was partially reduced to V4+ and the Cr6+ species was successively reduced to Cr5+ and Cr3+. An isotopic tracer study of the C3H6-18O2 reaction suggests the difference of the active oxygen species between TiO2/SiO2 and V2O5/SiO2. The active oxygen species on TiO2/SiO2 is derived from molecular oxygen. On the other hand, the photogenerated products on V2O5/SiO2 incorporate the lattice oxygen of the surface metal oxide species. It is suggested that the kinds of terminal ligand (hydroxyl or oxo) of the tetrahedrally coordinated metal oxides on silica decide the active oxygen species in the photocatalytic oxidation. A photoinduced hole center on the monohydroxyl (SiO)3Ti-OH species activates molecular oxygen that reacts with propylene. In the case of the monooxo (SiO)3V=O and dioxo (SiO)2Cr=O2 species, the photoactivated lattice oxygen (OL-) directly reacts with propylene.     

Electrochemical metal deposition on top of an organic monolayer

Electrochemical deposition of metals (platinum or gold) only on top of an organothiolate, 1,4-benzenedimethanethiol (BDMT) or hexanedithiol (HDT), self-assembled monolayer (SAM) on a Au(111) substrate was achieved by electrochemical reduction of PtCl(4)(2-) or AuCl(4)(-) ion, which was preadsorbed on one free thiol end group of the dithiol SAM formed on a Au surface, in a metal-ion-free sulfuric acid solution at potentials more negative than the reduction potential of the metal ion. Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) measurement after the reduction of preadsorbed PtCl(4)(2-) ion on BDMT/Au(111) electrode showed the presence of Pt not underneath but on top of the BDMT SAM. After a negative potential scan of the Pt/BDMT/Au(111) electrode to -1.30 V in 0.1 M KOH solution, a typical cyclic voltammogram of a clean Au(111) electrode was obtained, showing that the BDMT SAM with a Pt layer was reductively desorbed. These results proved that a Pt-BDMT SAM-Au substrate sandwich structure without a short circuit between the two metals was successfully constructed by this technique. Furthermore, a decanethiol (DT) monolayer was constructed on a Au layer, which was formed by the reduction of preadsorbed AuCl(4)(-) ion on HDT/Au(111) electrode. The formation of DT/Au/HDT/Au(111) structure was confirmed as two cathodic peaks corresponding to reductive desorption of DT from Au on top of the HDT/Au(111) at -0.97 V and that of Au/ HDT from Au(111) at -1.12 V were observed when potential was scanned negatively to -1.35 V.     

利用钛保护层在ITO电极上直接制备大面积的超薄氧化铝膜

通过磁控溅射并引入钛保护层, 利用在0.3 mol·L^-1硫酸中20 V电压下二次阳极氧化, 在氧化铟锡(ITO)导电玻璃衬底上直接制备了超薄(约140 nm, 为阳极氧化前Al厚度的一半)、大面积(约4 cm²)的多孔阳极氧化铝(AAO). 扫描电子显微镜结果表明生成的微孔与衬底垂直, 孔径和孔间距分别约为30和60 nm. 我们发现钛保护层的作用是提高了Al层的附着性并且防止ITO被腐蚀, 在此体系中钛不能被其它的金属如铬、金、银或铜代替. 紫外-可见光谱透过率结果显示在阳极氧化过程中Ti被氧化成为透明的TiO₂, 利用10-20 nm的钛保护层以及二次阳极氧化过程, 能够保证高透明度. 在ITO上直接制备的这种透明、有序的AAO纳米结构在光子学、光伏领域和纳米制备等方面具有潜在应用.     

Cobalt oxide electrodeposition on various electrode substrates from alkaline medium containing Co–gluconate complexes: a comparative voltammetric study

A study regarding the electrodeposition of Co oxides from alkaline medium containing 12?mM gluconate ligand and 12?mM Co²⁺ on glassy carbon, Au, Pt, Ni, Ti and ITO electrode substrate was carried out through cyclic voltammetry technique. Films of cobalt oxides were deposited either anodically by voltage cycling (100?mV?s^?1) between ?0.3 and 0.6?V (SCE) or by potentiostatic conditions at potential comprised between 0.2 and 0.6?V for a fixed time of deposition. Analysis of the voltammetric experimental data clearly showed that the rate of cobalt oxide electrodeposition process decreases in the order Au > Pt > GC, Ni > Ti, ITO and the massive cobalt electrodeposition does not proceed to an appreciable extent until potentials of 0.3–0.4?V (SCE) is reached. The effect of the scan rate on the peak potential, peak current, and peak-to-peak separation of the deposited cobalt oxide films was studied, and some substantial differences in terms of electrochemical behaviour in relation at the specific substrate electrode were observed and critically discussed.     

丙烯在Au/TiO2催化剂上的化学吸附与临氢环氧化反应

环氧丙烷;丙烯环氧化;丙烯在Au/TiO2催化剂上的化学吸附与临氢环氧化反应     

铁氧化物/金磁性核壳纳米粒子的制备及其富集与SERS研究

本文用种子生长法制备铁氧化物/金磁性核壳纳米粒子, 并利用SERS对其磁场靶向性进行了检测.