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Plasmon-Assisted Enhancement of the Ultraweak Chemiluminescence Using Cu/Ni Metal Nanoparticles Hui Chen, Ruibo Li, Haifang Li, and Jin-Ming Lin* Department of Chemistry, Tsinghua University, Beijing, 100084, China S Supporting Information *

ABSTRACT: Cu/Ni nanoparticles (NPs) with stable fluorescence and excellent water dispersion were synthesized through a facile aqueous solution method with a similar Kirkendall effect. Ultraweak chemiluminescence (CL) from the oxidation reaction between sodium hydrogen carbonate (NaHCO3) and hydrogen peroxide (H2O2) in neutral medium was significantly enhanced by 60 ± 5 nm Cu/Ni NP with a copper and nickel molar ratio of 1:2. The enhancement of the time-dependent CL was dependent on the composition of the NP and the order of reagent addition. On the basis of studies of CL emission spectra, electron spin resonance spectra, UV− vis absorption, and fluorescence spectra, a mechanism of plasmon-assisted metal catalytic effect for this metal NP (MNP)-enhanced CL was proposed. The surface plasmons of MNP can obtain energy from chemical reaction, forming the activated MNP (MNP*), which was coupled to ·OH radical to produce the new adduct ·OH-MNP*. The ·OH-MNP* can accelerate the reaction rate of HCO3− for the generation of emitter intermediate (CO2)2*, which can lead the enhanced CL for the overall reaction.

1. INTRODUCTION Chemiluminescence (CL) is widely used as an analytical tool for its simplicity of detection and the absence of unwanted background luminescence.1,2 However, the CL emission generated during oxidation of inorganic molecules is very weak due to low quantum efficiency. In this regard, enhancement of CL emission is necessary for applications in analytical chemistry. Many compounds or reaction strategies (e.g., catalytic process,3,4 energy transfer,5,6 or redox reactions7,8) have been proposed for an enhanced and amplified CL emission. Nanoparticles (NPs)-based redox catalysts exhibited unique behavior in catalysis because their electrochemical properties differed from those of their bulk phase. Metal NPs (MNPs) with their high density of charge carriers have received much attention in recent years as a novel alternative to catalyze redox CL reactions. Metal-colloid NPs such as Au, Ag, and Pt are excellent catalysts for enhanced CL emission.9−11 The optical properties of MNP dominated by localized surface plasmons are size- and shape-dependent.12 So far, most research has been concerned with preparing different-sized metal-colloid NPs, investigating reaction parameters on CL signal,13 and using spectroscopic methods of analysis to explain the possible mechanisms.14 However Geddes reported that metal surface plasmons can be directly excited by chemically induced electronically excited molecules providing amplified CL emission.15 The excited-state energy of CL is transferred (coupling) to surface plasmons and subsequently © 2012 American Chemical Society

emitted with the identical spectral characteristics of the chemiluminescent species in addition to the uncoupled freespace emission. Low-power microwaves can accelerate the CL reaction by selectively heating of MNP resulting in a significant enhancement of CL.16 The majority of these MNP-enhanced CL studies have focused on the use of nanostructured metal island films deposited onto solid transparent supports. The CL reactions mainly occurred at the interface between multiples phases.17−19 There are two mechanisms contributed to an enhancement effect of MNP: an increase in the local electromagnetic field and an electronic interaction between MNP and reaction species.20 So far, no report has appeared to investigate surface plasmons in a homogeneous MNP-enhanced CL system to the best of our knowledge. In this work, surface-plasmon-assisted enhancement of the ultraweak CL using Cu/Ni metal NPs was found in the reaction of bicarbonate and hydrogen peroxide. The change of the metal surface plasmons peak provided critical information regarding individual particle properties and the reaction kinetics. Cu/Ni NPs catalyzed the CL reaction of HCO3−and H2O2 to produce the emitter (CO2)2*, and the enhanced CL was generated from the surface-plasmons-coupled CL of (CO2)2*. Received: March 31, 2012 Revised: June 23, 2012 Published: June 25, 2012 14796

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Figure 1. Kinetic curves of (a) Cu, (b) Ni, and (c) Cu/Ni NP in the NaHCO3-H2O2 system with the batch method. MNP was injected into the mixture of NaHCO3 and H2O2 solution. (d) Different reagents adding sequences for the CL. MNP was mixed with NaHCO3 solution before H2O2 injection. 1: H2O; 2: Cu; 3: Ni; 4: Cu/Ni NP.

2. EXPERIMENTAL SECTION 2.1. Chemicals. All chemicals used in this experiment were of analytical grade. Hydrogen peroxide (H2O2, 30%) was obtained from Alfa Aesar (Heysham, U.K.). Sodium hydrogen carbonate (NaHCO3), citric acid, and ethylene glycol were purchased from Beijing Chemical Reagent (Beijing, China). Nickel(II) acetate tetrahydrate was obtained from J&K Scientific (Beijing, China). Nano nickel powder and nano copper powder were bought from Hefei Quantum Quelle Nano Science and Technology (Hefei, China). 5,5-Dimethyl-1pyrroline N-oxide (DMPO) was purchased from Tokyo Kasei Kogyo (Tokyo, Japan). 2,2,6,6-Tetramethyl-4-piperidine (TEMP) was obtained from Sigma-Aldrich (St. Louis, MO). All water was freshly deionized using an ultraviolet ultrapure water system (18.3 MΩ·cm, Barnstead). 2.2. Apparatus. Batch CL experiments were carried out with a BPCL luminescence analyzer (Institute of Biophysics, Chinese Academy of Sciences, Beijing, China). The flowinjection (FI) CL signal was measured with a LumiFlow LF800 detector (NITI-ON, Funabashi, Japan) with two peristaltic pumps (SJ-1211, Atto, Tokyo, Japan). Absorption spectra were collected using a UV−vis spectrophotometer (UV-3900, Hitachi, Tokyo, Japan). Emission spectra were measured with a fluorescence (FL) spectrophotometer (F-7000, Hitachi, Tokyo, Japan). Electron spin resonance (ESR) spectra were measured on a Bruker spectrometer (ESP-300 E, Bruker, Karlsruhe, Germany). The X-ray diffraction (XRD) data were collected using a Bruker D8 X-ray diffractometer (Cu Kα radiation, 40 kV, 40 mA, λ = 0.154 nm). X-ray photoelectron spectroscopy (XPS) was carried out on a PHI Quantera SXM

spectrometer with an Al Kα X-ray source (ULVAC-PHI, Chigasaki, Japan). Fourier transform infrared (FTIR) spectrum was recorded on a PerkinElmer 100 FTIR spectrometer (Waltham, Massachusetts, USA). Transmission electron microscopy (TEM) image was recorded by a JEM-1200EX electron microscope operating at 100 kV (JEOL, Tokyo, Japan). 2.3. Synthesis of Copper/Nickel NP. The Cu/Ni NPs were synthesized through a modified method with a similar Kirkendall effect.21 In a typical reaction, nano copper powder (0.50 g) and an appropriate amount of nickel acetate tetrahydrate were dissolved in a solution of 48 mL of ethylene glycol and 12 mL of water. The solutions were added to a three-necked flask and heated to 185 °C under nitrogen flow. Then, 0.1 mol mL−1 citric acid was injected. The solution was refluxed for several hours. The size of Cu/Ni NP was controlled by the amount of nickel acetate tetrahydrate and the refluxing time. In this research, 0.97, 1.30, 1.95, 3.90, 5.80, and 7.80 g of nickel acetate tetrahydrate were used to synthesize different sizes of Cu/Ni NP, respectively. The products were centrifuged and washed with water and ethanol five times for CL measurement. 2.4. MNP-HCO3−-H2O2 CL System. Light-producing reactions were carried out in a glass cuvette with a batch method, and the detection was performed on a BPCL luminescence analyzer. A 100 μL mixture of NaHCO3 and H2O2 (1:1 v/v) was added to the cuvette; then, 100 μL of MNP was injected into the mixed solution by a microliter syringe. The CL intensity was displayed and integrated with 0.1 s interval at −1.2 kV. In a flow system, NaHCO3 and H2O2 in two lines were mixed first by a three-way piece, and then MNP 14797

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HCO3− + H 2O2 ⇌ HCO4 − + H 2O

in another line was introduced to mix with NaHCO3 and H2O2 in a flow cell for the detection. 2.5. CL Spectra Measurements. Two methods were used to measure the CL spectrum of this system. One was using 10 narrow band interference filters to achieve the CL spectrum, which were inserted between the cuvette and the photomultiplier tube (PMT) in the batch experiments. The other was performed by a Hitachi F-7000 spectrophotometer with a flow analysis apparatus when the Xe lamp was turned off. The width of the emission slit was opened to 20 nm during the recording of CL spectra. All optical measurements were performed at room temperature. 2.6. ESR Experiments. ESR spectra were recorded at room temperature using a Bruker ESP-300 E spectrometer (microwave power 1.0 mW, modulation amplitude 1 G). A 10 μL sample solution for the ESR measurement was loaded into a 50 μL quartz micropipet. All spectra were recorded 1 min after the addition of the oxidant.

(1)

HCO4−

is a reactive oxygen species and easily decomposes to generate hydroxide radical (·OH) and superoxide ion radical (·O2−) (reactions 2−4). HCO4 − → · CO3− + ·OH H 2O2 +

·CO3−

→

HCO3−

(2)

+ HO2 ·

(3)

HO2 · → H+ + ·O2−

(4) 1

The singlet oxygen ( O2), singlet oxygen molecular pair [(O2)2*] (reactions 5 and 6), and excited double (CO2)2* (reactions 7 and 8) have been confirmed as the CL emitters.22 HO2 ·+HO2 · → 1O2 + H 2O2

(5)

2·O2− + 2·O2− + 4H 2O → (O2 )2* + 2H 2O2 + 4OH− (6)

·OH +

3. RESULTS AND DISCUSSION 3.1. Characterization of MNP. Cu, Ni, and Cu/Ni NP were used to study the process of the CL from the reaction between NaHCO3 and H2O2. The MNPs were characterized using TEM, XRD, UV−vis, FTIR, FL, and XPS, as described in the Supporting Information. TEM image showed that the average size of prepared Cu/Ni NP is 60 ± 5 nm (molar ratio Cu/Ni 1:2) (Figure S1 in the Supporting Information). XRD indicated that the composite of the Cu/Ni NP was formed (Figure S2 in the Supporting Information). The Cu/Ni NP has a plasmon band at 250−350 nm, located at an intermediate position between the copper and nickel plasmons bands, indicating the formation of a Cu/Ni nanocomposite (Figures S3a in the Supporting Information). The surface hydroxylic groups, which were employed to improve the stability and hydrophilicity of MNP, were qualitatively characterized with FTIR (Figure S3b in the Supporting Information). The position of the fluorescence maximum of Cu/Ni NP located at 565 nm was close to that of Cu NP. The emission wavelength of Ni NP was 630 nm (Figure S3c in the Supporting Information). XPS showed that Cu/Ni NP consisted of Cu, Ni, and O elements. The O element was from the modification of hydroxyl group, which was verified by the binding energy of O 1s detected as 533 eV (Figure S4 in the Supporting Information). A remarkably enhanced ferromagnetic property of Cu/Ni NP was observed from the hysteresis loop (Figure S5 in the Supporting Information). 3.2. Kinetic Aspect. Different adding sequences for the reaction were tested with a batch method to study the kinetic process of the MNP-NaHCO3-H2O2 system. Figure 1a showed the CL process of Cu NP in NaHCO3-H2O2 system. Cu NP was injected about 11 min after the initiation of the NaHCO3H2O2 reaction. The CL intensity had a maximum value of 563 in 0.2 s, which was quenched slowly over about 100 s. For Ni NP injected in the same CL system, the CL intensity had a maximum value of 221 in 0.2 s (Figure 1b). The CL system injected with Cu/Ni NP about 6 min after the initiation of the chemical reaction produced the strongest CL with intensity of 1934 counts obtained in 0.2 s, and it remained for about 200 s before declining to baseline (Figure 1c). The CL of the HCO3−-H2O2 system has been studied in our previous work.22 When H2O2 was injected into NaHCO3 solution, peroxymonocarbonate (HCO4−) was formed (reaction 1).

HCO3−

−

→ OH + ·HCO3

(7)

2·HCO3 → (CO2 )2* + H 2O2

(8)

It was supposed that an active intermediate might be produced in the CL process. The MNP may obtain energy from the CL reaction, and its surface plasmons are excited (MNP*). The activity of MNP* can be indirectly distinguished from the CL intensity. Surface plasmons are the free electrons in metals that collectively oscillate at frequencies similar to that of light. Light from 1O2 in NaHCO3-H2O2 system can excite the surface plasmons to facilitate the generation of CL emitters. The excited MNP* will couple to ·OH and form a new adduct as ·OH-MNP* (reactions 9 and 10). O2 + MNP → 3O2 + MNP*

1

(9)

·OH + MNP* → · OH‐MNP*

(10) −

The ·OH-MNP* will react with HCO3 and thus change the generation rate of emitters intermediate as (CO2)2*. More (CO2)2* will be produced on the surface of MNP (reactions 8 and 11). ·OH‐MNP* + HCO3− → OH− + · HCO3 + MNP* (11)

(CO2)2* is unstable and can decompose to CO2 releasing energy with photon irradiation. The generated light will be greatly enhanced (hvm) by the surface plasmons of the MNP* (reactions 12 and 13). (CO2 )2* → 2CO2 + hv

(12)

hv

MNP* → MNP + hvm

(13)

When Cu, Ni, or Cu/Ni NP was first added to the solution of NaHCO3, then H2O2 solution was injected, the maximum value of CL intensity was 44, 31, and 73, respectively (Figure 1d). The shape of CL curves changed with one peak. Compared with that of the system without MNP in line 1, the CL intensity decreased after the addition of MNP (Figure 1d, lines 2−4). These MNP exhibited an inhibitory effect in the CL system at this adding sequence. The enhanced CL was obtained only when the MNP was injected into the mixing solution of NaHCO3-H2O2. On the basis of the above result, we believe that MNP reacted with H2O2, first reducing the formation of 14798

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interference filters (400−640 nm). As shown in Figure 3a, the CL spectrum of Cu, Ni-, and Cu/Ni NP-enhanced NaHCO3H2O2 system has the same maximum emission wavelength located at 440 nm. It has been reported that the peak at 440 nm may correspond to the decomposition of the excited double (CO2)2*.23 The decomposition energy of (CO2)2 dimer is high enough to promote emission at a wavelength higher than 220 nm. Three different MNP-enhanced CL systems have the same maximum CL emission wavelength, which demonstrated that the enhanced light was related to the NaHCO3-H2O2 system. The enhancement effect was from the MNP. To investigate the change of the emitting species in the total reaction process of different MNP-enhanced CL systems, the CL spectra as shown in Figure 3b−d were measured by an FL spectrometer when the Xe lamp was turned off. All reaction reagents were added to a fluorimeter cell. Results showed that in Cu, Ni, and Cu/Ni NP-enhanced NaHCO3-H2O2 systems, trends of the generation of radicals intermediate, the enhancement of emission, and the ultimate decrease in light occurred at the same wavelength under different reaction time periods. This further demonstrated that the enhanced CL originated from the same mechanism and may be related to the surface plasmons of the MNP. To verify further the possible surface plasmons effect from MNP, the UV−vis absorption spectrum change of the MNP was investigated. When MNP was injected into H2O2 solution, the surface plasmons absorption peak of MNP disappeared (Figure 4a). It indicated that H2O2 reacted with MNP; however, when the MNP was injected into the NaHCO3H2O2 system, the plasmons absorption peak of Cu NP and Ni NP still existed after reaction, but the absorption band of Cu/ Ni NP disappeared after CL reaction (Figure 4b). We attributed this to the change of the surface plasmons of Cu/ Ni NP. During the reaction, the high rate of transfer and coupling of the CL to the surface plasmons changed their electronic structure and weakened the photon absorption of free electrons. It suggested that MNP should be added after the generation of radicals in reaction solution, and adding MNP early would consume the amount of H2O2 without apparent enhancement efficiency. The FL emission wavelength of this CL system with MNP showed no differences between the before and after CL reaction (Figure 5a). The peak located at 540 nm appeared in the FL spectra of the Cu NP-NaHCO3-H2O2 system during the reaction time of 1 to 20 min. The FL intensity increased gradually over the reaction time. The position of the fluorescence maximum was the same as that of Cu NP located at 540 nm, demonstrating that Cu NPs still existed after reaction. The enhanced FL was from the surface plasmons of Cu NP. The emission peak located at 630 nm was the same as that of Ni NP in the FL spectra of the Ni NP-NaHCO3-H2O2 system during the reaction time of 1 to 15 min (Figure 5b). The decreasing FL of system with Ni NP was linked to its anomalous magnetic properties. Figure 5c showed the FL spectra of Cu/Ni NP-NaHCO3-H2O2 system after different reaction time. The emission peaks were located at 565 nm, and the FL intensity was enhanced with the increasing reaction time. The maximal emission wavelength was consistent with that of Cu/Ni NP. It is a metal-enhanced FL. The FL spectra indicated that these MNP could not be oxidized in the CL process of the NaHCO3-H2O2 system. 3.5. Spin Trapping Studies. Room-temperature ESR spectroscopy was used to study the free radical intermediates.

1

O2. The surface plasmons of MNP cannot be excited to facilitate the generation of CL emitters for the enhanced CL. An apparent time-dependent CL was observed from the kinetic curve of Cu/Ni NP-NaHCO3-H2O2 system. As shown in Figure 2, Cu/Ni NP was injected into the NaHCO3-H2O2

Figure 2. Time dependence CL of Cu/Ni NP-NaHCO3-H2O2 system with the batch method. Cu/Ni NP was injected at 1.5, 2.5, 3.0, 6.0, 8.0, and 10 min after the initiation of NaHCO3-H2O2 reaction, respectively.

system at a different time of the reaction. The CL showed an enhancement during the first 1−6 min, then began to decrease. A FI system was set up to investigate the importance of mixing time on the enhanced CL. The result was consistent with that of batch method (Figure S6 in the Supporting Information). 3.3. Effects of Experimental Conditions. Cu/Ni NPs with various compositions and corresponding sizes were investigated in the NaHCO3-H2O2 system. The CL intensity decreased with Cu/Ni NP of high metal molar ratio. Three different sizes of Cu/Ni NP at the concentration range of 0.1− 10 mg mL−1 were added to the NaHCO3-H2O2 system, respectively. A remarkable size effect was observed. The strongest CL was obtained with 60 ± 5 nm Cu/Ni NP (Figure S7a in the Supporting Information). It was found that the CL intensity increased with the concentration of Cu/Ni NP and reached a maximum at the concentration of 1.0 mg mL−1. The CL intensity decreased dramatically at higher concentration. The light self-absorption of Cu/Ni NP, the interparticle magnetic interaction, and the chance of molecule collision were increased at higher concentration, which could lead to the quenching effect. The effect of pH on the CL was studied. The enhanced CL depended on the pH value of the reaction solution. The MNPenhanced CL intensity reached a maximum at pH 7.25. pH relates to the existing state of oxide or catalyst. The highly dispersed oxide or catalyst had more active centers with higher activity in CL process. The CL of Cu/Ni NP-NaHCO3-H2O2 system was found to be easily affected by the solution pH (Figure S7b in the Supporting Information). Cu/Ni NPs accelerate the migration of free electron in the surface, which enhances their activity at transition state. 3.4. Spectra of CL Systems. CL spectrum information on the MNP-enhanced CL was achieved using 10 narrow band 14799

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Figure 3. CL spectra of (a) MNP-NaHCO3-H2O2 system achieved using interference filters. 1: Cu; 2: Ni; 3: Cu/Ni NP. The CL spectra of reaction process of (b) Cu, (c) Ni, and (d) Cu/Ni NP in NaHCO3-H2O2 system recorded by fluorescence spectrometer when Xe lamp was turned off.

Figure 4. (a) Absorption spectra of MNP in H2O2 solution. 1: Ni NP; 2: Cu NP; 3: Cu/Ni NP. (b) Absorption spectra of MNP in NaHCO3-H2O2 system. 1: Cu; 2: Cu/Ni; 3: Ni NP.

TEMP, a specific target molecule of 1O2, can react with 1O2 to give the adduct 2,2,6,6-tetramethyl-4-piperidine-N-oxide (TEMPO). TEMPO is a stable nitroxide radical with a characteristic spectrum.24 Figure 6a (line 1) shows the specific

signal of TEMPO that supported the formation of 1O2 in the NaHCO3-H2O2 system. When TEMP was added to the solution mixture of MNP, NaHCO3, and H2O2, the signal intensity decreased in all systems (Figure 6a, lines 2−4). This 14800

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Figure 5. Fluorescence spectra of (a) Cu NP-NaHCO3-H2O2 system, (b) Ni NP-NaHCO3-H2O2 system, and (c) Cu/Ni NP-NaHCO3-H2O2 system at different reaction time.

Figure 6. ESR spectra of (a) nitroxide radicals generated by reaction of TEMP probe in MNP-NaHCO3-H2O2 system and (b) hydroxide radical addition to DMPO in MNP-NaHCO3-H2O2 system. 1: H2O; 2: Cu; 3: Ni; and 4: Cu/Ni NP in panels a and b. Conditions: Receiver gain: 1.00 ×105; modulation amplitude: 1 G; sweep width: 100.00 G; microwave power: 1.00 × 101 mW.

EPR peaks (Figure 6b, lines 2 and 4). This phenomenon further suggested that ·OH existed and reacted with MNP. The magnetic property of Ni NP inhibited the combination of ·OH with MNP, which further weakened the CL. 3.6. Mechanism of the MNP CL System. The process of the MNP-enhanced CL is shown in Figure 7. The CL spectra indicate that the emitter is originated from the reaction of NaHCO3-H2O2 instead of the MNP. The MNP accelerated the kinetics of the chemical reaction. The absorption spectra proved the importance of adding order of reagents for the enhancement. The enhanced CL could be obtained only when contact interaction between radicals and MNP occurs, which

revealed that singlet oxygen was consumed in the MNPNaHCO3-H2O2 system. MNP accelerated the decomposition of singlet oxygen and increased the formation of other radical intermediates such as ·HCO3. DMPO was used to detect ·OH using ESR spectroscopy. Figure 6b (line 1) presented the signal of DMPO-OH adduct when DMPO was added to the NaHCO3-H2O2 system. The result confirmed the generation of ·OH in the NaHCO3-H2O2 system, but when DMPO was added to the mixture solution of NaHCO3, H2O2, and MNP, we found that only the CL system with Ni NP increased its ESR signal (Figure 6b, line 3), whereas adding Cu and Cu/Ni NPs decreased the intensity of 14801

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Figure 7. Schematic illustration of the possible CL process of the NaHCO3-H2O2 system in the presence of MNP.

Notes

was an apparent property of catalytic mechanism. The MNP still existed after reaction from UV and FL spectra, suggesting that it was a CL resonance energy transfer (CRET) process instead of an absolute catalytic effect. The decrease in 1O2 in ESR spectra indicated the MNP accelerated the loss of excess energy of 1O2 via absorption for exciting its surface plasmons. The decreasing intensity of DMPO-OH adduct proved that the activated MNP could be easy coupled to ·OH radical to form ·OH-MNP* by electron transfer (reactions 9 and 10). The ·OH-MNP* accelerated the reaction of HCO3−and the generation of (CO2)2* (reactions 8, 11, and 12).25,26 Because the wavelength of CL emission and the surface plasmons overlapped, the emission from (CO2)2* was readily induced/ coupled to surface plasmons, amplifying the CL signal (Reaction 13). Therefore, the plasmon-assisted metal catalytic nature of the main mechanisms was responsible for the enhanced CL. The strong light emission may find future applications in a sensitive, simple, and straightforward FI CL analysis method for the determination of hydrogen peroxide in environmental and biological samples.

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by National Natural Science Foundation of China (no. 20935002) and China Postdoctoral Science Foundation (no. 023260207).

■

4. CONCLUSIONS In summary, the MNP-enhanced CL from Cu, Ni, and the prepared Cu/Ni NPs in an aqueous NaHCO3-H2O2 system was observed for the first time. The strongest CL intensity was obtained from the Cu/Ni NP. The enhanced CL was timedependent, and it was restricted by the adding order of reagents. A mechanism of plasmon-assisted metal catalysis was proposed for the MNP-enhanced CL. The enhanced CL system opens up new opportunities for its potential application in the detection of H2O2.

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ASSOCIATED CONTENT

S Supporting Information *

TEM images of Cu/Ni NP with different size; XRD data, UV− vis absorption, FTIR, FL spectra, and XPS data of Cu, Ni and Cu/Ni NP; magnetization curves of Ni and Cu/Ni NP; flowinjection experiments; and size effect and pH effect of Cu/Ni NP in NaHCO3−H2O2 system. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

(1) Nieman, T. Chemiluminescence: Theory and Instrumentation, Overview. In Encyclopedia of Analytical Science; Academic Press, Orlando, FL, 1995. (2) Giokas, D. L.; Vlessidis, A. G.; Tsogas, G. Z.; Evmiridis, N. P. TrAC, Trends Anal. Chem. 2010, 29, 1113−1126. (3) Wang, Z.; Liu, F.; Lu, C. Chem. Commun. 2011, 47, 5479−5481. (4) Yang, L.; Guan, G.; Wang, S.; Zhang, Z. J. Phys. Chem. C 2012, 116, 3356−3362. (5) Bi, S.; Zhao, T.; Luo, B. Chem. Commun. 2012, 48, 106−108. (6) Zhao, S.; Liu, J.; Huang, Y.; Liu, Y.-M. Chem. Commun. 2012, 48, 699−701. (7) Xue, W.; Lin, Z.; Chen, H.; Lu, C.; Lin, J.-M. J. Phys. Chem. C 2011, 115, 21707−21714. (8) Lin, Z.; Xue, W.; Chen, H.; Lin, J.-M. Anal. Chem. 2011, 83, 8245−8251. (9) Tian, D.; Zhang, H.; Chai, Y.; Cui, H. Chem. Commun. 2011, 47, 4959−4961. (10) Li, N.; Wang, W.; Tian, D.; Cui, H. Chem. Commun. 2010, 46, 1520−1522. (11) Duan, C. F.; Cui, H. Chem. Commun. 2009, 45, 2574−2576. (12) Kelly, K. L.; Coronado, E.; Zhao, L. L.; Schatz, G. C. J. Phys. Chem. B 2003, 107, 668−677. (13) Kwon, M. J.; Lee, J.; Wark, A. W.; Lee, H. J. Anal. Chem. 2012, 84, 1702−1707. (14) Li, Q.; Liu, F; Lu, C.; Lin, J.-M. J. Phys. Chem. C 2011, 115, 10964−10970. (15) Aslan, K.; Geddes, C. D. Chem. Soc. Rev. 2009, 38, 2556−2564. (16) Aslan, K.; Malyn, S. N.; Geddes, C. D. J. Am. Chem. Soc. 2006, 128, 13372−13373. (17) Weisenberg, M.; Zhang, Y.; Geddes, C. D. Appl. Phys. Lett. 2010, 97, 133103. (18) Mayer, K. M.; Hafner, J. H. Chem. Rev. 2011, 111, 3828−3857. (19) Wang, Y.; Dostalek, J.; Knoll, W. Anal. Chem. 2011, 83, 6202− 6207. (20) Barbillon, G.; Ou, M.; Faure, A. C.; Marquette, C.; Bijeon, J. L.; Tillement, O.; Roux, S.; Perriat, P. Gold Bull. 2008, 41, 174−186. (21) Chen, H.; Lin, L.; Lin, Z.; Guo, G.; Lin, J.-M. J. Phys. Chem. A 2010, 114, 10049−10058. (22) Yin, Y.; Rioux, R. M.; Erdonmez, C. K.; Hughes, S.; Somorjai, G. A.; Alivisatos, A. P. Science 2004, 304, 711−714.

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Corresponding Author

*E-mail: [email protected]. Phone/Fax: +86-1062792343. 14802

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(23) Bollyky, L. J. J. Am. Chem. Soc. 1970, 92, 3230−3232. (24) Villamena, F. A.; Locigno, E. J.; Rockenbauer, A.; Hadad, C. M.; Zweier, J. L. J. Phys. Chem. A 2007, 111, 384−391. (25) Lu, C.; Lin, J.-M. Catal. Today 2004, 90, 343−347. (26) Cordes, H. F.; Richter, H. P.; Heller, C. A. J. Am. Chem. Soc. 1969, 91, 7209−7209.

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