A New Method for Identifying Compounds by Luminescent Response

ARTICLE pubs.acs.org/ac

A New Method for Identifying Compounds by Luminescent Response Profiles on a Cataluminescence Based Sensor Runkun Zhang, Xiaoan Cao,* Yonghui Liu, and Xiangyang Chang Environmental Science and Engineering Institute, Guangzhou University, 510006, Guangzhou, People’s Republic of China

bS Supporting Information ABSTRACT: Rapid identification of different compounds has been proven to be one of the most dynamic fields in analytical chemistry. Herein, a very simple cataluminescence-sensorbased (CTL-based) method suitable for rapid identification of compounds is reported. The oxidation of analytes was catalyzed in a closed reaction cell (CRC) containing enough air to facilitate complete luminescent response profiles with several peaks. The multipeaked response profiles are characteristic of analytes and can be used for identifying compounds. In existing CTL-based sensors, CTL reactions take place in an airstream flow reaction cell (AFRC) in which a continuous airstream carries the analytes flow across the catalyst’s surface. The luminescent response profiles obtained are transitory and lack characteristic features, so they cannot be used to identify different compounds. To illustrate the new method, 12 medicines and 4 organic gases were examined in CRC sensors. Results showed that these compounds could be successfully identified through their unique luminescent response profiles. The response was rapid and the system was inexpensive and easy to handle. We believe that it has great potential for real-world use.

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ethods for simple, rapid identification of compounds are urgently needed for the evaluation of medicines, food, and the environment.1
6 For example, the World Health Organization (WHO) recently estimated that approximately 5%
8% of all medicines on the market are counterfeits. This constitutes a multibillion-dollar international problem for the industry (approximately $75 billion U.S. dollars (USD) in 2010).1 Simple methods of identifying medicines are of significant importance to the pharmaceutical industry and the medical field, in addition to their possible uses in other areas. Over the last two decades, a great deal of work has been done toward developing systems that can utilizing cross-reactive sensor arrays in conjunction with pattern recognition methods for online discriminatory analysis.7,8 These systems contain a series of sensing elements in an array format.9,10 At present, changes in the optical, electrochemical, and mass properties of sensors are used to determine the characteristics of the analytes.11
15 The development of cataluminescence (CTL) sensors offers new opportunities for organic analysis, mainly because of the high sensitivity, long-term stability, and simplicity of the CTL sensors.16
22 CTL is a type of chemiluminescence (CL) that is emitted from the surfaces of solid catalysts during catalytic oxidation reactions, yielding excited intermediates in the electronic excited state, which emit luminescence upon falling to the ground state. CTL was first observed by Breysse et al.23 Zhang et al. developed a CTL sensor array with nine sensing elements to recognize alcohols, amines, and thiols.24 Recently, they reported an extended nanomaterial-based CTL sensor array with 21 sensing elements that could be used for the discrimination and identification of flavors in cigarettes.25 r 2011 American Chemical Society

Although sensor array technology has been applied successfully in some areas, multiple sensing elements are not beneficial to the stability of the instrument.26
28 The changes in one of the characteristics of a single sensor over time can affect the final recognition results.29 In addition, most sensor arrays require that every sensor be calibrated before detection.30,31 An identification system that does not require as many sensing elements is urgently needed. A SnO2-semiconductor gas sensor was devised, using dynamic responses from sinusoidal temperature changes. The system can be used to analyze time sequences via fast Fourier transform (FFT) for the identification of several organic gases.32 However, this type of sensor requires bulky equipment, and the process by which it permits the identification gases is relatively complicated.33 Nakagawa et al. developed a single-sensor system for the identification of ethanol and acetone. This system could simultaneously assess CTL spectra using a CCD camera at various temperatures.34 However, this system is still relatively complex and expensive.35 In the common sensors and sensor array technologies mentioned above, samples are introduced into an airstream flow reaction cell (AFRC).11,24,32,33 The interactions between analytes and sensing elements are transitory, which can render useful information unobservable. Our CTL reactions occurred in a closed reaction cell (CRC), instead of in the AFRC. Multipeaked response profiles specific to most compounds were obtained on a single CRC sensor. We were able to identify different compounds Received: July 10, 2011 Accepted: October 21, 2011 Published: October 21, 2011 8975

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Figure 1. Schematic diagram of the cataluminescence (CTL)-based sensor.

by comparing their response profiles. In order to show the utility of this method, the luminescent responses of 12 medicines and 4 organic gases were studied, using CTL sensors in the CRC mode. Possible mechanisms behind the multipeaked response profiles are discussed. Results show that this system can distinguish a wide range of analytes using only one or two sensing units.

’ EXPERIMENTAL SECTION (1). Sensor Fabrication. As shown in Figure 1, the present CTL sensor consisted of three main parts: a laboratory-made reaction cell, a digital temperature controller (Zhihong Electronic Co. Ltd., Beijing, China), and a computerized BPCL ultraweak luminescent analyzer (Model BP-II, Institute of Biophysics, Academia Sinica, Beijing, China). The reaction cell was constructed by placing a cylindrical ceramic heater (Model ZF-35, inner diameter = 4 mm, Ningbo Electric Iron Factory, Ningbo, China) sintered with 0.5-mm-thick layer of nanomaterial (4 mg) in a quartz tube (10 mL). The ceramic heater was kept at the required temperature by a digital temperature controller. Both the inlet and the outlet were equipped with valve switches to allow the reaction cell to be opened (when the system was in AFRC mode) or closed (when the system was in CRC mode). The CTL signal produced by the catalytic reaction was detected and recorded by a photomultiplier tube (Model GDB23, Beijing Nuclear Instrument Factory, Beijing, China). The detection wavelengths were selected over the range of 400
540 nm by changing the interference optical filters with a bandwidth of 24 nm (Institute of Biophysics, Academia Sinica, Beijing, China). (2). Instrumental Analysis for Mechanism Study. In order to determine the mechanism behind CTL emission in the CRC, the outlet of the reaction cell was coupled to an Agilent 7890A GC/MS (Agilent Technologies) equipped with an HP-INNOWax column (30 m, 0.25 mm inner diameter, and 0.25 μm film thickness) for analysis of the reaction products. The reaction time was controlled by turning off the heater and opening the valve switches at the indicated times. A steady airstream was provided by an air pump (Model GA-2600A, Beijing Zhongxing Huili Co. Ltd., Beijing, China). This carried reactants and products away from the catalyst surface. (3). Reagents and Materials. Nano-SrCO3 (purity, g99.99%; average particle size, 15 nm) and nano-ZrO2 (purity, g99.99%; average particle size, 10 nm) were supplied by Shanghai Zhuerna High-Tech Powder Material Co., Ltd. (Shanghai, China). NanoMgO (purity, g99.99%; average particle size, 50 nm) was supplied

by Beijing Nacheng Scientific Trading Co., Ltd. (Beijing, China). Analytical-grade ethyl acetate, vinyl acetate, acetaldehyde, and ether were purchased from Tianjin Damao Chemical Co., Ltd. (Tianjin, China). The details of Western medicines, Chinese medicines, and pharmic solvents are as follows. (a). Western Medicines. Injectable chloramphenicol (CHRL) and metamizole sodium and were purchased from Xinzheng Pharmaceutical Group Co., Ltd. (Tianjin, China). Injectable cefazolin sodium (powder, 0.5 g per vial), cefradine (powder, 0.5 g per vial), and ceftriaxone sodium (powder, 1 g per vial) were supplied by Harbin Pharmaceutical Group Co., Ltd. (Harbin, China). Injectable gentamycin sulfate was purchased from Dongsheng Pharmaceutical Co., Ltd. (Xinxiang, China). Polyinosinic
polytidylin acid (PPA) was supplied by South China Pharmaceutical Group Co., Ltd. (Zhanjiang, China). Injectable benzylpenicillin sodium (powder, 0.5 g per vial) was purchased from Dongfeng Pharmaceutical Group Co., Ltd. (Jiangxi, China). (b). Pharmic Solvents. Injectable lidocaine hydrochloride and sterile water were used as solvents for dissolving powder medicines. Injectable lidocaine hydrochloride (1%, 2 mL per vial) was purchased from Xinzheng Pharmaceutical Group Co., Ltd. (Tianjin, China). Sterile water was supplied by Jiaozuo Pharmaceutical Group Co., Ltd. (Tianjin, China). (c). Chinese Medicines. Shuanghuanglian oral solution was supplied by Harbin Pharmaceutical Group Co., Ltd. (Harbin, China). Its main chemical components are chlorogenic acid, caffeic acid, chrysophanol, physcion, glucose, baicalin, and phillyrin. Yinqiao oral solution was supplied by Guangdong Huanan Pharmaceutical Group Co. Ltd. (Dongguan, China). Its main chemical components include chlorogenic acid, caffeic acid, vitamin C, and glycyrrhizic acid. Huoxiang oral solution was purchased from Longshunrong Pharmaceutical Company (Tianjin, China); liquiritin, glycyrrhizic acid, imperatorin, honokiol, and sinensetin are its chief components. Amino acid oral solution was purchased from Yandong Health Care Co., Ltd. (Dongguan, China). Its main chemical components include tryptophan, tyrosine, phenylalanine, and citric acid. (4). Sample Preparation. The powder medicines were prepared into liquid injections in accordance with the “Instructions for Intramuscular Injection”. The operations were as follows: 0.5 g of benzylpenicillin was dissolved in 2 mL of lidocaine hydrochloride; 1 g of ceftriaxone sodium was dissolved in 3.5 mL of lidocaine hydrochloride; 0.5 g of cefazolin sodium and cefradine were dissolved in 2 mL of sterile water. The liquid medicines (10 μL) were sprayed evenly onto the thick layer of nanomaterials 8976

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Figure 2. Luminescent response profiles of 12 medicines on nano-ZrO2 and nano-MgO surfaces in the CRC, respectively. (Working temperature, 350 °C; detection wavelength, 425 nm. The volume of each of the medicines is 10 μL.)

using a nebullizer, and then the temperature of the ceramic heater was increased to ∼350 °C at a speed of 4 °C s
1. The gas samples were prepared by vaporizing 80 μL of vinyl acetate, 80 μL of ethyl acetate, 100 μL of ether, and 100 μL of acetaldehyde in a 100-mL sample bottle at 90 °C, from which 1 mL was then placed in a 10-mL reaction cell. The final concentration of organic gases was 0.075 g L
1

’ RESULTS AND DISCUSSION (1). Identification of Medicines in the Closed Reaction Cell (CRC). MgO and ZrO2 were chosen as sensing materials, because

they have diverse catalytic activities. The characteristic luminescent response profiles of the 12 medicines on nano-ZrO2 and nano-MgO surfaces are shown in Figure 2. The luminescent response profiles function as the fingerprint of each medicine and, thus, provide information about the differences between the 12 medicines. Facile recognition of these medicines can be achieved from their characteristic luminescent response profiles alone.

As shown in Figure 2, the luminescent response profile of amino acid oral solution on nano-ZrO2 surface lacked characteristic features—it has only one peak. However, marked characteristic features were observed on the nano-MgO surface. The differences in the luminescent response profiles of the Shuanghuanglian and Yinqiao oral solutions on nano-MgO surfaces were not conspicuous. However, the differences between their luminescent response profiles on the nano-ZrO2 surface were very obvious. The Yinqiao oral solution produced four peaks, and the Shuanghuanglian oral solution produced three. The positions and intensity of peaks differed. These results indicate that different analytes produce different luminescent response profiles on different nanomaterials, and that the same nanomaterial can exhibit different luminescent response profiles when exposed to different analytes. It can be concluded that characteristic response profiles of most analytes can be obtained by choosing one or two appropriate catalysts. (2). Idendification of Organic Gases in the CRC. We examined four organic gases: acetaldehyde, ethyl acetate, vinyl acetate, 8977

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Figure 3. Luminescent response profiles of four organic gases on the nano-MgO and nano-SrCO3 surfaces in the CRC, respectively. (Working temperature, 250 °C; detection wavelength, 425 nm. The concentration of each of the gases is 0.075 g L
1.)

Figure 4. Luminescent response profiles of medicines and organic gases in the AFRC: (A) luminescent response profiles of medicines on nano-MgO surface (working temperature, 350 °C) and (B) luminescent response profiles of organic gases on nano-SrCO3 surface (working temperature, 250 °C). (Conditions for both profiles: detection wavelength = 425 nm; airflow rate = 210 mL min
1. The volume of each of the medicines is 10 μL, and the concentration of each of the organic gases is 0.075 g L
1.)

and ether. We found MgO and SrCO3 to have diverse catalytic reactions to gases. They were used for identification of organic gases. The results are shown in Figure 3. As expected, each gas showed a unique luminescent response profile on the surfaces of MgO and SrCO3. Ether produced three peaks on MgO and five peaks on nano-SrCO3. The single luminescent response profile of ether on the MgO or SrCO 3 catalysts is distinct. Although the luminescent response profile of ethyl acetate showed only a single peak on MgO and another on SrCO3, the position and slope of those peaks rendered them distinct from each other. Ethyl acetate could be identified through comparison of the luminescent response profiles on the two catalysts. That is, if the luminescent response profile of a given gas on a certain catalyst surface lacks characteristic features, we can use two catalysts to render the results more reliable. Our experimental results showed no cases of different analytes showing the same luminescent response profiles (including the number of peaks, the peak position, and the peak shape) on two different catalyst surfaces. These results indicate that recognition analysis could be conducted using one or two CTL sensors in most situations.

For practical applications, it would be helpful to collect luminescent response profiles from various compounds on different catalyst surfaces to establish a database of distinct standard profiles. By searching through the database, researchers could recognize unknown samples by comparing their profiles to standards. (3). Comparison of Cataluminescence (CTL) Reactions in the Airstream Flow Reaction Cell (AFRC) and the Closed Reaction Cell (CRC). The CTL reactions of four medicines (Huoxiang oral solution, Yiaoqiao oral solution, injectable chloramphenicol, and injectable gentamycin sulfate) on the nanoMgO surface and four organic gases (acetaldehyde, ethyl acetate, vinyl acetate, and ether) on the nano-SrCO3 surface in the AFRC were studied in order to compare the AFRC to the CRC. As shown in Figure 4, the luminescent response profiles of each analyte are single-peaked and similar. The AFRC was generally used in online quantitative analysis, because the intensity of CTL is proportional to the concentration of analyte.18
22 As mentioned above, when CTL reactions occur in the CRC, the luminescent response profiles show multiple peaks and are characteristic of the analytes. CRC allows the user to identify 8978

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Figure 5. Luminescent response profiles at different concentrations in the CRC: (A) luminescent response profiles of Yinqiao oral solution on a nanoZrO2 surface (working temperature = 350 °C) and (B) luminescent response profiles of vinyl acetate on a nano-SrCO3 surface (working temperature = 250 °C). (Detection wavelength for both profiles is 425 nm.)

Figure 6. Luminescent response profiles at different detection wavelengths in the CRC: (A) luminescent response profiles of Yinqiao oral solution on a nano-ZrO2 surface (working temperature = 350 °C) and (B) luminescent response profiles of vinyl acetate on a nano-SrCO3 surface (working temperature = 250 °C). (For both profiles, the volume of the Yinqiao oral solution is 10 μL and the concentration of the vinyl acetate is 0.075 g L
1.)

most compounds using only one or two sensors and a simple instrument. We can integrate CRCs and AFRCs for qualitative and quantitative analysis. (4). Effects of Concentration. The CTL reactions of Yinqiao oral solution on the nano-ZrO2 surface and of vinyl acetate on the nano-SrCO3 surface were evaluated for several different concentrations. We mixed 1 mL of Yinqiao oral solution with 1, 4, and 9 mL of distilled water. The luminescent response profiles of Yinqiao oral solution on the nano-ZrO2 surface are shown in Figure 5A. Different luminescent response profiles were produced. The number of peaks and the peak intensity of the profiles decreased with decreasing concentration. These results indicate that the method could be applied to determine counterfeit medicines. Because the ingredients of any given medicine are fixed, any change in ingredient concentration can cause a change in the profile. In addition, this system could be used in manufacturing process for quality control purposes. The response profile of vinyl acetate varies with concentration, as shown in Figure 5B. Two peaks were observed at high concentrations. The second peak appeared late at higher concentrations, and the first peak disappeared at low concentrations.

The concentration dependence of the response profiles of these gases limits the wide application of this system in the real world. Nevertheless, it may be useful for quality control in the manufacturing process of various gases. (5). Effects of Detection Wavelength. Luminescent response profiles of Yinqiao oral solution on nano-ZrO2 surface and vinyl acetate on nano-SrCO3 surface were examined at different detection wavelengths. Interference filters of 400, 425, and 490 nm were introduced to detect luminescent response profiles. The results are shown in Figure 6. The effect of detection wavelength on the shape of the luminescent response profile was not obvious. Because intense background signals are not conducive to the stability of the instrument, and because the background signal increases with increasing wavelength, the 425-nm wavelength was selected for analysis in subsequent experiments. (6). Effect of Working Temperature. The CTL reactions of the Yinqiao oral solution on nano-ZrO2 surface and vinyl acetate on nano-SrCO3 surface were examined at different temperatures. Relatively high working temperatures were chosen for the Yinqiao oral solution, to avoid producing carbon soot. Figure 7 shows the luminescent response profiles at different reaction temperatures. 8979

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Figure 7. Luminescent response profiles at different working temperatures in the CRC: (A) luminescent response profiles of Yinqiao oral solution on a nano-ZrO2 surface and (B) luminescent response profiles of vinyl acetate on a nano-SrCO3 surface. (Conditions for both profiles: detection wavelength = 425 nm; volume of the Yinqiao oral solution = 10 μL; concentration of the vinyl acetate = 0.075 g L
1.)

Figure 8. Luminescent response profiles of Yinqiao oral solution and vinyl acetate for time periods from 0 h to 288 h: (A) luminescent response profiles of Yinqiao oral solution on a nano-ZrO2 surface (working temperature = 350 °C) and (B) luminescent response profiles of vinyl acetate on a nanoSrCO3 surface (working temperature = 250 °C). (Conditions for both profiles: detection wavelength = 425 nm; volume of the Yinqiao oral solution = 10 μL; and concentration of the vinyl acetate = 0.075 g L
1.)

Temperature was found to exert a considerable effect on the luminescent response profile. On one hand, the background signal caused by the heat radiation increased with working temperature, and the speed with which it increased was higher than that of the real CTL intensity. This caused some peaks to almost disappear. On the other hand, the time at which the peaks appeared decreased with temperature, which caused the peaks to crowd together so that they could not be resolved. This can be explained by the Arrhenius equation. The higher temperatures accelerated the reaction. From these results, it can be concluded that, for the purpose of compound identification, temperature is an important factor and should be optimized. In the present study, 350 and 250 °C were selected as the working temperatures for the identification of medicines and organic gases, respectively. (7). Stability and Reproducibility. To determine the stability and reproducibility of this method, the luminescent response profiles of Yinqiao oral solution on nano-ZrO2 surfaces and vinyl acetate on nano-SrCO3 surfaces were examined once every 72 h for 288 h. In order to render the results clear, each luminescent response profile was parallel-shifted upward by 17%, relative to that of

its immediate predecessor. As shown in Figure 8, the luminescent response profiles are highly uniform, indicating that the method is stabile and reproducible. This may be because the sensing elements are solid catalysts and essentially nonconsumable.25 (8). Possible Mechanisms. According to the widely accepted theory of CL reactions, excited intermediates are formed during the reaction process. The emission of luminescence emission could be caused by excited intermediates falling to the ground state.36
38 In order to determine the mechanisms behind the multiple-peaked phenomenon, we detected intermediates and products of the catalytic oxidation of vinyl acetate on SrCO3 in the CRC. Meanwhile, the same experiment was carried out in the AFRC. We chose this sensing target because its luminescent response profile is relatively simple and it has a single component, which is easier to analyze than multiple components. Results showed that the multiple peak response profiles in CRC are caused by the oxidation of reactants and intermediate products over the catalyst. (See the following details.) GC/MS analysis (see the Supporting Information) shows that the CTL products of vinyl acetate in the AFRC contain plenty of vinyl acetate, acetaldehyde, acetic acid, and carbon dioxide when 8980

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Figure 9. (A) Luminescent response profile of vinyl acetate on a nano-SrCO3 surface. The reaction conditions are the same as those given in Figure 3. (B) Relationship between vinyl acetate concentration and the reaction time. (C) Concentration change curves of the products versus time. (D) Schematic diagram showing reaction pathways for vinyl acetate on a nano-SrCO3 surface.

the CTL signal returns to baseline (Figure 4B). However, only carbon dioxide was detected in the CRC when the CTL signal returned to baseline (Figure 9A). The concentrations of the products in the CRC were examined for different reaction times. As shown in Figures 9B and 9C, vinyl acetate, acetaldehyde, acetic acid, and carbon dioxide were found to coexist in the CRC at the beginning of the catalytic reaction. It can be concluded that (1) products in the CRC are the same as in the AFRC for some reaction times; (2) reactants and intermediate products cannot be fully oxidized in the AFRC, but they can be completely converted to carbon dioxide in the CRC when the reaction is run to completion. The concentration of vinyl acetate decreased gradually over time until it was completely decomposed. There was a negative linear relationship between the concentration of vinyl acetate and reaction time. The linear regression equation was found to be C =
0.2179t + 77.15 (R2 = 0.9859), where C is the residual concentration of vinyl acetate and t is reaction time. This is a zeroorder reaction. The reaction rate can be described as follows: rvinyl acetate ¼

dcvinyl acetate ¼
0:2179 dt

The rate of vinyl acetate consumption was constant over time, and the concentration of carbon dioxide increased gradually until the end of the reaction, as shown in Figure 9C. The concentration of acetic acid showed a downward trend just before the first peak in the luminescent response profile, but the concentration of acetaldehyde increased at that time. We may imagine that the first peak came from acetic acid oxidation. That is to say, acetic acid was oxidized to produce carbon dioxide molecules in the electronic excited state (CO/2 ), and then CO/2 produced photoemissions when returning to the ground state.39,40 The second peak in the luminescent response profile

appeared immediately after the acetaldehyde concentration began to decrease. In addition, no vinyl acetate or acetic acid was detected. We concluded that the second peak resulted from the direct oxidation of acetaldehyde to carbon dioxide. A schematic diagram showing the reaction pathways for vinyl acetate on nano-SrCO3 surface is shown in Figure 9D. Vinyl acetate was cracked to form acetic acid and acetaldehyde simultaneously on the SrCO3 surface, which is consistent with previous reports that vinyl acetate decomposes to acetaldehyde and acetic acid at the first step on Pd(111) and Pd(110) surfaces.41,42 During the next stage, acetic acid and acetaldehyde were oxidized to produce CO/2 , which produced photoemissions when it returned to the ground state. We detected the final reaction product of ether on both MgO and SrCO3 surfaces in the CRC. The final product of these catalytic reactions was also CO2. Based on the above, we can preliminarily explain the mechanisms of the single peak in the AFRC and multiple peaks in the CRC. When a given mass of reactants is injected into the AFRC, a fraction of those reactants is oxidized immediately upon contact with the surface of the catalyst. The rest of the reactants and the reaction products rapidly leave the surface of the catalysts, because of the driving force from the airstream. For that reason, they are not completely oxidized.18
20,38 The CTL reactions are very fast, the emission periods are relatively transitory, and CTL response profiles usually only have a single peak.17
22,43 However, in CRC systems containing enough air, reactants and reaction products cannot leave the reaction cell. Reactants can be oxidized on the catalyst to produce primary products, and then those primary products are converted to secondary products if they can be further oxidized on the catalyst. In this system, a variety of compounds that coexist within the reaction cell undergo competitive adsorption on the surface of the catalyst 8981

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Analytical Chemistry until all compounds are completely converted to carbon dioxide. In this way, the emission period of a given CTL reaction in the CRC can be longer than that in the AFRC. The total rate of any chemical reaction depends on the ratedetermining step, which can be affected by adsorption, activation energy, and diffusion coefficients.35,44 When a variety of compounds coexist in a CRC system, and the reaction rates of those on the catalyst surface are significantly different, some reactions will dominate during a certain period to form a time resolution effect. The corresponding luminescent signal can be detected. For example, in the oxidation of vinyl acetate on the nano-SrCO3 surface, theoretically, the polarity of the reaction product, acetic acid, is stronger than that of acetaldehyde, so the acetic acid is adsorbed earlier acetaldehyde, which causes the rate of acetic acid consumption to be faster than that of acetaldehyde (see Figure 8C). As the reaction period lengthens, the CTL signals of all reactions can be recorded. Integrating results over a longer period of time reveals more peaks from the luminescent response profile. Different CTL reactions show different reaction rates, reaction products, and luminescent efficiencies. That is why various analytes show characteristic luminescent response profiles, even on the same nanomaterial, and a given analyte can show unique luminescent response profiles on different nanomaterials. If the analyte has more than one component (and most solution and injections do), abundant luminescent information can be obtained.

’ CONCLUSION In summary, we have developed a new method for the rapid identification of compounds. This method involves luminescent response profiles on cataluminescence (CTL)-based sensors. Twelve types of medicines and four types of organic gases have been successfully discriminated using this new method. The catalytic oxidations of vinyl acetate on the surface of nano-SrCO3 have been studied and explain the multipeaked phenomenon in the closed reaction cell (CRC). Results show that the multipeaked luminescent response profiles in the CRC are produced when reactants and products react with the catalyst. However, the full details of these reaction mechanisms must be explored further. The proposed method offers the following distinct advantages: (1) It can recognize a wide variety of analytes directly, using only one or two sensing elements. (2) It is simple and inexpensive. (3) It is relatively environmentally friendly, because it does not require toxic reagents or solvent, and the final product is only low-concentration carbon dioxide. (4) The mode of CRC has potential applications in other types of sensors and compound-recognition schemes. ’ ASSOCIATED CONTENT

bS

Supporting Information. The figures of heating curves and luminescent response profiles of pharmic solvents. The instrument operating parameters of the GC/MS, and the GC/MS chromatograms. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*Tel.: +86 20 39366937. Fax: +86 20 39366946. E-mail: caoxiaoan [email protected].

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’ ACKNOWLEDGMENT The authors gratefully thank the National Natural Science Foundation of China (Nos. 21075024 and 41073003) and Technology Project Foundation of Guangzhou City (No. 2010Y1C021) for financial support. ’ REFERENCES (1) Counterfeit medicines; WHO Fact Sheet No. 275. Available via the Internet at http://www.who.int/medicines/services/counterfeit/ impact/ImpactF_S/en/, 2006. (2) Shank, F. R.; Carson, K. L.; Willis, C. A. J. Am. Chem. Soc. 1991, 446, 297–307. (3) Andreas, H.; Ricardo, G. O. Chem. Rev. 2008, 108, 563–613. (4) Su, M.; Li, S. Y.; Dravid, V. P. J. Am. Chem. Soc. 2003, 125, 9930– 9931. (5) Poruthoor, S. K.; Dasgupta, P. K.; Genfa, Z. Environ. Sci. Technol. 1998, 32, 1147–1152. (6) Germain, M. E.; Knapp, M. J. Am. Chem. Soc. 2008, 130, 5422– 5423. (7) Hierlemann, A.; Gutierrez-Osuna, R. Chem. Rev. 2008, 108, 563–613. (8) Albert, K. J.; Lewis, N. S.; Schauer, C. L.; Sotzing, G. A.; Stitzel, S. E.; Vaid, T. P.; Walt, D. R. Chem. Rev. 2000, 100, 2595–2626. (9) Lin, H. W.; Suslick, K. S. J. Am. Chem. Soc. 2010, 132, 15519– 15521. (10) Persaud, K.; Dodd, G. Nature 1982, 299, 352. (11) Descalzo, A. B.; Marcos, M. D.; Monte, C.; Martinez-Manez, R.; Rurack, K. J. Mater. Chem. 2007, 17, 4716–4723. (12) Stetter, J. R.; Li, J. Chem. Rev. 2008, 108, 352–366. (13) Arshak, K.; Gaidan, I. Sens. Actuators B 2006, 118, 386–392. (14) Peter, A.; Lieberzeit, A. R.; Naseer, I.; Bita, N.; Franz, L. D. Monatsh. Chem. 2009, 140, 947–952. (15) Seyama, M.; Sugimoto, I.; Nakamura, M. Biosens. Bioelectron. 2004, 20, 814–824. (16) Shi, J. J.; Zhu, Y. F.; Zhang, X. R.; Baeyens, W. R. G.; GarcíaCampa~ na, A. M. Trace-Trend. Anal. Chem. 2004, 23, 351–360. (17) Zhu, Y. F.; Shi, J. J.; Zhang, Z. Y.; Zhang, C.; Zhang, X. R. Anal. Chem. 2002, 74, 120–124. (18) Yang, P.; Ye, X. N.; Lau, C.; Li, Z. X.; Liu, X.; Lu, J. Z. Anal. Chem. 2007, 79, 1425–1432. (19) Hu, J.; Xu, K. L.; Jia, Y. Z.; Lv, Y.; Li, Y. B.; Hou, X. D. Anal. Chem. 2008, 80, 7964–7969. (20) Zhang, R. K.; Cao, X. A.; Liu, Y. H.; Peng, Y. Talanta 2010, 82, 728–732. (21) Liu, G. H.; Zhu, Y. F.; Zhang, X. R.; Xu, B. Q. Anal. Chem. 2002, 74, 6279–6284. (22) Wen, F.; Zhang, S. C.; Na, N.; Wu, Y. Y.; Zhang, X. R. Sens. Actuators B 2009, 141, 168–173. (23) Breysse, M.; Claudel, B.; Faure, L.; Guenin, M.; Williams, R. J. J.; Wolkenstein, T. J. Catal. 1976, 45, 137–144. (24) Na, N.; Zhang, S. C.; Wang, S.; Zhang, X. R. J. Am. Chem. Soc. 2006, 128, 14420–14421. (25) Wu, Y. Y.; Na, N.; Zhang, S. C.; Wang, X.; Liu, D.; Zhang, X. R. Anal. Chem. 2009, 81, 961–966. (26) Corrado, D. N.; Antonella, M.; Roberto, P.; Arnaldo, D. A. Biotechnol. Agron. Soc. Environ 2001, 5, 159–165. (27) Di Francesco, F.; Lazzerini, B.; Marcelloni, F.; Pioggia, G. Atmos. Environ. 2001, 35, 1225–1234. (28) Pavlou, A.; Turner, A. P. F.; Magan, N. Lett. Appl. Microbiol. 2002, 35, 366–369. (29) Okabayashi, T.; Toda, Matsuo, N.; Yamamoto, I.; Utsunomiya, K.; Yamashita, N.; Nakagawa, M. Sens. Actuators B 2005, 108, 515–520. (30) Stitzel, S. E.; Cowen, L.; Albert, K. J.; Walt, D. R. Anal. Chem. 2001, 73, 5266–5271. (31) Albert, K. J.; Gill, D. S.; Walt, D. R.; Pearce, T. C. Anal. Bioanal. Chem. 2002, 373, 792–802. 8982

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