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A ZnO Nanostructure-Based Quartz Crystal Microbalance Device for Biochemical Sensing Pavel Ivanoff Reyes, Zheng Zhang, Student Member, IEEE, Hanhong Chen, Ziqing Duan, Jian Zhong, Member, IEEE, Gaurav Saraf, Yicheng Lu, Olena Taratula, Elena Galoppini, and Nada N. Boustany
Abstract—We report a ZnO-nanostructure-based quartz crystal microbalance (nano-QCM) device for biosensing applications. ZnO nanotips are directly grown on the sensing area of a conventional QCM by metalorganic chemical vapor deposition (MOCVD). Scanning electron microscopy (SEM) shows that the ZnO nanotips are dense and uniformly aligned along the normal to the substrate surface. By using superhydrophilic nano-ZnO surface, more than tenfold increase in mass loading sensitivity of the nano-QCM device is achieved over the conventional QCM. The ZnO nanotip arrays on the nano-QCM are functionalized. The selective immobilization and hybridization of DNA oligonucleotide molecules are confirmed by fluorescence microscopy of the nano-QCM sensing areas. Index Terms—Biosensors, bulk acoustic waves, nanostructures, ZnO.
I. INTRODUCTION
T
HE quartz crystal microbalance (QCM) is a bulk acoustic wave device that has a high-quality (Q) factor, typically to at room temperature. It is a versatile research tool for chemistry, nanotribology, wetting transition, and superfluid transition studies. A typical QCM device consists of a piezoelectric AT-cut quartz crystal sandwiched between a pair of metal electrodes. The QCM sensors have been extensively used to monitor the change in mass loading and viscoelastic properties by measuring the shift of its resonant frequency. QCM devices can operate in the range of several MHz to tens of MHz, determined by the thickness of the quartz layer. Acoustic wave transducer technology has been applied for biosensing in recent years as sensitive, accurate, cheap, and portable sensors [1], [2]. Among them, the QCM sensors [3] in biological applications have provided certain advantages over other biosensor technologies, namely, higher sensitivity than that of the electrical and thermal biosensors [4]–[7], and more cost-effective and mobile than the optical biosensors [8]. The QCM biosensors have been used to investigate the adsorption of protein on metals [9], DNA Manuscript received November 09, 2008; revised March 18, 2009; accepted March 23, 2009. Current version published September 02, 2009. This work was supported in part by AFOSR grant (FA 9550-08-01-0452) and in part by the Rutgers Academic Excellence Fund. The associate editor coordinating the review of this paper and approving it for publication was Prof. Massood Atashbar. P. I. Reyes, Z. Zhang, H. Chen, Z. Duan, J. Zhong, G. Saraf, and Y. Lu are with the Department of Electrical and Computer Engineering, Rutgers University, Piscataway, NJ 08854 USA (e-mail:
[email protected]). O. Taratula and E. Galoppini are with the Department of Chemistry, Rutgers University, Newark, NJ 07102 USA. N. N. Boustany is with the Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854 USA. Digital Object Identifier 10.1109/JSEN.2009.2030250
immobilization [10], human serum albumin [3], and biological cell monitoring [6]. ZnO has been receiving increasing attention as a wide band gap semiconductor and as a multifunctional material. With proper doping and alloying, ZnO can be made conductive, transparent, or piezoelectric. Moreover, ZnO can be grown as thin films or as nanostructures on a variety of substrates. ZnO-based sensors possess high sensitivity to various chem, CO, icals in either gaseous or liquid states, including , , , tri-methylamine, ethanol, and , [11], [12]. Highly sensitive gas sensors have been demonstrated combining surface acoustic wave devices (SAW) with ZnO nanostructures to enhance the gas sensing performance [13]–[15]. are known to be ZnO and its ternary alloy, biocompatible oxides, in which Zn and Mg are important elements for neuroetransmitter production and enzyme function [13]. Furthermore, ZnO nanorods have been shown to be compatible with intracellular material [16] and highly sensitive to pH changes inside cellular environments [17], as well as detection of enzymatic reactions with target biochemicals [18]. The biocompatibility of ZnO and its potential for biosensing applications are further demonstrated in [19] and [20], where antibody immunosensing is achieved through surface functionalization of ZnO-based SAW devices. In this paper, we report a nano-QCM biosensor by growing ZnO nanotip arrays directly on the sensing area of a conventional QCM. We developed a biochemical functionalization scheme for the ZnO nanotips to facilitate selective immobilization and hybridization of DNA oligonucleotides. Enhanced sensitivity is achieved through wettability control of the nanotip sensing area. Liquid sample intake of the device is greatly reduced due to the very large effective surface area provided by the nanotips. The resulting biomolecule reactions with the functionalized nanotips are demonstrated from the mass loading on the nano-QCM and confirmed through fluorescence microscopy. The experimental results show promising potential for the nano-QCM as a low cost, sensitive, and compact biosensor. II. DEVICE STRUCTURE The nano-QCM device consists of ZnO nanotip arrays that are integrated with a standard AT-cut QCM by growing them directly on the sensing area of the QCM using MOCVD. The nano-QCM device schematic is shown in Fig. 1(a) and its multilayer structure in Fig. 1(b). The piezoelectric AT-cut quartz sandwiched between two layer has a thickness of 166.8 100 nm gold electrodes. The quartz substrates have a diameter
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Fig. 1. Schematic diagram of the nano-QCM device. (b) Cross section of the multilayer structure of the nano-QCM.
Fig. 3. Simulated device impedance spectrum of the nano-QCM showing a frequency shift of 3.1414 kHz corresponding to a mass loading of 5 L of water.
Fig. 2. FESEM image of ZnO nanotips grown by MOCVD. The ZnO nanotips have an average height of 700 nm and average diameter of 70 nm.
of 1.37 cm and the sensing area is 0.2047 . Single crystalline ZnO nanotips of 700 nm height and 70 nm in diameter, spacing are directly grown on the sensing area with through a shadow mask with a diameter of 0.51 cm. ZnO nanotips were grown by MOCVD using Diethylzinc (DEZn) and as Zn source and oxidizer, respectively. The substrate temand chamber pressure remained at perature was kept at around 50 Torr during the growth. The field emission scanning electron microscope (FESEM) image for the vertically aligned ZnO nanotips is shown in Fig. 2. III. DEVICE TESTING A. Device Calibration The characterization and testing of the nano-QCM device was conducted using an HP 8573D Network Analyzer (Agilent Technologies, Palo Alto, CA). The forward transmission paramof the device was measured. The mass loading on the eter QCM can be determined directly from the shift in its resonant frequency and its mass sensitivity, is given by the formula
(1) where is the resonant frequency shift due to mass loading, is the resonant frequency of the QCM, is the mass loading, and is the area of the quartz layer.
The measured resonant frequency of the standard QCM is 9.9936 MHz, while the nano-QCM has 9.9163 MHz resonance. Sauerbrey’s model [21] is popular to calculate the QCM’s mass loading. However, Sauerbrey’s model which is typically used for dry sample testing is not accurate to predict frequency shifts in the liquid phase. In the liquid case, the acoustic waves would leak out to the liquid layer and introduce a damping effect on the resonating acoustic modes, resulting in reducamplitude tion in the forward transmission parameter and change in its phase, which collectively cause the shift in resonant frequency. For simulation of QCM’s mass loading in liquid case, we have used our multilayer transmission line (MTL) model [22] in which we consider the acoustic wave propagation through the different layers of the QCM device and calculate the acoustic impedance of the device by treating each layer as a two-port system. The MTL simulation parameters of the nano-QCM follow the multilayer structure shown in Fig. 1(b). The density of the piezoelectric AT-cut quartz layer , and its acoustic used in the simulation is 2.648 . For the Au electrodes the density velocity is 3.336 and acoustic velocity is 3.240 . is 19.32 Similarly, for the ZnO sensing layer we used the density value and acoustic velocity of 6.152 . of 5.665 The output of the MTL simulation is the device impedance spectrum and is shown in Fig. 3. The simulated frequency shift of water on the nano-QCM is due to mass loading of 5 3.1414 kHz, which is in good agreement with the experimental data of 2.9034 kHz shown in Fig. 4. B. Sensitivity Enhancement Through Wettability Control We have shown that ZnO nanotips can be made reversibly superhydrophylic and superhydrophobic by UV irradiation and oxygen annealing, respectively [23]. Making the nanosensing area superhydrophilic significantly decreases the liquid sample consumption. In this work, the nano-QCM is exposed under UV radiation from a lamp (Model 66002, Oriel Optics, Stratford CT) for 10 min to make the nanosensing area superhydrophilic. The nano-QCM with the superhydrophilic nano-ZnO surface of DI water to cover the entire sensing only requires 0.5 for the standard QCM. Morearea, while it needs to take 16 over, the same nano-QCM device exhibits a tenfold increase in
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Fig. 4. S parameter measurement of the nano-QCM showing a frequency shift of 2.9034 kHz corresponding to a mass loading of 5 L of water.
Fig. 5. Simplified schematic of the chemical functionalization scheme for the ZnO nanotips to implement selective DNA immobilization and hybridization.
frequency shift in detecting the same 1 mL of water from the standard QCM (6.2 kHz for the nano-QCM and 0.7 kHz for the standard QCM). This enhancement in device sensitivity is attributed to the giant effective sensing area for the liquid sample introduced by the superhydrophilic ZnO nanotip surface. IV. FUNCTIONALIZATION OF ZNO NANOTIPS An optimized chemical functionalization scheme was developed for the ZnO nanotips. The functionalization scheme is used to implement the selective binding of specific DNA oligonucleotides on the ZnO nanotips, and then hybridized with its fluorescent-tagged complement. The detailed chemical binding procedures for each functionalization step will be published elsewhere [24]. A set of optimized linkers to functionalize ZnO with DNA in this work can be summarized in three steps (as shown in Fig. 5): step 1: ZnO linker; step 2: DNA immobilization; and step 3: fluorescence-tagged DNA hybridization. The bifunctional linker hexadecanoic carboxylic acid N-(15-carboxypentadecanoyloxy)succinimide (NHSHA) was used with the COOH group to form a N-hydroxysuccinimide-ester functionalized surface on ZnO nanotips. The nano-QCM sensing area was immersed in the linker solution in a Teflon liquid flow static cell (International Crystal Manufacturing Company, Inc.) for 12 h (step 1). DNA incubation
Fig. 6. Demonstration of selective DNA from the fluorescence images (bar is 100 ) of the ZnO nanotips grown on C-sapphire with (a) step 1 only, (b) step 1 step 2 (c) step 1 step 3, and (d) step 1 step 2 step 3. Only the nanotips with properly immobilized and hybridized DNA molecules are positively fluorescing.
+
m
+
+
+
was done on the device for 4 h (step 2) and hybridization took 1.5 h (step 3). After every step, the nanotips were rinsed with a pH-controlled buffer solution and gently dried under gentle nitrogen flow. It is found that the selective DNA immobilization and hybridization can only be achieved on the ZnO nanotips if the three steps are completely followed in order. In this work, we also performed fluorescence imaging of the ZnO nanotips simultaneously grown on c-sapphire substrate to confirm if selective immobilization and hybridization was achieved or not when different combinations of the chemical steps were implemented. An Axiovert 200M confocal fluorescence microscope (Zeiss Axiovert 200M, Gottingen, Germany) was used with a 510 nm filter and 480 nm excitation to obtain reflection type fluorescence images of the ZnO nanotips. Fig. 6(a)–(d) show fluorescence images of the nanotips for different combinations of the three chemical steps: in (a) only step 1 is performed, in (b) only steps 1 and 2 are performed, in (d) only steps 1 and 3 are performed, and in (d) all three steps are performed in order. Only the nanotips with all the three complete steps are positively fluorescing which confirms the selective binding of the ZnO nanotips. V. DNA IMMOBILIZATION AND HYBRIDIZATION USING THE NANO-QCM DEVICE The nano-QCM device is used to sense the mass loading of each chemical step outlined earlier. The device sensing area was first made superhydrophilic by exposing it to UV light for 10 minutes. The device is then calibrated for DNA molecule detection by adding 2 of nonactivated DNA oligonucleotide, which yielded a frequency shift of 0.3 kHz due to mass loading. The device sensitivity of 154.817 was calculated using (1). We then performed the optimized three-step procedure on the nano-QCM for DNA immobilization and hybridization that was outlined in the previous section. The frequency shifts of the nano-QCM’s parameter, resulted from the mass loading effect for each of the three chemical binding steps. The frequency response demonstrating the mass loading detection of each chemical step is shown in Fig. 7. The shift of 1.992 kHz after step 1 confirms that there are 265.606 ng of the linker molecules on the nano-QCM sensing area. A shift of 2.271 kHz after step
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REYES et al.: A ZNO NANOSTRUCTURE-BASED QUARTZ CRYSTAL MICROBALANCE DEVICE FOR BIOCHEMICAL SENSING
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is promising to be used for enhanced chemical reaction analysis and high precision mass determination. Furthermore, the possibility of operating the nano-QCM wirelessly enables it to be used in noninvasive sensing in controlled biological testing environments. VI. CONCLUSION
Fig. 7. Frequency response (S ) of the nano-QCM, (Step 0) nano-QCM only, (Step 1) linker coating on ZnO, (Step 2) DNA immobilization, and (Step 3) DNA hybridization.
Fig. 8. (a) Fluorescence image (bar is 50 m) of the nano-QCM device sensing area (center region) after DNA hybridization and (b) fluorescence image (bar is 100 m) of the edge of the sensing area revealing binding only at the nanotip sites.
2 shows that 302.673 ng of DNA molecules are immobilized on the nanotips via the bifunctional linkers, and finally, a shift of 2.271 kHz after step 3 shows that 264.939 ng of the fluorescence-tagged complement DNA molecules are hybridized on the nanotips containing immobilized DNA. The uniform shift frequency throughout the three-step chemical process in indicates that the immobilized and hybridized DNA molecules have uniformly attached to the sensing area. The sensing area of the nano-QCM was washed with a pH-controlled buffer after hybridization and fluorescence imaging confirms that the immobilization and hybridization only occurs at the nanotip sites. Fig. 8(a) shows the fluorescence image of the nano-QCM sensing area after the three-step process which confirms the presence of hybridized DNA on the nanotips. Fig. 8(b) shows the fluorescence image of the edge of the sensing area of the same device confirming that the DNA molecules bind only to the ZnO nanotip-covered sensing area of the device. The three-step DNA binding scheme was also performed on a standard QCM. The experiment yielded no discernible freparameter and showed negatively quency shift from the fluorescing images of the sensing area. This confirms that the linker layer is validated only to ZnO nanotips and DNA. The ability of the ZnO nanotips to enhance the sensing function of the conventional QCM to facilitate and detect selective DNA immobilization and hybridization make the nano-QCM a promising biocompatible sensing device. Such a sensor also possesses advantages, including high sensitivity, simple structure, low cost, and compact size. The nano-QCM biosensor
In summary, a novel ZnO nanostructure-based QCM device (nano-QCM) was demonstrated for use in selective biochemical sensing. A layer of ZnO nanotips was grown directly on the sensing layer via MOCVD. Integration of ZnO nanotips on the standard QCM greatly enhances the performance of the device. The superhydrophobic ZnO nanotip layer increases the device’s mass loading frequency shift tenfold as compared to a standard QCM; furthermore, it also significantly reduces the liquid sample consumption of the device. The results from device simulations using the transmission line model of multilayer bulk acoustic wave structures show good agreement with the experimental data. Fluorescence-tagged DNA molecules on the functionalized nanotips show selective binding to only linker-activated DNA. The nano-QCM device selectively detects DNA immobilization and hybridization using two types of optimized nanotip functionalization schemes. REFERENCES [1] H. Wohltjen, D. Ballantine, R. White, S. Martin, A. Ricco, E. Zellers, and G. Frye, Acoustic Wave Sensors-Theory, Design, and Physico-Chemical Applications. New York: Academic, 1997. [2] R. M. Lec and P. A. Lewin, “Acoustic wave biosensors,” in Proc. 20th Annu. IEEE Eng. Med. Biol. Soc., 1998, vol. 20, pp. 2785–2785. [3] M. Muratsugu, F. Ohta, Y. Miya, T. Hosokawa, S. Kurosawa, N. Kamo, and H. Ikeda, “Quartz crystal microbalance for the detection of microgram quantities of human serum albumin: Relationship between the frequency change and the mass of protein adsorbed,” Anal. Chem., vol. 65, pp. 2933–2933, 1993. [4] A. Q. Contractor, T. N. Sureshkumar, R. Narayanan, S. Sukeerthi, R. Lal, and R. S. Srinivasa, “Conducting polymer-based biosensors,” Electrochimica Acta, vol. 39, pp. 1321–1321, 1994. [5] L. Ghindilis, P. Atanasov, M. Willkins, and E. Willkins, “Immunosensors: Electrochemical sensing and other engineering approaches,” Biosens. Bioelectron., vol. 13, pp. 113–113, 1998. [6] A. Alessandrini, M. A. Croce, R. Tiozzo, and P. Facci, “Monitoring cell-cycle-related viscoelasticity by a quartz crystal microbalance,” Appl. Phys. Lett., vol. 88, Feb. 2006. [7] K. -H. Choi, J. -M. Friedt, F. Fredereix, A. Campitelli, and G. G. Borghs, “Simultaneous atomic force microscope and quartz crystal microbalance measurements: Investigation of human plasma fibrinogen adsorption,” Appl. Phys. Lett., vol. 81, no. 7, pp. 1335–1335, 2002. [8] A. Neef, R. Schafer, C. Beimfohr, and P. Kampfer, “Fluorescence based rRNA sensor systems for detection of whole cells of Saccharomonospora SPP and Thermoactinomyces SPP,” Biosens. Bioelectron., vol. 18, pp. 565–565, 2003. [9] J. Homola, S. S. Yee, and G. Gauglitz, “Surface plasmon resonance sensors: Review,” Sens. Actuators B, vol. 54, pp. 3–3, 1999. [10] X. C. Zhou, L. Q. Huang, and S. F. Y. Li, “Microgravimetric DNA sensor based on quartz crystal microbalance: Comparison of oligonucleotide immobilization methods and the application in genetic diagnosis,” Biosens. Bioelectron., vol. 16, pp. 85–85, 2001. [11] V. I. Anisimkin, M. Penza, A. Valentini, F. Quaranta, and L. Vasanelli, “Detection of combustible gases by means of a ZnO-on-Si surface acoustic wave (SAW) delay line,” Sens. Actuators B, vol. 23, pp. 197–197, 1995. [12] T.-J. Hsueh, S.-J. Chang, C.-L. Hsu, Y.-R. Lin, and I.-C. Chen, “Highly sensitive ZnO nanowire ethanol sensor with Pd adsorption,” Appl. Phys. Lett., vol. 91, Jul. 2007.
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[13] A. Z. Sadek, W. Wlodarski, Y. X. Li, W. Yu, X. Li, X. Yu, and K. Kalantar-zadeh, “A ZnO nanorod based layered ZnO/64 degrees YX LiNbO SAW hydrogen gas sensor,” Thin Solid Films, vol. 515, no. 24, pp. 8705–8708, Oct. 2007. [14] S. J. Ippolito, S. Kandasamy, K. Kalantar-Zadeh, W. Wlodarski, K. Galatsis, G. Kiriakidis, N. Katsarakis, and M. Suchea, “Highly sensitive layered ZnO=LiNbO SAW device with InO selective layer for NO and H gas sensing,” Sens. Actuators B, vol. 111, pp. 207–212, Nov. 2005. [15] F. C. Huang, Y. Y. Chen, and T. T. Wu, “A room temperature surface acoustic wave hydrogen sensor with Pt coated ZnO nanorods,” Nanotechnology, vol. 20, no. 6, Feb. 2009. [16] B. G. Miler and T. W. Trantim, “A role for Zinc in OMP decarboxylase, an unusually proficient enzyme,” J. Amer. Chem. Soc., vol. 120, pp. 2666–2666, 1998. [17] S. M. Al-Hilli, R. T. Al-Mofarji, and M. Willander, “Zinc oxide nanorod for intracellular pH sensing,” Appl. Phys. Lett., vol. 89, p. 173119, Oct. 2006. [18] A. Wei, X. W. Sun, J. X. Wang, Y. Lei, X. P. Cai, C. M. Li, Z. L. Dong, and W. Huang, “Enzymatic glucose biosensor based on ZnO nanorod array grown by hydrothermal decomposition,” Appl. Phys. Lett., vol. 89, p. 123902, Sep. 2006. [19] S. Krishnamoorthya, A. A. Iliadis, T. Beic, and G. P. Chrousos, “An interleukin-6 ZnO=SiO =Si surface acoustic wave biosensor,” Biosens. Bioelectron., vol. 24, no. 2, pp. 313–318, 2008. [20] K. Kalantar-Zadeh, W. Wlodarskia, Y. Y. Chenc, B. N. Fryc, and K. Galatsisa, “Novel love mode surface acoustic wave based immunosensors,” Sens. Actuators B, vol. 91, no. 1–3, pp. 143–147, 2003. [21] G. Sauerbrey, “Verwendung Von Schwingquarzen Zur Wagung Dunner Schichten und Zur Mikrowagung,” Z. Phys, vol. 155, pp. 206–206, 1959. [22] Y. Chen, G. Saraf, R. H. Wittstruck, N. W. Emanetoglu, and Y. Lu, in Proc. 2005 IEEE Int. Frequency Control Symp., 2005, pp. 142–142. [23] Z. Zhang, H. Chen, J. Zhong, G. Saraf, and Y. Lu, TMS & IEEE J. Electron. Materials, vol. 36, no. 8, pp. 895–895, 2007. [24] O. Taratula, R. Mendelsohn, E. Galoppini, P. I. Reyes, Z. Zhang, Y. Chen, G. Saraf, and Y. Lu, “Stepwise functionalization of ZnO nanostructures with DNA for biosensing applications,” Langmuir, Jun. 2009, to be published.
Pavel Ivanoff Reyes was born in Cavite City, Philippines. He received the B.S. degree in applied physics from the National Institute of Physics, University of the Philippines, Diliman, in 1996 and the M.S. degree in electrical engineering from the University of the Philippines, Diliman, in 1999. He is currently working towards the Ph.D. degree at Rutgers University, New Brunswick, NJ, under Dr. Y. Lu on research on multifunctional ZnO nanostructure-based biosensors. He was formerly with the University of Philippines, where he subsequently joined the faculty as an Assistant Professor of Electrical Engineering initiating graduate courses and research in optical devices. He joined the Optical Fiber Research of Bell Laboratories, Murray Hill, NJ, in 2000 (which later became OFS Fitel). His work at Bell Labs included fiber grating-based optical devices. In 2005, he joined the Department of Electrical and Computer Engineering, Rutgers University.
Zheng Zhang (S’03) was born in Hangzhou, China, in 1979. She received the B.S. degree in information science and electronic engineering from Zhejiang University, Hangzhou, China, in 2001, the M.S. degree in electrical and computer engineering and the Ph.D. degree from Rutgers University, New Brunswick, NJ, in 2004 and 2007, respectively, where she worked with Dr. Y. Lu on ZnO-based SAW devices and nanostructured devices for sensors. She is currently a Research Engineer at Spansion, CA.
Hanhong Chen received the B.S. degree in materials science and engineering, specializing in electronic ceramics from Zhejiang University, Hangzhou, China, in 1999, the M.S. degree from the State Key Laboratory of Silicon Materials, Zhejiang University, in 2002, and the Ph.D. degree from the Department of Electrical and Computer Engineering, Rutgers University, New Brunswick, NJ, under Dr. Y. Lu in 2007. His research interests include materials MOCVD growth and characterization of ZnO-based epitaxial films and nanotips. He is currently an Engineer at Intermolecular, CA.
Ziqing Duan received the B.E. degree in materials science and engineering from Zhengzhou University, Zhengzhou, China, in 2002 and the M.E. degree in materials science and engineering from the Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, in 2005. He is currently working towards the Ph.D. degree at the Department of Electrical and Computer Engineering, Rutgers University, New Brunswick, NJ. His research interests include MOCVD growth and characterization of ZnO-based thin films and nanostructures. He is also interested in the ZnO-based photovoltaic devices.
Jian Zhong (S’00–M’07) received the B.S. and M.S. degrees in electronic engineering from Tsinghua University, Beijing, China, and the Ph.D. degree in electrical and computer engineering from Rutgers University, New Brunswick, NJ. She is currently a Research Associate of Electrical and Computer Engineering at Rutgers University. Her research interests include ZnO-based optical and electrical devices and sensors.
Gaurav Saraf received the B.Tech. degree in metallurgical and materials engineering from the Indian Institute of Technology, Kharagpur, in 2001, the M.S. degree in ceramics and materials engineering from Rutgers University, New Brunswick, NJ, in 2003, and the Ph.D. degree in electrical engineering in 2008 working under Prof. Y. Lu at the Department of Electrical and Computer Engineering, Rutgers University. His research interests include MOCVD growth of ZnO and Mg Zn O thin films and heterostructures, growth, and fabrication of ZnO-based nanoscale structures. His interests also include detailed structural characterization and understanding of the growth mechanism. He is currently a Staff Scientist at Energy Photovotaic (EPV) Inc., NJ.
Yicheng Lu received the B.S. degree in applied physics from Jiao Tong University, Shanghai, China, in 1982 and the Ph.D. degree in electrical engineering from the University of Colorado, Boulder, in 1988. In 1988, he joined the faculty of Rutgers University, New Brunswick, NJ, where he is currently the Paul S. and Mary W. Monroe Faculty Scholar Professor and Chairman of the Department of Electrical and Computer Engineering, and a graduate faculty member in the Department of Ceramics and Materials Engineering. His early research involved metal semiconductor contacts and rapid thermal processing for electronic materials. Since he joined Rutgers University, his research includes vacuum microelectronics, piezoelectric thin
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REYES et al.: A ZNO NANOSTRUCTURE-BASED QUARTZ CRYSTAL MICROBALANCE DEVICE FOR BIOCHEMICAL SENSING
films and devices, wide bandgap semiconductors (ZnO and GaN), and integrated radio frequency (RF) passive devices. His recent research has been focused on ZnO-based materials, nanostructures, and multifunctional devices. He has published more than 200 refereed articles and received 16 U.S. patents. Prof. Lu received the 1993 Warren I. Susman Award for Excellence in Teaching, which is the highest teaching award at Rutgers University. In 1994, he received the Board of Trustees Research Fellowship Award for Scholarly Excellence from Rutgers University. In 2002, he received the Rutgers University Scholar-Teaching Award and the IEEE Outstanding Student Counselor and Advisor Award in 1995.
Olena Taratula received the M.S. degree in chemistry from the Ivan Franko National University of Lviv, Lviv, Ukraine, in 2002 and the Ph.D. degree in chemistry from Rutgers, The State University of New Jersey, New Brunswick, NJ, in 2008. Currently, she is a Postdoctoral Fellow at University of Pennsylvania, Chemistry Department. In addition to her interest in functionalization of metal-oxide semiconductor surfaces with organic and inorganic dyes for dye sensitized solar cells (DSSCs) and with biomolecules for biosensor applications, her research is focused on the development of multimodal probes based on xenon-gas encapsulated inside of cryptophane cages modified with the recognition moiety for Xe SPECT and Xe MRI. molecular imaging of cancer by
Elena Galoppini was born in Pisa, Italy. She received the Laurea degree in chimica from the Università di Pisa, and the Ph.D. degree from the University of Chicago, Chicago, IL, in 1994, working on the synthesis of cage molecules that are derivatives of cubane (C H , a strained hydrocarbon). After a two-year Postdoctoral Fellowship at the University of Texas at Austin, she joined Rutgers University, Newark, NJ, where she is now a Professor of Chemistry. In 2006, she was a Visiting Professor
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at the Center for Molecular Devices, Royal Institute of Technology, Stockholm, Sweden, to conduct research on electron transport in ZnO nanotips solar cells. She has published over 50 research papers and presented at numerous meetings and symposia, in the U.S., Europe, and Asia. She is a Kavli Frontiers of Sciences Fellow. Her synthetic group develops dye-linker-anchor molecules that bind to semiconductor nanoparticles to study electronic processes at the interface. Such model compounds find application for understanding the mechanisms of solar cells, and to develop new electrochromic materials. Her research interests involve a combination of synthesis and spectroscopy. More recently, the surface functionalization methodologies developed by her group have found application for the development of nanostructured ZnO-integrated sensors designed by Prof. Y. Lu and coworkers. Prof. Galoppini is a recipient of the Alan Berman Research Publications Award, and the recipient of a Distinguished Service Award from the New York Italian Consulate.
Nada N. Boustany received the Ph.D. degree in medical physics from the Harvard-MIT Division of Health Science and Technology, Cambridge, MA, in 1997. She joined Johns Hopkins University as a Distinguished Postdoctoral Fellow in 1998 and as a Research Associate in 2001. In 2003, she moved to Rutgers University, New Brunswick, NJ, where she is an Assistant Professor of Biomedical Engineering. Her research is focused on utilizing light to study cellular function. Exploring the limits of optical spectroscopy and novel possibilities in cancer diagnosis was the focus of her doctoral work. There she showed how ultraviolet resonance Raman scattering could be used for bioassay and histochemistry. Since then, she has been investigating the relationship between specific gene expression and subcellular structure and dynamics during cell death. As part of this research, she has developed an imaging method that significantly extends the sensitivity of light microscopy to subtle changes in subcellular morphology.
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