Letter pubs.acs.org/acssensors
Periodically Patterned Au-TiO2 Heterostructures for Photoelectrochemical Sensor Limin Guo,† Zhao Li,‡ Kyle Marcus,‡ Steven Navarro,† Kun Liang,† Le Zhou,‡ Prabhu Doss Mani,‡ Stephen J. Florczyk,‡ Kevin R. Coffey,‡ Nina Orlovskaya,§ Yong-Ho Sohn,‡ and Yang Yang*,†,‡ †
NanoScience Technology Center, ‡Department of Materials Science and Engineering, and §Department of Mechanical and Aerospace Engineering, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816, United States S Supporting Information *
ABSTRACT: Periodically patterned Au nanorods in TiO2 nanocavities (Au NRs@TiO2) were fabricated via magnetron sputtering followed by a thermal dewetting process. This innovative Au NRs@TiO2 heterostructure was used as a plasmonic sensing platform for photoelectrochemical detection of glucose and lactose. This Au NRs@TiO2 patterned heterostructure possesses superior sensing properties to other Au nanoparticle-based sensors because (i) localized surface plasmon resonance (LSPR) generated at Au/TiO2 interfaces enhanced sensitivity of glucose (lactose) amperometric detection; (ii) periodic Au nanocrystals in TiO2 nanocavities accelerated charge separation and transfer rate, especially under monochromatic blue light irradiation; (iii) discrete planar architectures comprising Au NRs immobilized on TiO2 substrates significantly improved stability and reusability of the sensors. A low detection limit of 1 μM (10 μM) and a high sensitivity of 812 μA mM−1 cm−2 (270 μA mM−1 cm−2) were achieved on the Au NRs@TiO2 heterostructures for glucose (lactose) detection without the addition of enzymes. Good selectivity and superb stability over more than 8 weeks was also demonstrated using these Au NRs@TiO2 heterostructures for glucose (lactose) detection. Additionally, this cost-efficient technique can be easily extended to other photoelectrochemical sensing systems when considering the combination of sensing and visible or infrared light source enhancement. KEYWORDS: plasmonics, photoelectrochemistry, heterostructure, nanopatterns, sensors
L
mellitus.7,8 Conditions such as lactose intolerance can cause several symptoms including abdominal distention, pain, and diarrhea.9,10 Monitoring glucose and lactose levels in blood or other fluids can aid in disease management and assist in preventing associated medical risks.11 However, conventionally used enzyme-based glucose and lactose biosensors suffer from poor stability due to enzyme consumption and fermentation during long-term utilization.12,13 Therefore, enzyme-free biosensors have become an attractive alternative. Spectrometric assays including luminescence and fluorescent labeling have been widely employed for biosensing techniques. Unfortunately, spectrometric assays suffer from moderate accuracy and selectivity which limit their application at lower inspection concentrations in blood or fluids of patients.1,2 Photoelectrochemical biosensing has therefore been explored as an efficient and facile way to sense glucose and lactose due to their high sensitivity, reasonable selectivity, low cost, and low detection limit.14 Nanostructured materials are considered to be far superior to bulk materials for biosensing due to their high reactive surface
ocalized surface plasmon resonance (LSPR) has been studied intensively among noble metals (Au, Ag, Pt, etc.) and noble metal alloys (Au−Cu, Au−Pb, etc.) for their potential application as sensors.1,2 LSPR assisted spectrometric detection processes are generally found in the literature. However, relatively few have reported using LSPR in amperometric techniques, which may open new possibilities for sensitivity enhancement and fulfill portable biosensing requirements by offering low fluid level detection and real-time feedback.3−5 The LSPR extinction band mainly originates from the oscillation of “hot” electrons within the vicinity of noble metal particles. Furthermore, the resonant peak wavelength, photoabsorption magnitude, and decay length of LSPR fields significantly depend upon noble metal particle size, shape, interspace, and environmental composition.6 Consequently, studying the effect of nanostructures on LSPR properties, optimizing material design, and improving photoelectrochemical sensitivity/detection limits are important factors to consider for LSPR biosensor research. Sugar derivatives, such as D-glucose and D-lactose, are essential components of the human body and are commonly found in a variety of food sources. However, over consumption of these sugars is a risk factor for many chronic diseases like hyperinsulinemia, elevated blood pressure, and diabetes © XXXX American Chemical Society
Received: April 17, 2017 Accepted: May 16, 2017 Published: May 16, 2017 A
DOI: 10.1021/acssensors.7b00251 ACS Sens. XXXX, XXX, XXX−XXX
Letter
ACS Sensors area, unique physical, and chemical properties.11,15 However, without proper dispersion and immobilization, powdered nanomaterials suffer from particle aggregation and performance degradation resulting in major barriers concerning stability and reusability of sensors.6,16 To address the sensitivity, stability, and recyclability issues observed with nanoparticle-based sensors, we demonstrate an innovative strategy of using patterned Au-TiO2 heterostructure for plasmonic photoelectrochemical detection of common sugars such as glucose and lactose. Here, more specifically, periodically patterned Au nanorods (NRs) and nanoporous (NPs) layers immobilized on TiO2 nanocavities (Au NRs@TiO2 and Au NPs@TiO2, respectively) were rationally developed. Unlike traditional air or aqueous dielectric property-based LSPR sensing, the enhanced plasmonic charge separation of Au particles is utilized here for photocurrent signaling. These highly ordered nanopatterns enable high sensitivity, good stability, and reusability for biosensing due to rapid detection of biomolecules over a planar thin-film with high surface area. A greatly enhanced sensitivity and selectivity of photoelectrochemical detection of sugars under solar light and monochromatic blue light irradiation is demonstrated. The Au nanostructure dependent plasmonic resonance and biosensing mechanism are discussed further. A typical fabrication route for periodically patterned Au NRs@TiO2 plasmonic films is schematically illustrated in Figure 1a. Anodic treatment of Ti foil was employed to create
where reactions can occur more readily. These anodized TiO2 thin-films were rationally designed to reduce charge transfer resistance for catalytic reactions and enhance sensitivity for biomolecule detection. A 10-nm-thick layer of Au was deposited on the surface of TiO2 nanocavities by magnetron sputtering. After Au layer deposition, the diameter of the honeycomb-shaped pores of TiO2 nanocavities decreased slightly (Figure S1b), indicating a conformal Au coating was achieved. Before thermal dewetting treatments of the Au@TiO2 films at 500 °C in N2 flow for 2 h, samples were pretreated by pressing at room temperature and 80 °C, respectively, to improve affinity between the Au coating and TiO2 film. Pressing pretreatment is a crucial step in forming periodically patterned Au@TiO2 heterostructures because it was found that randomly dispersed and irregularly large Au particles were found on the TiO2 films without pressing treatment (Figure S1c). Due to the pinning effect of TiO2 nanocavities on the deposited Au layer, a nanoporous layer of Au (Au NPs@TiO2, diameter: 40 nm) was formed after room temperature pressing followed by thermal dewetting (Figure 1b). The formation of a continuous Au nanoporous layer indicates that Au agglomeration likely takes place on the side-walls of TiO2 nanocavities during thermal dewetting. The pinning effect of TiO 2 nanocavities can be released by pressing treatment at 80 °C. Periodically patterned Au NRs were then obtained after thermal dewetting, implying that the continuous Au layer was divided into discontinuous patches owing to pinning effect release after pressing at 80 °C. These small patches formed detached islands inside TiO2 nanocavities after pressing and further agglomerated to form discrete Au NRs (Figure 1c, Au NRs@TiO2) after thermal dewetting treatment. These discrete Au NRs, with a diameter of 50 nm, individually half-filled the TiO2 nanocavities with a periodic interval of 20 nm (Figure S1d,e, inset in Figure 1c). Lattice fringe of the Au NRs identified from the HR-TEM image (Figure 1d) was estimated to be 0.23 nm, which denotes (111) face of cubic Au. These Au NRs@TiO2 films were rationally designed for solar and monochromatic light-assisted photoelectrochemical sensing due to the LSPR system generated by Au NPs or isolated Au NRs in dielectric medium (TiO2). XRD peaks of TiO2, Au NPs@TiO2, and Au NRs@TiO2 films (Figure S 1f) agree well with rutile TiO2 (PDF Card No.: 73-1765) and cubic Au (PDF Card No.: 4-787). The Au NRs@ TiO2 film shows a stronger diffraction peak intensity at 38.2° (the (111) face of cubic Au) than the Au NPs@TiO2 film, indicating Au NRs have better crystallinity than the Au NPs. UV−vis absorption spectra of the thin-films (Figure 2a) show considerably enhanced visible-light absorption for the TiO2 films decorated with Au nanostructures (NPs and NRs). A stronger LSPR is observed on the Au NRs@TiO2 (detailed study on photoresponse mechanism is shown in the Supporting Information).14,17−19 Near-field distributions for Au NRs@TiO2 and Au NPs@ TiO2 were simulated by FEM as shown in Figure 2c,d.20 Strong electrical field enhancement on the Au NRs@TiO2 film surface is determined by light resonance coupling to the local surface plasmon at 500 nm laser (Figure 2c). A weaker electric field enhancement is observed for the Au NPs@TiO2 film because of the nonisolated Au construction and lower dielectric constant of the air medium (Figure 2d). For an individual Au NR, electric field antinode covers a distance longer than half of the inter-rod space (>20 nm), indicating a zero-gap field distribution along the x axis of Au NRs@TiO2 film and
Figure 1. (a) Schematic illustration of the fabrication route for the Au NRs@TiO2 heterostructure: Step 1, anodic formation of TiO2 nanocavities; Step 2, 10 nm Au layer deposition; Step 3, thermal dewetting treatment. (b,c) Top view SEM images of Au NPs@TiO2 and Au NRs@TiO2, respectively. (d) TEM image of the isolated Au NRs. The scale bars in b−d indicate 200, 500, and 5 nm, respectively.
highly ordered TiO2 nanocavities with a pore diameter of 70 nm and film thickness of less than 100 nm (Figure S1a). The resulting honeycomb-shaped pores form interconnected patterns with a greatly increased high surface area. This is an important concept to consider because exploiting the high surface area allows for a significant increase in possible locations B
DOI: 10.1021/acssensors.7b00251 ACS Sens. XXXX, XXX, XXX−XXX
Letter
ACS Sensors
which exposes more Au sites for the indirect oxidation of glucose, leading to an oxidation current peak at 0.4 V.23,24 One control experiment shows that the bare TiO2 film has no activity toward glucose oxidation. Another control experiment indicates that Pt foil delivers very weak glucose oxidation peaks and minimal photoresponse changes (Figure S2b,c). Photoelectrochemical glucose detection was further performed under simulated solar light irradiation (Figure S2c). A significant solar response and enhanced glucose oxidation current were achieved in the Au NRs@TiO2 film due to the strong LSPR (compared in Figure S2b,c). The Fermi level of LSPR induced electrons is higher than the TiO2 substrate conduction band, which facilitates plasmonic “hot” electron transfer to the TiO2 electrode and leaves “holes” on the Au surface. The free “holes” help absorption of OH− in PBS solution and provide more AuOH active sites, which is critical for glucose oxidation.24 Consequently, a photocurrent increment is found accordingly (Figure S3a) and a schematic diagram of the process is shown in Figure S3b. CV curves of the Au NRs@TiO2 film were also recorded at different scan rates from 5 to 300 mV s−1 in 5 mM glucose solution (Figure S3a). Current densities and potentials of glucose oxidation increases proportionally to the scan rates, demonstrating diffusion-controlled, irreversible processes involved in the reactions. A slight influence of scan rate on indirect glucose oxidation is observed, which is mainly attributed to the AuOH formation rate.2 Sensitivity of glucose oxidation using the Au NRs@TiO2 film was first characterized by performing CV in PBS solutions with different glucose concentrations (0−10 mM) in the dark (Figure S4a), simulated solar light (Figure S4b), and blue light (Figure S4b) irradiation. An intuitive current increment with different light conditions is shown in Figure 3a with the presence of 5 mM glucose
Figure 2. (a) Absorption spectra and (b) SERS profile of R6G probe molecule on TiO2, Au NPs@TiO2, and Au NRs@TiO2 films. (c,d) Top view of FEM-simulated electrical field intensity distribution polarized along the x-axis on Au NRs@TiO2 and Au NPs@TiO2, respectively.
enormous possibility of using solar light for catalytic reactions. LSPR of Au NPs@TiO2 and Au NRs@TiO2 films was also verified by surface enhanced Raman spectra (SERS). Typical vibrational modes of R6G probe molecule at 1182, 1310, 1361, 1507, and 1647 cm−1 were observed in Raman spectra (Figure 2b). The peak at 1182 cm−1 refers to N−H in-plane vibration and all the other peaks correspond to the C−C breathing modes.21 SERS spectra of bare TiO2 and Au@TiO2 films validate that an enhanced EM field is formed in the vicinity of the Au nanostructures. The periodically patterned Au NRs with a larger particle size show stronger SERS signal than Au NPs, suggesting a stronger EM field and improved sensing of organic molecules for Au NRs than Au NPs.14 This SERS experimental result agrees well with FEM simulation. Photoelectrochemical glucose detection was initially characterized by performing cyclic voltammetry (CV) of bare TiO2 and Au@TiO2 films in PBS solution (Figure S2a) to determine background current. For Au@TiO2 films, a pair of redox peaks appear at about 0.6 and 0.38 V that are ascribed to Au oxidation and reduction in PBS, respectively. A peak located at about 0 V for oxygen reduction reaction (ORR) is also identified, indicating good electrochemical activity of Au nanostructures in PBS. CV testing for a 5 mM glucose solution in PBS shows three strong peaks for Au@TiO2 films, depending on glucose oxidation, around −0.19, 0.4, and 0.52 V (Figure S2b,c). The current densities of these glucose oxidation peaks are more than 2 orders of magnitude higher than the background current density, indicating good biosensing performance by the patterned Au nanostructures. The oxidation peak at −0.19 V is attributed to the conversion from glucose to gluconolactone, and the oxidation peak around 0.52 V is due to further oxidation of gluconolactone to gluconic acid.22 The oxidation peak located at 0.4 V in the cathodic scan generally occurs as a result of indirect oxidation by AuOH sites on the Au nanorod surface formed during the reduction process.2 The oxide layer formed on the surface of Au covers the active sites for glucose oxidation during anodic scan, which leads to a decrease in current. In the cathodic scan, a reduction of Au oxide happens,
Figure 3. (a,c) CV curves of Au NRs@TiO2 electrode collected in 5 mM glucose (lactose) solution in the absence and presence of simulated solar and blue light. (b,d) Corresponding linear relationship of peak current intensity to glucose (lactose) concentration at 0.4 V from the CV curves.
solution. Noticeably, the output signal under blue light is much stronger than the other two conditions, which confirms the photoabsorption spectra and FEM simulation results that an optimal LSPR and maximum electron−hole separation occurs under blue light irradiation. Peak current densities increase linearly with glucose concentrations from 0 to 10 mM (current at 0.4 V is adopted, Figure 3b). An increased current response C
DOI: 10.1021/acssensors.7b00251 ACS Sens. XXXX, XXX, XXX−XXX
Letter
ACS Sensors to 103% and 433% is observed by solar and blue light assisted conditions, respectively, due to LSPR. Additionally, the blue light may contribute to suppress the excitation of TiO2 substrate, which may cause “hot” electron recombination and deteriorate charge separation on the Au surface. A similar performance is found when testing in lactose based PBS solution for Au NRs@TiO2 films. Oxidation of lactose is suppressed, shifting the potential in a positive direction compared to glucose, especially under solar and blue light illumination (Figure S5). The reaction peaks at around 0, 0.7, and 0.45 V are attributed to the production of lactone, hydrolysis of lactone to lactobionic acid, and indirect oxidation, respectively. D-Lactose is a reducing disaccharide, which combines D-galactose and D-glucose monomer units. Oxidation mainly occurs on the D-glucose end of the disaccharide because of faster reaction kinetics of glucose, as well as an easier desorption of D-gluconic acid from Au surface.3,25 However, the larger disaccharide molecule eventually suppresses oxidation, displaying a lower current output than pure glucose detection (Figure S4 and Figure S5). Additional side reactions due to Dgalactose oxidation can also be found at a more positive potential of around 0.8 V, especially under solar light irradiation. An increase in temperature occurred due to the red portion of solar light irradiation, thereby accelerated the rate of conversion of D-galactose for the Au NRs@TiO2 film (Figure S5b).25 Blue light conditions provided the best overall reaction rate performance of D-glucose consumption during lactose detection (Figure S5c). According to the aforementioned analysis, the Au NRs@TiO2 film presents clear quantitative detection abilities for D-glucose and D-lactose. Additionally, the system reaches an optimal LSPR state and detecting condition by carefully tuning external irradiation to blue light. An amperometric (i−t) technique was also utilized to evaluate glucose biosensing activity on the Au NRs@TiO2 film (Figure 4). Current density measured at 0.4 V increases considerably by increasing glucose concentration from 1 μM to 10 mM (Figure S6a,b and Figure 4a,b). A rapid and stable response is observed at glucose concentrations greater than 0.5 mM. Further solar and blue light-assisted amperometric (i−t) measurements demonstrate significantly enhanced chronoamperometric signals under light irradiation. The linear current density increase with glucose concentrations is depicted by the formulas in Figure 4b. A high sensitivity of 812 μA mM−1 cm−2 with a detection limit of 1 μM is achieved for the Au NRs@ TiO2 nanobiosensor under blue light assistance, which is superior to other biosensing systems (Table S1). The detection limit presented here is considered under the lower concentration range of normal physiological glucose levels found in human sweat (5.5 μM).26 Control experiments carried out for lactose gives the best sensitivity of 270 μA mM−1 cm−2 with a detection limit of 10 μM (Figure S6c,d and Figure 4c,d). That is also superior to the state-of-the-art lactose biosensors (Table S2). Selectivity of the Au NRs@TiO2 heterostructure was also characterized by successively adding various interfering species, including human body equivalent ascorbic acid (AA), acetic acid (CA), uric acid (UA), Na+, K+, and Ca2+ to 1 mM glucose (lactose) solution (Figure 4e,f). The induced current by the interfering species is negligible when considering the current density of glucose (lactose) oxidation at a concentration of 1 mM, which is lower than physiological levels (3−8 mM).15 This indicates that glucose (lactose) detection using the Au
Figure 4. (a,c) Amperometric responses of Au NRs@TiO2 electrode at 0.4 V for successive additions of 1−50 μM glucose (10−50 μM lactose). (b,d) Corresponding calibration curves for the absence and presence of solar light and blue light illumination. (e,f) Current response upon addition of various interfering species in 1 mM glucose and lactose, respectively.
NRs@TiO2 plasmonic film suffers minimal interference from other species in the human body. Long-term stability testing over 8 weeks in 5 mM glucose and lactose solution revealed that 94% of incipient sensitivity can be maintained for the Au NRs@TiO2 film even after storing in air (Figure S7). This confirms that the rationally designed Au NRs@TiO 2 architecture has high structural stability and can be used for long-duration applications. Additionally, it is feasible to integrate these facile and effective Au NRs@TiO2 films into already developed sensing technologies,27,28 offering the ability to reduce cost at the same time as increasing specificity and selectivity of the devices. In summary, we systematically explored the shape dependent PEC activity of periodically pattered Au NRs and NPs on TiO2 nanocavities for glucose and lactose detection. The present findings clearly reveal that this facile anodization, sputtering, and thermal dewetting nanomanufacturing process can be accurately controlled to fabricate patterned planar architectures with high surface area, contributing to enhanced charge separation and transfer properties. Au NRs@TiO2 films exhibit significantly more activity than the Au NPs@TiO2 film due to stronger LSPR on Au NRs surfaces. Also, blue light irradiation has proven to be more efficient for photocurrent enhancement by suppressing side reactions during glucose (lactose) oxidation. The aforementioned unique features enable Au NRs@TiO2 films to improve sensitivity, decrease detection limits, provide long-term stability, and good selectivity for nanobiosensing of glucose and lactose. D
DOI: 10.1021/acssensors.7b00251 ACS Sens. XXXX, XXX, XXX−XXX
Letter
ACS Sensors
■
(12) Akhtar, M. S.; Ahmad, A.; Bhakuni, V. Guanidinium Chlorideand Urea-Induced Unfolding of the Dimeric Enzyme Glucose Oxidase. Biochemistry 2002, 41, 3819−3827. (13) Libertino, S.; Aiello, V.; Scandurra, A.; Renis, M.; Sinatra, F. Immobilization of the Enzyme Glucose Oxidase on Both Bulk and Porous SiO2 Surfaces. Sensors 2008, 8, 5637. (14) Sarkar, P.; Pal, P. S.; Ghosh, D.; Setford, S. J.; Tothill, I. E. Amperometric biosensors for detection of the prostate cancer marker (PSA). Int. J. Pharm. 2002, 238, 1−9. (15) Yang, Q.; Long, M.; Tan, L.; Zhang, Y.; Ouyang, J.; Liu, P.; Tang, A. Helical TiO2 Nanotube Arrays Modified by Cu-Cu2O with Ultrahigh Sensitivity for the Nonenzymatic Electro-oxidation of Glucose. ACS Appl. Mater. Interfaces 2015, 7, 12719−12730. (16) Ilkhani, H.; Sarparast, M.; Noori, A.; Zahra Bathaie, S.; Mousavi, M. F. Electrochemical aptamer/antibody based sandwich immunosensor for the detection of EGFR, a cancer biomarker, using gold nanoparticles as a signaling probe. Biosens. Bioelectron. 2015, 74, 491− 497. (17) Catchpole, K. R.; Polman, A. Plasmonic solar cells. Opt. Express 2008, 16, 21793−21800. (18) Liu, Y.; Zhou, J.; Yuan, X.; Jiang, T.; Petti, L.; Zhou, L.; Mormile, P. Hydrothermal synthesis of gold polyhedral nanocrystals by varying surfactant concentration and their LSPR and SERS properties. RSC Adv. 2015, 5, 68668−68675. (19) Juvé, V.; Cardinal, M. F.; Lombardi, A.; Crut, A.; Maioli, P.; Pérez-Juste, J.; Liz-Marzán, L. M.; Del Fatti, N.; Vallée, F. Sizedependent surface plasmon resonance broadening in nonspherical nanoparticles: single gold nanorods. Nano Lett. 2013, 13, 2234−2240. (20) McMahon, J. M.; Schatz, G. C.; Gray, S. K. Plasmonics in the ultraviolet with the poor metals Al, Ga, In, Sn, Tl, Pb, and Bi. Phys. Chem. Chem. Phys. 2013, 15, 5415−5423. (21) Pristinski, D.; Tan, S.; Erol, M.; Du, H.; Sukhishvili, S. In situ SERS study of Rhodamine 6G adsorbed on individually immobilized Ag nanoparticles. J. Raman Spectrosc. 2006, 37, 762−770. (22) Kong, F.-Y.; Li, X.-R.; Zhao, W.-W.; Xu, J.-J.; Chen, H.-Y. Graphene oxide-thionine-Au nanostructure composites: Preparation and applications in non-enzymatic glucose sensing. Electrochem. Commun. 2012, 14, 59−62. (23) Zhang, Y.; Xu, F.; Sun, Y.; Guo, C.; Cui, K.; Shi, Y.; Li, Z. SeedMediated Synthesis of Au Nanocages and Their Electrocatalytic Activity towards Glucose Oxidation. Chem. - Eur. J. 2010, 16, 9248− 9256. (24) Wang, J.; Gong, J.; Xiong, Y.; Yang, J.; Gao, Y.; Liu, Y.; Lu, X.; Tang, Z. Shape-dependent electrocatalytic activity of monodispersed gold nanocrystals toward glucose oxidation. Chem. Commun. 2011, 47, 6894−6896. (25) Ö nal, Y.; Schimpf, S.; Claus, P. Structure sensitivity and kinetics of d-glucose oxidation to d-gluconic acid over carbon-supported gold catalysts. J. Catal. 2004, 223, 122−133. (26) Munje, R.; Muthukumar, S.; Prasad, S. Lancet-free and label-free diagnostics of glucose in sweat using Zinc Oxide based flexible bioelectronics. Sens. Actuators, B 2017, 238, 482−490. (27) Liang, K.; Li, L.; Yang, Y. Inorganic Porous Films for Renewable Energy Storage. ACS Energy Letters 2017, 2, 373−390. (28) Wang, S.; Chinnasamy, T.; Lifson, M.; Inci, F.; Demirci, U. Flexible Substrate-Based Devices for Point-of-Care Diagnostics. Trends Biotechnol. 2016, 34, 909−921.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssensors.7b00251. Experimental section; morphological, structural, and electrochemical characterizations of the Au@TiO2 films (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail
[email protected]. ORCID
Le Zhou: 0000-0001-8327-6667 Yang Yang: 0000-0002-4410-6021 Notes
The authors declare no competing financial interest.
■ ■
ACKNOWLEDGMENTS This work was financially supported by the University of Central Florida through a startup grant (No. 20080741). REFERENCES
(1) Aoun, S. B.; Dursun, Z.; Koga, T.; Bang, G. S.; Sotomura, T.; Taniguchi, I. Effect of metal ad-layers on Au(111) electrodes on electrocatalytic oxidation of glucose in an alkaline solution. J. Electroanal. Chem. 2004, 567, 175−183. (2) Al-Ogaidi, I.; Gou, H.; Al-kazaz, A. K. A.; Aguilar, Z. P.; Melconian, A. K.; Zheng, P.; Wu, N. A gold@silica core-shell nanoparticle-based surface-enhanced Raman scattering biosensor for label-free glucose detection. Anal. Chim. Acta 2014, 811, 76−80. (3) Li, F.; Li, Y.; Feng, J.; Dong, Y.; Wang, P.; Chen, L.; Chen, Z.; Liu, H.; Wei, Q. Ultrasensitive amperometric immunosensor for PSA detection based on Cu2O@CeO2-Au nanocomposites as integrated triple signal amplification strategy. Biosens. Bioelectron. 2017, 87, 630− 637. (4) Huang, X.; Ren, J. Gold nanoparticles based chemiluminescent resonance energy transfer for immunoassay of alpha fetoprotein cancer marker. Anal. Chim. Acta 2011, 686, 115−120. (5) Fan, Z.; Shelton, M.; Singh, A. K.; Senapati, D.; Khan, S. A.; Ray, P. C. Multifunctional Plasmonic Shell-Magnetic Core Nanoparticles for Targeted Diagnostics, Isolation, and Photothermal Destruction of Tumor Cells. ACS Nano 2012, 6, 1065−1073. (6) Zhang, X.; Chen, Y. L.; Liu, R. S.; Tsai, D. P. Plasmonic photocatalysis. Rep. Prog. Phys. 2013, 76, 046401. (7) Zebda, A.; Gondran, C.; Le Goff, A.; Holzinger, M.; Cinquin, P.; Cosnier, S. Mediatorless high-power glucose biofuel cells based on compressed carbon nanotube-enzyme electrodes. Nat. Commun. 2011, 2, 370. (8) Zhang, C.; Ni, H.; Chen, R.; Zhan, W.; Liu, S.; Zhang, B.; Lei, R.; Zha, Y. Enzyme-free Glucose Sensor Fabricated by Nanorods Decorated Nanopore Arrays on Biomedical Stainless Steel. Electroanalysis 2016, 28, 794−799. (9) Jin, J.; Ge, Y.; Zheng, G.; Cai, Y.; Liu, W.; Hui, G. d-Glucose, dGalactose, and d-Lactose non-enzyme quantitative and qualitative analysis method based on Cu foam electrode. Food Chem. 2015, 175, 485−493. (10) Gürsoy, O.; Ç elik, G.; Gürsoy, S. Ş. Electrochemical Biosensor Based on surfactant doped polypyrrole (PPy) matrix for lactose determination. J. Appl. Polym. Sci. 2014, 131, 40200. (11) Campos, P. P.; Moraes, M. L.; Volpati, D.; Miranda, P. B.; Oliveira, O. N., Jr; Ferreira, M. Amperometric detection of lactose using β-galactosidase immobilized in layer-by-layer films. ACS Appl. Mater. Interfaces 2014, 6, 11657−11664. E
DOI: 10.1021/acssensors.7b00251 ACS Sens. XXXX, XXX, XXX−XXX
