Nanoporous gold prepared by dealloying Au:Ag alloys has recently become an attractive material in the field of analytical chemistry. This conductive material has an open, 3D porous framework consisting of nanosized pores and ligaments with surface areas that are 10s to 100s of times larger than planar gold of an equivalent geometric area. The high surface area coupled with an open pore network makes nanoporous gold an ideal support for the development of chemical sensors. Important attributes include conductivity, high surface area, ease of preparation and modification, tunable pore size, and a bicontinuous open pore network. In this paper, the fabrication, characterization, and applications of nanoporous gold in chemical sensing are reviewed specifically as they relate to the development of immunosensors, enzyme-based biosensors, DNA sensors, Raman sensors, and small molecule sensors. 1. Introduction High surface area nanostructured electrodes have received considerable attention in recent years [1–18]. These materials are conductive, have surface areas that are typically 2–1000 times larger than a planar electrode of similar size, and consist of either oriented, well-defined or random pore morphology. Such high surface areas are important to a number of applications, particularly those in the field of chemical sensing when the goal is to improve sensitivity and lower detection limits. In electroanalytical chemistry, for example, the increased surface area can lead to a greater amount of an immobilized reagent on the surface. This can potentially lead to larger currents, even for diffusing species, because Faradaic current typically scales linearly with electrode area; a significantly larger electrode area can potentially yield better S/N ratios, enhanced sensitivity, and lower detection limits. High surface area noble metal electrodes have been fabricated using a number of different approaches including hard templating of latex spheres or SiO2 spheres [7, 8, 19, 20], chemical dealloying [9, 21], electrochemical dealloying [22, 23], H2 bubble formation [24], electrodeposition in the pores of nanopore membranes [1, 2] as well as from ensembles of gold nanoparticles [5, 6], gold microparticles [25, 26], and electrospun gold nanofibers [3, 4]. Each approach has its unique advantages and disadvantages. Figure 1 shows simple examples of different types of high surface area, nanostructured electrodes. Figure 1: Some examples of high surface area nanostructured gold electrodes. The focus of this paper is on nanoporous gold electrodes, particularly those
References
[1]
F. Schr？per, D. Brüggemann, Y. Mourzina, B. Wolfrum, A. Offenh？usser, and D. Mayer, “Analyzing the electroactive surface of gold nanopillars by electrochemical methods for electrode miniaturization,” Electrochimica Acta, vol. 53, no. 21, pp. 6265–6272, 2008.
[2]
C. Shin, W. Shin, and H. G. Hong, “Electrochemical fabrication and electrocatalytic characteristics studies of gold nanopillar array electrode (AuNPE) for development of a novel electrochemical sensor,” Electrochimica Acta, vol. 53, no. 2, pp. 720–728, 2007.
[3]
S. J. H. Fathima, J. Paul, and S. Valiyaveettil, “Surface-structured gold-nanotube mats: fabrication, characterization, and application in surface-enhanced Raman scattering,” Small, vol. 6, no. 21, pp. 2443–2447, 2010.
[4]
S. Marx, M. V. Jose, J. D. Andersen, and A. J. Russell, “Electrospun gold nanofiber electrodes for biosensors,” Biosensors & Bioelectronics, vol. 26, no. 6, pp. 2981–2986, 2011.
[5]
M. Kim, G. H. Jeong, K. Y. Lee, K. Kwon, and S. W. Han, “Fabrication of nanoporous superstructures through hierarchical self-assembly of nanoparticles,” Journal of Materials Chemistry, vol. 18, no. 19, pp. 2208–2212, 2008.
[6]
K. Murata, K. Kajiya, M. Nukaga et al., “A simple fabrication method for three-dimensional gold nanoparticle electrodes and their application to the study of the direct electrochemistry of cytochrome C,” Electroanalysis, vol. 22, no. 2, pp. 185–190, 2010.
[7]
B. Zhao and M. M. Collinson, “Hierarchical porous gold electrodes: preparation, characterization, and electrochemical behavior,” Journal of Electroanalytical Chemistry, vol. 684, pp. 53–59, 2012.
[8]
P. N. Bartlett, J. J. Baumberg, P. R. Birkin, M. A. Ghanem, and M. C. Netti, “Highly ordered macroporous gold and platinum films formed by electrochemical deposition through templates assembled from submicron diameter monodisperse polystyrene spheres,” Chemistry of Materials, vol. 14, no. 5, pp. 2199–2208, 2002.
[9]
Y. Ding, Y. J. Kim, and J. Erlebacher, “Nanoporous gold leaf: “ancient technology”/advanced material,” Advanced Materials, vol. 16, no. 21, pp. 1897–1900, 2004.
[10]
A. S. Aricò, P. Bruce, B. Scrosati, J. M. Tarascon, and W. Van Schalkwijk, “Nanostructured materials for advanced energy conversion and storage devices,” Nature Materials, vol. 4, no. 5, pp. 366–377, 2005.
[11]
T. Asefa, C. T. Duncan, and K. K. Sharma, “Recent advances in nanostructured chemosensors and biosensors,” Analyst, vol. 134, no. 10, pp. 1980–1990, 2009.
[12]
Z. H. Dai and H. X. Ju, “Bioanalysis based on nanoporous materials,” Trends in Analytical Chemistry, vol. 39, pp. 149–162, 2012.
[13]
N. Menzel, E. Ortel, R. Kraehnert, and P. Strasser, “Electrocatalysis using porous nanostructured materials,” Chemphyschem, vol. 13, pp. 1385–1394, 2012.
[14]
S. Park, H. C. Kim, and T. D. Chung, “Electrochemical analysis based on nanoporous structures,” Analyst, vol. 137, no. 17, pp. 3891–3903, 2012.
[15]
E. Seker, M. L. Reed, and M. R. Begley, “Nanoporous gold: fabrication, characterization, and applications,” Materials, vol. 2, no. 4, pp. 2188–2215, 2009.
[16]
A. Walcarius and A. Kuhn, “Ordered porous thin films in electrochemical analysis,” Trends in Analytical Chemistry, vol. 27, no. 7, pp. 593–603, 2008.
[17]
A. Wittstock, J. Biener, and M. B？umer, “Nanoporous gold: a new material for catalytic and sensor applications,” Physical Chemistry Chemical Physics, vol. 12, no. 40, pp. 12919–12930, 2010.
[18]
Y. Yamauchi and K. Kuroda, “Rational design of mesoporous metals and related nanomaterials by a soft-template approach,” Chemistry, vol. 3, no. 4, pp. 664–676, 2008.
[19]
P. N. Bartlett, P. R. Birkin, and M. A. Ghanem, “Electrochemical deposition of macroporous platinum, palladium and cobalt films using polystyrene latex sphere templates,” Chemical Communications, no. 17, pp. 1671–1672, 2000.
[20]
J. Wijnhoven, S. J. M. Zevenhuizen, M. A. Hendriks, D. Vanmaekelbergh, J. J. Kelly, and W. L. Vos, “Electrochemical assembly of ordered macropores in gold,” Advanced Materials, vol. 12, no. 12, pp. 888–890, 2000.
[21]
F. L. Jia, C. F. Yu, K. J. Deng, and L. Z. Zhang, “Nanoporous metal (Cu, Ag, Au) films with high surface area: General fabrication and preliminary electrochemical performance,” Journal of Physical Chemistry C, vol. 111, no. 24, pp. 8424–8431, 2007.
[22]
K. Sieradzki, N. Dimitrov, D. Movrin, C. McCall, N. Vasiljevic, and J. Erlebacher, “The dealloying critical potential,” Journal of the Electrochemical Society, vol. 149, no. 8, pp. B370–B377, 2002.
[23]
K. Wagner, S. R. Brankovic, N. Dimitrov, and K. Sieradzki, “Dealloying below the critical potential,” Journal of the Electrochemical Society, vol. 144, no. 10, pp. 3545–3555, 1997.
[24]
W. Huang, M. Wang, J. Zheng, and Z. Li, “Facile fabrication of multifunctional three-dimensional hierarchical porous gold films via surface rebuilding,” Journal of Physical Chemistry C, vol. 113, no. 5, pp. 1800–1805, 2009.
[25]
S. J. Guo, S. J. Dong, and E. K. Wang, “Monodisperse raspberry-like gold submicrometer spheres: large-scale synthesis and interface assembling for colloid sphere array,” Crystal Growth & Design, vol. 8, no. 10, pp. 3581–3585, 2008.
[26]
Z. H. Li, V. Ravaine, S. Ravaine, P. Garrigue, and A. Kuhn, “Raspberry-like gold microspheres: preparation and electrochemical characterization,” Advanced Functional Materials, vol. 17, no. 4, pp. 618–622, 2007.
[27]
J. Biener, A. Wittstock, T. F. Baumann, J. Weissmuller, M. Baumer, and A. V. Hamza, “Surface chemistry in nanoscale materials,” Materials, vol. 2, no. 4, pp. 2404–2428, 2009.
[28]
J. Weissmüller, R. C. Newman, H. J. Jin, A. M. Hodge, and J. W. Kysar, “Nanoporous metals by alloy corrosion: formation and mechanical properties,” MRS Bulletin, vol. 34, no. 8, pp. 577–586, 2009.
[29]
A. Walcarius, “Template-directed porous electrodes in electroanalysis,” Analytical and Bioanalytical Chemistry, vol. 396, no. 1, pp. 261–272, 2010.
[30]
Y. G. Guo, J. S. Hu, and L. J. Wan, “Nanostructured materials for electrochemical energy conversion and storage devices,” Advanced Materials, vol. 20, no. 23, pp. 2878–2887, 2008.
[31]
A. Wittstock, J. Biener, J. Erlebacher, and M. Baumer, Nanoporous Gold: From an Ancient Technology to a High-Tech Material, Royal Society of Chemistry, 2012.
[32]
G. S. Attard, P. N. Bartlett, N. R. B. Coleman, J. M. Elliott, J. R. Owen, and J. H. Wang, “Mesoporous platinum films from lyotropic liquid crystalline phases,” Science, vol. 278, no. 5339, pp. 838–840, 1997.
[33]
P. R. Birkin, J. M. Elliott, and Y. E. Watson, “Electrochemical reduction of oxygen on mesoporous platinum microelectrodes,” Chemical Communications, no. 17, pp. 1693–1694, 2000.
[34]
H. Boo, S. Park, B. Y. Ku et al., “Ionic strength-controlled virtual area of mesoporous platinum electrode,” Journal of the American Chemical Society, vol. 126, no. 14, pp. 4524–4525, 2004.
[35]
D. H. Nagaraju and V. Lakshminarayanan, “Electrochemically grown mesoporous gold film as high surface area material for electro-oxidation of alcohol in alkaline medium,” Journal of Physical Chemistry C, vol. 113, no. 33, pp. 14922–14926, 2009.
[36]
D. B. Robinson, C. A. M. Wu, M. D. Ong, B. W. Jacobs, and B. E. Pierson, “Effect of electrolyte and adsorbates on charging rates in mesoporous gold electrodes,” Langmuir, vol. 26, no. 9, pp. 6797–6803, 2010.
[37]
B. C. Tappan, S. A. Steiner, and E. P. Luther, “Nanoporous metal foams,” Angewandte Chemie - International Edition, vol. 49, no. 27, pp. 4544–4565, 2010.
[38]
M. C. Dixon, T. A. Daniel, M. Hieda, D. M. Smilgies, M. H. W. Chan, and D. L. Allara, “Preparation, structure, and optical properties of nanoporous gold thin films,” Langmuir, vol. 23, no. 5, pp. 2414–2422, 2007.
[39]
Y. Ding and M. W. Chen, “Nanoporous metals for catalytic and optical applications,” MRS Bulletin, vol. 34, no. 8, pp. 569–576, 2009.
[40]
Z. H. Zhang, Y. Wang, Z. Qi, J. K. Lin, and X. F. Bian, “Nanoporous gold ribbons with bimodal channel size distributions by chemical dealloying of al-au alloys,” Journal of Physical Chemistry C, vol. 113, no. 4, pp. 1308–1314, 2009.
[41]
Z. H. Zhang, Y. Wang, Z. Qi, C. Somsen, X. G. Wang, and C. C. Zhao, “Fabrication and characterization of nanoporous gold composites through chemical dealloying of two phase Al-Au alloys,” Journal of Materials Chemistry, vol. 19, no. 33, pp. 6042–6050, 2009.
[42]
Z. H. Zhang, Y. Wang, Z. Qi, W. H. Zhang, J. Y. Qin, and J. Frenzel, “Generalized fabrication of nanoporous metals (Au, Pd, Pt, Ag, and Cu) through chemical dealloying,” Journal of Physical Chemistry C, vol. 113, no. 29, pp. 12629–12636, 2009.
[43]
M. Hakamada and M. Mabuchi, “Nanoporous gold prism microassembly through a self-organizing route,” Nano Letters, vol. 6, no. 4, pp. 882–885, 2006.
[44]
A. Dursun, D. V. Pugh, and S. G. Corcoran, “A steady-state method for determining the dealloying critical potential,” Electrochemical and Solid-State Letters, vol. 6, no. 8, pp. B32–B34, 2003.
[45]
K. Márquez, R. Ortiz, J. W. Schultze, O. P. Márquez, J. Márquez, and G. Staikov, “In situ FTIR monitoring of Ag and Au electrodeposition on glassy carbon and silicon,” Electrochimica Acta, vol. 48, no. 6, pp. 711–720, 2003.
[46]
B. Bozzini, G. P. De Gaudenzi, and C. Mele, “A SERS investigation of the electrodeposition of Ag-Au alloys from free-cyanide solutions—part II,” Journal of Electroanalytical Chemistry, vol. 570, no. 1, pp. 29–34, 2004.
[47]
B. Bozzini, G. P. De Gaudenzi, and C. Mele, “A SERS investigation of the electrodeposition of Ag-Au alloys from free-cyanide solutions,” Journal of Electroanalytical Chemistry, vol. 563, no. 1, pp. 133–143, 2004.
[48]
C. X. Ji, G. Oskam, Y. Ding, J. D. Erlebacher, A. J. Wagner, and P. C. Searson, “Deposition of AuxAg1-x/AuyAg1-y multilayers and multisegment nanowires,” Journal of the Electrochemical Society, vol. 150, no. 8, pp. C523–C528, 2003.
[49]
W. S. Chae, D. Van Gough, S. K. Ham, D. B. Robinson, and P. V. Braun, “Effect of ordered intermediate porosity on ion transport in hierarchically nanoporous electrodes,” Acs Applied Materials & Interfaces, vol. 4, no. 8, pp. 3973–3979, 2012.
[50]
D. A. McCurry, M. Kamundi, M. Fayette, F. Wafula, and N. Dimitrov, “All electrochemical fabrication of a platinized nanoporous Au thin-film catalyst,” Acs Applied Materials & Interfaces, vol. 3, no. 11, pp. 4459–4468, 2011.
[51]
S. Sattayasamitsathit, A. M. O'Mahony, X. Y. Xiao, et al., “Highly ordered tailored three-dimensional hierarchical nano/microporous gold-carbon architectures,” Journal of Materials Chemistry, vol. 22, pp. 11950–11956, 2012.
[52]
L. Liu, W. Lee, Z. Huang, R. Scholz, and U. G？sele, “Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane,” Nanotechnology, vol. 19, no. 33, Article ID 335604, 2008.
[53]
C. X. Ji and P. C. Searson, “Fabrication of nanoporous gold nanowires,” Applied Physics Letters, vol. 81, no. 23, pp. 4437–4439, 2002.
[54]
C. X. Ji and P. C. Searson, “Synthesis and characterization of nanoporous gold nanowires,” Journal of Physical Chemistry B, vol. 107, no. 19, pp. 4494–4499, 2003.
[55]
R. Laocharoensuk, S. Sattayasamitsathit, J. Burdick, P. Kanatharana, P. Thavarungkul, and J. Wang, “Shape-tailored porous gold nanowires: from nano barbells to nano step-cones,” ACS Nano, vol. 1, no. 5, pp. 403–408, 2007.
[56]
S. H. Yoo and S. Park, “Platinum-coated, nanoporous gold nanorod arrays: synthesis and characterization,” Advanced Materials, vol. 19, no. 12, pp. 1612–1615, 2007.
[57]
X. H. Gu, L. Q. Xu, F. Tian, and Y. Ding, “Au-Ag alloy nanoporous nanotubes,” Nano Research, vol. 2, no. 5, pp. 386–393, 2009.
[58]
E. Seker, M. L. Reed, and M. R. Begley, “A thermal treatment approach to reduce microscale void formation in blanket nanoporous gold films,” Scripta Materialia, vol. 60, no. 6, pp. 435–438, 2009.
[59]
M. Kim, W. J. Ha, J. W. Anh, H. S. Kim, S. W. Park, and D. Lee, “Fabrication of nanoporous gold thin films on silicon substrate by multilayer deposition of Au and Ag,” Journal of Alloys and Compounds, vol. 484, no. 1-2, pp. 28–32, 2009.
[60]
D. Wang and P. Schaaf, “Nanoporous gold nanoparticles,” Journal of Materials Chemistry, vol. 22, pp. 5344–5348, 2012.
[61]
X. L. Quan, L. M. Fischer, A. Boisen, and M. Tenje, “Development of nanoporous gold electrodes for electrochemical applications,” Microelectronic Engineering, vol. 88, no. 8, pp. 2379–2382, 2011.
[62]
M. Kawasaki and M. Iino, “Self-assembly of alkanethiol monolayers on Ag-Au(111) alloy surfaces,” Journal of Physical Chemistry B, vol. 110, no. 42, pp. 21124–21130, 2006.
[63]
E. Seker, Y. Berdichevsky, M. R. Begley, M. L. Reed, K. J. Staley, and M. L. Yarmush, “The fabrication of low-impedance nanoporous gold multiple-electrode arrays for neural electrophysiology studies,” Nanotechnology, vol. 21, no. 12, Article ID 125504, 2010.
[64]
E. Rouya, S. Cattarin, M. L. Reed, R. G. Kelly, and G. Zangari, “Electrochemical characterization of the surface area of nanoporous gold films,” Journal of the Electrochemical Society, vol. 159, no. 4, pp. K97–K102, 2012.
[65]
P. N. Ciesielski, A. M. Scott, C. J. Faulkner, B. J. Berron, D. E. Cliffel, and G. K. Jennings, “Functionalized nanoporous gold leaf electrode films for the immobilization of photosystem I,” ACS Nano, vol. 2, no. 12, pp. 2465–2472, 2008.
[66]
O. V. Shulga, K. Jefferson, A. R. Khan et al., “Preparation and characterization of porous gold and its application as a platform for immobilization of acetylcholine esterase,” Chemistry of Materials, vol. 19, no. 16, pp. 3902–3911, 2007.
[67]
Y. H. Tan, J. A. Davis, K. Fujikawa, N. V. Ganesh, A. V. Demchenko, and K. J. Stine, “Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy,” Journal of Materials Chemistry, vol. 22, no. 14, pp. 6733–6745, 2012.
[68]
J. F. Huang and I. W. Sun, “Fabrication and surface functionalization of nanoporous gold by electrochemical alloying/dealloying of Au-Zn in an ionic liquid, and the self-assembly of L-cysteine monolayers,” Advanced Functional Materials, vol. 15, no. 6, pp. 989–994, 2005.
[69]
J. Snyder, P. Asanithi, A. B. Dalton, and J. Erlebacher, “Stabilized nanoporous metals by dealloying ternary alloy precursors,” Advanced Materials, vol. 20, no. 24, pp. 4883–4886, 2008.
[70]
C. X. Xu, R. Y. Wang, M. W. Chen, Y. Zhang, and Y. Ding, “Dealloying to nanoporous Au/Pt alloys and their structure sensitive electrocatalytic properties,” Physical Chemistry Chemical Physics, vol. 12, no. 1, pp. 239–246, 2010.
[71]
X. G. Wang, J. Z. Sun, C. Zhang, T. Y. Kou, and Z. H. Zhang, “On the microstructure, chemical composition, and porosity evolution of nanoporous alloy through successive dealloying of ternary Al-Pd-Au precursor,” Journal of Physical Chemistry C, vol. 116, no. 24, pp. 13271–13280, 2012.
[72]
X. G. Wang, J. Frenzel, W. M. Wang et al., “Length-scale modulated and electrocatalytic activity enhanced nanoporous gold by doping,” Journal of Physical Chemistry C, vol. 115, no. 11, pp. 4456–4465, 2011.
[73]
J. L. Xu, C. Zhang, X. G. Wang et al., “Fabrication of bi-modal nanoporous bimetallic Pt-Au alloy with excellent electrocatalytic performance towards formic acid oxidation,” Green Chemistry, vol. 13, no. 7, pp. 1914–1922, 2011.
[74]
E. Detsi, S. Punzhin, J. C. Rao, P. R. Onck, and J. T. M. De Hosson, “Enhanced strain in functional nanoporous gold with a dual microscopic length scale structure,” Acs Nano, vol. 6, no. 5, pp. 3734–3744, 2012.
[75]
H. J. Jin, X. L. Wang, S. Parida, K. Wang, M. Seo, and J. Weissmüller, “Nanoporous Au-Pt alloys as large strain electrochemical actuators,” Nano Letters, vol. 10, no. 1, pp. 187–194, 2010.
[76]
M. Kamundi, L. Bromberg, E. Fey, C. Mitchell, M. Fayette, and N. Dimitrov, “Impact of structure and composition on the dealloying of AuxAg(1-x) alloys on the nanoscale,” Journal of Physical Chemistry C, vol. 116, no. 26, pp. 14123–14133, 2012.
[77]
X. Lu, T. J. Balk, R. Spolenak, and E. Arzt, “Dealloying of Au-Ag thin films with a composition gradient: influence on morphology of nanoporous Au,” Thin Solid Films, vol. 515, no. 18, pp. 7122–7126, 2007.
[78]
X. Lu, E. Bischoff, R. Spolenak, and T. J. Balk, “Investigation of dealloying in Au-Ag thin films by quantitative electron probe microanalysis,” Scripta Materialia, vol. 56, no. 7, pp. 557–560, 2007.
[79]
L. Y. Chen, X. Y. Lang, T. Fujita, and M. W. Chen, “Nanoporous gold for enzyme-free electrochemical glucose sensors,” Scripta Materialia, vol. 65, no. 1, pp. 17–20, 2011.
[80]
L. H. Qian and M. W. Chen, “Ultrafine nanoporous gold by low-temperature dealloying and kinetics of nanopore formation,” Applied Physics Letters, vol. 91, no. 8, Article ID 083105, 2007.
[81]
R. Li and K. Sieradzki, “Ductile-brittle transition in random porous Au,” Physical Review Letters, vol. 68, no. 8, pp. 1168–1171, 1992.
[82]
C. McCall, N. Dimitrov, and K. Sieradzki, “Underpotential deposition on alloys,” Journal of the Electrochemical Society, vol. 148, no. 6, pp. E290–E293, 2001.
[83]
J. Snyder, K. Livi, and J. Erlebacher, “Dealloying silver/gold alloys in neutral silver nitrate solution: porosity evolution, surface composition, and surface oxides,” Journal of the Electrochemical Society, vol. 155, no. 8, pp. C464–C473, 2008.
[84]
N. A. Senior and R. C. Newman, “Synthesis of tough nanoporous metals by controlled electrolytic dealloying,” Nanotechnology, vol. 17, no. 9, pp. 2311–2316, 2006.
[85]
J. Erlebacher and K. Sieradzki, “Pattern formation during dealloying,” Scripta Materialia, vol. 49, no. 10, pp. 991–996, 2003.
[86]
E. Detsi, M. van de Schootbrugge, S. Punzhin, P. R. Onck, and J. T. M. De Hosson, “On tuning the morphology of nanoporous gold,” Scripta Materialia, vol. 64, no. 4, pp. 319–322, 2011.
[87]
J. Erlebacher, M. J. Aziz, A. Karma, N. Dimitrov, and K. Sieradzki, “Evolution of nanoporosity in dealloying,” Nature, vol. 410, no. 6827, pp. 450–453, 2001.
[88]
J. Erlebacher, “An atomistic description of dealloying porosity evolution, the critical potential, and rate-limiting behavior,” Journal of the Electrochemical Society, vol. 151, no. 10, pp. C614–C626, 2004.
[89]
S. Parida, D. Kramer, C. A. Volkert, H. R？sner, J. Erlebacher, and J. Weissmüller, “Volume change during the formation of nanoporous gold by dealloying,” Physical Review Letters, vol. 97, no. 3, Article ID 035504, 2006.
[90]
Y. H. Tan, J. R. Schallom, N. V. Ganesh, K. Fujikawa, A. V. Demchenko, and K. J. Stine, “Characterization of protein immobilization on nanoporous gold using atomic force microscopy and scanning electron microscopy,” Nanoscale, vol. 3, no. 8, pp. 3395–3407, 2011.
[91]
T. Fujita, L. H. Qian, K. Inoke, J. Erlebacher, and M. W. Chen, “Three-dimensional morphology of nanoporous gold,” Applied Physics Letters, vol. 92, no. 25, Article ID 251902, 2008.
[92]
H. R？sner, S. Parida, D. Kramer, C. A. Volkert, and J. Weissmüller, “Reconstructing a nanoporous metal in three dimensions: an electron tomography study of dealloyed gold leaf,” Advanced Engineering Materials, vol. 9, no. 7, pp. 535–541, 2007.
[93]
Y. C. K. Chen, Y. S. Chu, J. Yi et al., “Morphological and topological analysis of coarsened nanoporous gold by x-ray nanotomography,” Applied Physics Letters, vol. 96, no. 4, Article ID 043122, 2010.
[94]
Y. C. K. Chen-Wiegart, S. Wang, Y. S. Chu et al., “Structural evolution of nanoporous gold during thermal coarsening,” Acta Materialia, vol. 60, no. 12, pp. 4972–4981, 2012.
[95]
A. Wittstock, B. Neumann, A. Schaefer et al., “Nanoporous Au: an unsupported pure gold catalyst?” Journal of Physical Chemistry C, vol. 113, no. 14, pp. 5593–5600, 2009.
[96]
V. Zielasek, B. Jürgens, C. Schulz et al., “Gold catalysts: nanoporous gold foams,” Angewandte Chemie - International Edition, vol. 45, no. 48, pp. 8241–8244, 2006.
[97]
A. Schaefer, D. Ragazzon, A. Wittstock et al., “Toward controlled modification of nanoporous gold. A detailed surface science study on cleaning and oxidation,” Journal of Physical Chemistry C, vol. 116, no. 7, pp. 4564–4571, 2012.
[98]
Y. Liu, S. Bliznakov, and N. Dimitrov, “Comprehensive study of the application of a pb underpotential deposition-assisted method for surface area measurement of metallic nanoporous materials,” Journal of Physical Chemistry C, vol. 113, no. 28, pp. 12362–12372, 2009.
[99]
E. Detsi, E. De Jong, A. Zinchenko, and Z. Vukovic, “On the specific surface area of nanoporous materials,” Acta Materialia, vol. 59, no. 20, pp. 7488–7497, 2011.
[100]
S. Park, Y. J. Song, J. H. Han, H. Boo, and T. D. Chung, “Structural and electrochemical features of 3D nanoporous platinum electrodes,” Electrochimica Acta, vol. 55, no. 6, pp. 2029–2035, 2010.
[101]
R. Szamocki, A. Velichko, C. Holzapfel et al., “Macroporous ultramicroelectrodes for improved electroanalytical measurements,” Analytical Chemistry, vol. 79, no. 2, pp. 533–539, 2007.
[102]
J. Erlebacher and R. Seshadri, “Hard materials with tunable porosity,” MRS Bulletin, vol. 34, no. 8, pp. 561–568, 2009.
[103]
M. Hakamada and M. Mabuchi, “Thermal coarsening of nanoporous gold: melting or recrystallization,” Journal of Materials Research, vol. 24, no. 2, pp. 301–304, 2009.
[104]
X. Y. Lang, L. Y. Chen, P. F. Guan, T. Fujita, and M. W. Chen, “Geometric effect on surface enhanced Raman scattering of nanoporous gold: improving Raman scattering by tailoring ligament and nanopore ratios,” Applied Physics Letters, vol. 94, no. 21, Article ID 213109, 2009.
[105]
X. Y. Lang, P. F. Guan, T. Fujita, and M. W. Chen, “Tailored nanoporous gold for ultrahigh fluorescence enhancement,” Physical Chemistry Chemical Physics, vol. 13, no. 9, pp. 3795–3799, 2011.
[106]
M. Hakamada, M. Takahashi, and M. Mabuchi, “Enhanced thermal stability of laccase immobilized on monolayer-modified nanoporous Au,” Materials Letters, vol. 66, pp. 4–6, 2012.
[107]
B. Pandey, Y. H. Tan, K. Fujikawa, A. V. Demchenko, and K. J. Stine, “Comparative study of the binding of concanavalin A to self-assembled monolayers containing a thiolated alpha-mannoside on flat gold and on nanoporous gold,” Journal of Carbohydrate Chemistry, vol. 31, no. 4–6, pp. 466–503, 2012.
[108]
H. Qiu, C. Xu, X. Huang, Y. Ding, Y. Qu, and P. Gao, “Immobilization of laccase on nanoporous gold: comparative studies on the immobilization strategies and the particle size effects,” Journal of Physical Chemistry C, vol. 113, no. 6, pp. 2521–2525, 2009.
[109]
O. V. Shulga, D. Zhou, A. V. Demchenko, and K. J. Stine, “Detection of free prostate specific antigen (fPSA) on a nanoporous gold platform,” Analyst, vol. 133, no. 3, pp. 319–322, 2008.
[110]
Y. Chu, B. Seo, and J. Kim, “Electrochemical properties of alkanethiol monolayers adsorbed on nanoporous au surfaces,” Bulletin of the Korean Chemical Society, vol. 31, no. 11, pp. 3407–3410, 2010.
[111]
M. Hakamada, M. Takahashi, T. Furukawa et al., “Electrochemical stability of self-assembled monolayers on nanoporous Au,” Physical Chemistry Chemical Physics, vol. 13, no. 26, pp. 12277–12284, 2011.
[112]
L. V. Moskaleva, S. R？he, A. Wittstock et al., “Silver residues as a possible key to a remarkable oxidative catalytic activity of nanoporous gold,” Physical Chemistry Chemical Physics, vol. 13, no. 10, pp. 4529–4539, 2011.
[113]
A. Wittstock, A. Wichmann, J. Biener, and M. Baumer, “Nanoporous gold: a new gold catalyst with tunable properties,” Faraday Discussions, vol. 152, pp. 87–98, 2011.
[114]
L. Zhang, L. Y. Chen, H. W. Liu et al., “Effect of residual silver on surface-enhanced Raman scattering of dealloyed nanoporous gold,” Journal of Physical Chemistry C, vol. 115, no. 40, pp. 19583–19587, 2011.
[115]
J. Biener, A. Wittstock, M. M. Biener, T. Nowitzki, A. V. Hamza, and M. Baeumer, “Effect of surface chemistry on the stability of gold nanostructures,” Langmuir, vol. 26, no. 17, pp. 13736–13740, 2010.
[116]
M. M. Biener, J. Biener, A. Wichmann et al., “ALD functionalized nanoporous gold: thermal stability, mechanical properties, and catalytic activity,” Nano Letters, vol. 11, no. 8, pp. 3085–3090, 2011.
[117]
Y. Sun and T. J. Balk, “A multi-step dealloying method to produce nanoporous gold with no volume change and minimal cracking,” Scripta Materialia, vol. 58, no. 9, pp. 727–730, 2008.
[118]
G. W. Nyce, J. R. Hayes, A. V. Hamza, and J. H. Satcher, “Synthesis and characterization of hierarchical porous gold materials,” Chemistry of Materials, vol. 19, no. 3, pp. 344–346, 2007.
[119]
Y. Ding and J. Erlebacher, “Nanoporous metals with controlled multimodal pore size distribution,” Journal of the American Chemical Society, vol. 125, no. 26, pp. 7772–7773, 2003.
[120]
M. E. Cox and D. C. Dunand, “Bulk gold with hierarchical macro-, micro- and nano-porosity,” Materials Science and Engineering A, vol. 528, no. 6, pp. 2401–2406, 2011.
[121]
X. M. Li, X. Y. Yang, and S. S. Zhang, “Electrochemical enzyme immunoassay using model labels,” Trends in Analytical Chemistry, vol. 27, no. 6, pp. 543–553, 2008.
[122]
P. B. Luppa, L. J. Sokoll, and D. W. Chan, “Immunosensors—principles and applications to clinical chemistry,” Clinica Chimica Acta, vol. 314, no. 1-2, pp. 1–26, 2001.
[123]
N. J. Ronkainen, H. B. Halsall, and W. R. Heineman, “Electrochemical biosensors,” Chemical Society Reviews, vol. 39, no. 5, pp. 1747–1763, 2010.
[124]
C. F. Ding, H. Li, K. C. Hu, and J. M. Lin, “Electrochemical immunoassay of hepatitis B surface antigen by the amplification of gold nanoparticles based on the nanoporous gold electrode,” Talanta, vol. 80, no. 3, pp. 1385–1391, 2010.
[125]
R. Li, D. Wu, H. Li et al., “Label-free amperometric immunosensor for the detection of human serum chorionic gonadotropin based on nanoporous gold and graphene,” Analytical Biochemistry, vol. 414, no. 2, pp. 196–201, 2011.
[126]
B. Y. Zhao, Q. Wei, C. Xu et al., “Label-free electrochemical immunosensor for sensitive detection of kanamycin,” Sensors and Actuators B, vol. 155, no. 2, pp. 618–625, 2011.
[127]
Q. Wei, Y. F. Zhao, C. X. Xu et al., “Nanoporous gold film based immunosensor for label-free detection of cancer biomarker,” Biosensors & Bioelectronics, vol. 26, no. 8, pp. 3714–3718, 2011.
[128]
M. Zhang, S. G. Ge, W. P. Li et al., “Ultrasensitive electrochemiluminescence immunoassay for tumor marker detection using functionalized Ru-silica@nanoporous gold composite as labels,” Analyst, vol. 137, no. 3, pp. 680–685, 2012.
[129]
S. G. Ge, X. L. Jiao, and D. R. Chen, “Ultrasensitive electrochemical immunosensor for CA 15-3 using thionine-nanoporous gold-graphene as a platform and horseradish peroxidase-encapsulated liposomes as signal amplification,” Analyst, vol. 137, pp. 4440–4447, 2012.
[130]
K. C. Hu, D. X. Lan, X. M. Li, and S. S. Zhang, “Electrochemical DNA biosensor based on nanoporous gold electrode and multifunctional encoded DNA-Au bio bar codes,” Analytical Chemistry, vol. 80, no. 23, pp. 9124–9130, 2008.
[131]
K. C. Hu, P. Liu, S. J. Ye, and S. S. Zhang, “Ultrasensitive electrochemical detection of DNA based on PbS nanoparticle tags and nanoporous gold electrode,” Biosensors & Bioelectronics, vol. 24, no. 10, pp. 3113–3119, 2009.
[132]
X. F. Hu, R. Y. Wang, Y. Ding, X. L. Zhang, and W. R. Jin, “Electrochemiluminescence of CdTe quantum dots as labels at nanoporous gold leaf electrodes for ultrasensitive DNA analysis,” Talanta, vol. 80, no. 5, pp. 1737–1743, 2010.
[133]
M. Yan, M. Zhang, S. G. Ge et al., “Ultrasensitive electrochemiluminescence detection of DNA based on nanoporous gold electrode and PdCu@carbon nanocrystal composites as labels,” Analyst, vol. 137, pp. 3314–3320, 2012.
[134]
M. Hakamada, M. Takahashi, and M. Mabuchi, “Enzyme electrodes stabilized by monolayer-modified nanoporous Au for biofuel cells,” Gold Bulletin, vol. 45, no. 1, pp. 9–15, 2012.
[135]
M. D. Scanlon, U. Salaj-Kosla, S. Belochapkine et al., “Characterization of nanoporous gold electrodes for bioelectrochemical applications,” Langmuir, vol. 28, no. 4, pp. 2251–2261, 2012.
[136]
V. Vamvakaki and N. A. Chaniotakis, “Immobilization of enzymes into nanocavities for the improvement of biosensor stability,” Biosensors & Bioelectronics, vol. 22, no. 11, pp. 2650–2655, 2007.
[137]
S. Sotiropoulou, V. Vamvakaki, and N. A. Chaniotakis, “Stabilization of enzymes in nanoporous materials for biosensor applications,” Biosensors & Bioelectronics, vol. 20, no. 8, pp. 1674–1679, 2005.
[138]
H. Qiu, C. Xu, X. Huang, Y. Ding, Y. Qu, and P. Gao, “Adsorption of lacease on the surface of nanoporous gold and the direct electron transfer between them,” Journal of Physical Chemistry C, vol. 112, no. 38, pp. 14781–14785, 2008.
[139]
X. Wang, X. Y. Liu, X. L. Yan, P. Zhao, Y. Ding, and P. Xu, “Enzyme-nanoporous gold biocomposite: excellent biocatalyst with improved biocatalytic performance and stability,” Plos One, vol. 6, no. 9, Article ID e24207, 2011.
[140]
L. Y. Chen, T. Fujita, and M. W. Chen, “Biofunctionalized nanoporous gold for electrochemical biosensors,” Electrochimica Acta, vol. 67, pp. 1–5, 2012.
[141]
H. J. Qiu, L. Y. Xue, G. L. Ji et al., “Enzyme-modified nanoporous gold-based electrochemical biosensors,” Biosensors & Bioelectronics, vol. 24, no. 10, pp. 3014–3018, 2009.
[142]
X. L. Yan, X. Wang, P. Zhao, Y. Zhang, P. Xu, and Y. Ding, “Xylanase immobilized nanoporous gold as a highly active and stable biocatalyst,” Microporous and Mesoporous Materials, vol. 161, pp. 1–6, 2012.
[143]
H. J. Qiu, Y. Li, G. L. Ji et al., “Immobilization of lignin peroxidase on nanoporous gold: enzymatic properties and in situ release of H2O2 by co-immobilized glucose oxidase,” Bioresource Technology, vol. 100, no. 17, pp. 3837–3842, 2009.
[144]
H. J. Qiu, G. P. Zhou, G. L. Ji, Y. Zhang, X. R. Huang, and Y. Ding, “A novel nanoporous gold modified electrode for the selective determination of dopamine in the presence of ascorbic acid,” Colloids and Surfaces B, vol. 69, no. 1, pp. 105–108, 2009.
[145]
F. H. Meng, X. L. Yan, J. G. Liu, J. Gu, and Z. G. Zou, “Nanoporous gold as non-enzymatic sensor for hydrogen peroxide,” Electrochimica Acta, vol. 56, no. 12, pp. 4657–4662, 2011.
[146]
X. B. Ge, L. Q. Wang, Z. N. Liu, and Y. Ding, “Nanoporous gold leaf for amperometric determination of nitrite,” Electroanalysis, vol. 23, no. 2, pp. 381–386, 2011.
[147]
Z. N. Liu, H. C. Zhang, S. F. Hou, and H. Y. Ma, “Highly sensitive and selective electrochemical detection of L-cysteine using nanoporous gold,” Microchimica Acta, vol. 177, no. 3-4, pp. 427–433, 2012.
[148]
Z. N. Liu, H. C. Zhang, H. Y. Ma, and S. F. Hou, “Selective determination of p-nitrophenol based on its unique voltammetric behavior on nanoporous gold,” Electroanalysis, vol. 23, no. 12, pp. 2851–2861, 2011.
[149]
Z. N. Liu, J. G. Du, C. C. Qiu et al., “Electrochemical sensor for detection of p-nitrophenol based on nanoporous gold,” Electrochemistry Communications, vol. 11, no. 7, pp. 1365–1368, 2009.
[150]
X. L. Yan, F. H. Meng, S. Z. Cui, J. G. Liu, J. Gu, and Z. G. Zou, “Effective and rapid electrochemical detection of hydrazine by nanoporous gold,” Journal of Electroanalytical Chemistry, vol. 661, no. 1, pp. 44–48, 2011.
[151]
Q. Li, S. Cui, and X. Yan, “Electrocatalytic oxidation of glucose on nanoporous gold membranes,” Journal of Solid State Electrochemistry, vol. 16, no. 3, pp. 1099–1104, 2012.
[152]
S. Park, H. Boo, and T. D. Chung, “Electrochemical non-enzymatic glucose sensors,” Analytica Chimica Acta, vol. 556, no. 1, pp. 46–57, 2006.
[153]
K. E. Toghill and R. G. Compton, “Electrochemical non-enzymatic glucose sensors: a perspective and an evaluation,” International Journal of Electrochemical Science, vol. 5, no. 9, pp. 1246–1301, 2010.
[154]
H. Yin, C. Zhou, C. Xu, P. Liu, X. Xu, and Y. Ding, “Aerobic oxidation of D-glucose on support-free nanoporoug gold,” Journal of Physical Chemistry C, vol. 112, no. 26, pp. 9673–9678, 2008.
[155]
Z. N. Liu, L. H. Huang, L. L. Zhang, H. Y. Ma, and Y. Ding, “Electrocatalytic oxidation of d-glucose at nanoporous Au and Au-Ag alloy electrodes in alkaline aqueous solutions,” Electrochimica Acta, vol. 54, no. 28, pp. 7286–7293, 2009.
[156]
B. Seo and J. Kim, “Electrooxidation of glucose at nanoporous gold surfaces: structure dependent electrocatalysis and its application to amperometric detection,” Electroanalysis, vol. 22, no. 9, pp. 939–945, 2010.
[157]
Y. Xia, W. Huang, J. Zheng, Z. Niu, and Z. Li, “Nonenzymatic amperometric response of glucose on a nanoporous gold film electrode fabricated by a rapid and simple electrochemical method,” Biosensors & Bioelectronics, vol. 26, no. 8, pp. 3555–3561, 2011.
[158]
X. Y. Lang, P. F. Guan, L. Zhang, T. Fujita, and M. W. Chen, “Characteristic length and temperature dependence of surface enhanced raman scattering of nanoporous gold,” Journal of Physical Chemistry C, vol. 113, no. 25, pp. 10956–10961, 2009.
[159]
L. H. Qian, A. Inoue, and M. W. Chen, “Large surface enhanced Raman scattering enhancements from fracture surfaces of nanoporous gold,” Applied Physics Letters, vol. 92, no. 9, Article ID 093113, 2008.
[160]
L. H. Qian, X. Q. Yan, T. Fujita, A. Inoue, and M. W. Chen, “Surface enhanced Raman scattering of nanoporous gold: Smaller pore sizes stronger enhancements,” Applied Physics Letters, vol. 90, no. 15, Article ID 153120, 2007.
[161]
Y. Jiao, J. D. Ryckman, P. N. Ciesielski, C. A. Escobar, G. K. Jennings, and S. M. Weiss, “Patterned nanoporous gold as an effective SERS template,” Nanotechnology, vol. 22, no. 29, Article ID 295302, 2011.
[162]
L. Zhang, X. Y. Lang, A. Hirata, and M. W. Chen, “Wrinkled nanoporous gold films with ultrahigh surface-enhanced raman scattering enhancement,” ACS Nano, vol. 5, no. 6, pp. 4407–4413, 2011.
[163]
L. H. Qian, B. Das, Y. Li, and Z. L. Yang, “Giant Raman enhancement on nanoporous gold film by conjugating with nanoparticles for single-molecule detection,” Journal of Materials Chemistry, vol. 20, no. 33, pp. 6891–6895, 2010.
[164]
Y. Deng, W. Huang, X. Chen, and Z. Li, “Facile fabrication of nanoporous gold film electrodes,” Electrochemistry Communications, vol. 10, no. 5, pp. 810–813, 2008.
[165]
G. Zhong, A. Liu, X. Chen et al., “Electrochemical biosensor based on nanoporous gold electrode for detection of PML/RARα fusion gene,” Biosensors & Bioelectronics, vol. 26, no. 9, pp. 3812–3817, 2011.
[166]
H. Qiu and X. Huang, “Effects of Pt decoration on the electrocatalytic activity of nanoporous gold electrode toward glucose and its potential application for constructing a nonenzymatic glucose sensor,” Journal of Electroanalytical Chemistry, vol. 643, no. 1-2, pp. 39–45, 2010.
[167]
L. E. Ahangar and M. A. Mehrgardi, “Nanoporous gold electrode as a platform for the construction of an electrochemical DNA hybridization biosensor,” Biosensors & Bioelectronics, vol. 38, no. 1, pp. 252–257, 2012.
[168]
G. Zhong, A. Liu, X. Xu et al., “Detection of femtomolar level osteosarcoma-related gene via a chronocoulometric DNA biosensor based on nanostructure gold electrode,” International Journal of Nanomedicine, vol. 7, pp. 527–536, 2012.
[169]
M. Zheng, P. Li, C. Yang et al., “Ferric ion immobilized on three-dimensional nanoporous gold films modified with self-assembled monolayers for electrochemical detection of hydrogen peroxide,” Analyst, vol. 137, no. 5, pp. 1182–1189, 2012.
[170]
H. Qiu, Y. Sun, X. Huang, and Y. Qu, “A sensitive nanoporous gold-based electrochemical aptasensor for thrombin detection,” Colloids and Surfaces B, vol. 79, no. 1, pp. 304–308, 2010.
[171]
S. Cherevko and C.-H. Chung, “Direct electrodeposition of nanoporous gold with controlled multimodal pore size distribution,” Electrochemistry Communications, vol. 13, no. 1, pp. 16–19, 2011.
[172]
C. Fang, N. M. Bandaru, A. V. Ellis, and N. H. Voelcker, “Electrochemical fabrication of nanoporous gold,” Journal of Materials Chemistry, vol. 22, pp. 2952–2957, 2012.
[173]
F. Jia, C. Yu, Z. Ai, and L. Zhang, “Fabrication of nanoporous gold film electrodes with ultrahigh surface area and electrochemical activity,” Chemistry of Materials, vol. 19, no. 15, pp. 3648–3653, 2007.
[174]
A. Ahmadalinezhad and A. C. Chen, “High-performance electrochemical biosensor for the detection of total cholesterol,” Biosensors & Bioelectronics, vol. 26, no. 11, pp. 4508–4513, 2011.
[175]
J. Jiang and X. Wang, “Fabrication of high-surface nanoporous gold microelectrode,” Electrochemistry Communications, vol. 20, pp. 157–159, 2012.
[176]
F. Jia, C. Yu, and L. Zhang, “Hierarchical nanoporous gold film electrode with extra high surface area and electrochemical activity,” Electrochemistry Communications, vol. 11, no. 10, pp. 1944–1946, 2009.
[177]
J. F. Huang and B. T. Lin, “Application of a nanoporous gold electrode for the sensitive detection of copper via mercury-free anodic stripping voltammetry,” Analyst, vol. 134, no. 11, pp. 2306–2313, 2009.
[178]
F. Jia, C. Yu, J. Gong, and L. Zhang, “Deposition of Prussian blue on nanoporous gold film electrode and its electrocatalytic reduction of H2O2,” Journal of Solid State Electrochemistry, vol. 12, no. 12, pp. 1567–1571, 2008.
[179]
J.-F. Huang, “Silver UPD ultra-thin film modified nanoporous gold electrode with applications in the electrochemical detection of chloride,” Talanta, vol. 77, no. 5, pp. 1694–1700, 2009.
[180]
A. Ahmadalinezhad, A. K. M. Kafi, and A. C. Chen, “Glucose biosensing based on the highly efficient immobilization of glucose oxidase on a Prussian blue modified nanostructured Au surface,” Electrochemistry Communications, vol. 11, no. 10, pp. 2048–2051, 2009.
[181]
Q. F. Yi and W. Q. Yu, “Electrocatalytic activity of a novel titanium-supported nanoporous gold catalyst for glucose oxidation,” Microchimica Acta, vol. 165, no. 3-4, pp. 381–386, 2009.
[182]
A. K. M. Kafi, A. Ahmadalinezhad, J. P. Wang, D. F. Thomas, and A. C. Chen, “Direct growth of nanoporous Au and its application in electrochemical biosensing,” Biosensors & Bioelectronics, vol. 25, no. 11, pp. 2458–2463, 2010.
