鈉離子是人體中重要的礦物質營養素，主要功用為調節滲透壓和維持體內神經，心臟，肌肉等各種生理功能正常運作。鈉的攝取主要是透過食物，特別是食鹽，但過量的攝取會導致高血壓、提高腦中風及心肌梗塞的風險。基於上述原因，我們致力於開發一種快速，可靠，靈敏度高的方法來檢測鈉離子的濃度。
在這項研究中，由於金奈米顆粒具有局部表面電漿共振的特性，於是我們利用金奈米顆粒作為此研究之感測器。根據局部表面電漿共振效應的原理，此感測器可以透過肉眼觀察到之顏色差異來得知鈉鹽濃度的變化。這種現象可歸因於加入鈉離子導致金奈米顆粒團聚，而團聚則造成金奈米顆粒在顏色上產生改變。此外，為了提高其感測之靈敏度，我們利用抗壞血酸進一步修飾金奈米顆粒的表面，有效地減少顏色變化的反應時間。另外，為了得知未知樣品中鈉離子的濃度，我們利用紫外光/可見光光譜分度計測量了各濃度的最大吸光度建立一多項式迴歸圖做為定量分析之使用，此多項式迴歸圖可用A=0.73545+0.00206c-0.00854t-0.00033ct-9.9E-5c^2+0.00033t^2 此式子來描述。由於此式之決定係數高達0.9581，因此，此方法用來測量未知濃度之鈉離子及預測最大吸光度是非常可靠及精確的。在本研究中，我們還測試了在不同環境下對於金奈米顆粒的影響，發現溶液的酸鹼、溫度及離子強度會顯著的影響金奈米顆粒的團聚。而根據阿瑞尼士方程式，我們推斷經修飾過金奈米顆粒團聚的活化能約為22.5 kJ mol-1。最後，我們還研究了金奈米顆粒的重複利用性及專一性以及嘗試利用銅奈米顆粒進行感測。
期許這種簡單的肉眼顏色辨識之檢測結合定量分析之方法及上述的研究在未來能廣泛運用於生物和化學感測領域。

Sodium ions are necessary for regulating osmotic pressure and assisting the operation of nerve, heart, muscle and various physiological functions in the body. Sodium intake is mainly through food, especially salt. However, excessive sodium intake is harmful because it may lead to the high risk of heart attack, stroke and the development of cardiovascular disease. For the above-mentioned reasons, we worked on developing a rapid, reliable, and sensitive method to detect salt concentration which can be directly monitored by naked eyes.
In this study, we utilize the gold nanoparticles (AuNPs) as the colorimetric sensor due to the remarkable characteristic of localized surface plasmon resonance (LSPR) at visible wavelength regions. Based on the concept of LSPR effect, the designed AuNP-based sensor can readily monitor the change of salt concentrations through the color change observed by naked eyes. This phenomenon can be attributed to the ion-induced aggregation of AuNPs, where the response time relative to the salt concentrations can be modulated with the proper control of related detection conditions. Furthermore, in order to improve their detection sensitivity, the ascorbic acid was utilized to further modify the surfaces of AuNPs, and can efficiently reduce the reaction time for showing color change. Moreover, for the purpose of determining the concentration of sodium ions in an unknown sample, we measured the maximum absorbance of various concentrations and represented as a calibration curve for quantitation analysis. A calibration curve based on polynomial regression analysis is a reliable approach due to the high coefficient of determination. Using the equation (A=0.73545+0.00206c-0.00854t-0.00033ct-9.9E-5c^2+0.00033t^2) is practical for real experimental data and it also can be utilized to predict the corresponding absorbance. Environmental influences are investigated in our study. The aggregation of modified gold nanoparticles is found to depend on pH, ionic strength and temperature significantly. Moreover, we infer that the activation energy of the aggregation from modified gold nanoparticles is approximately 22.5 kJ mol-1 according to Arrhenius equation. In the end, we have conducted the experiments on repetitive utilization and specificity of gold nanoparticles and investigated the sensing capability of copper nanoparticles.
Therefore, such visual detection of sodium ions combining the precise quantitation analysis and detailed investigations aforementioned are expected for apply in biological and chemical sensing areas in the future.

[1] H. C. Hemmings and T. D. Egan, Pharmacology and physiology for anesthesia: foundations and clinical application. Elsevier Health Sciences, 2013.
[2] M. Blaustein, "Sodium ions, calcium ions, blood pressure regulation, and hypertension: a reassessment and a hypothesis," American Journal of Physiology-Cell Physiology, vol. 232, no. 5, pp. C165-C173, 1977.
[3] Q. Ye, Q. Li, Q. Lv, Y. Li, and Y. Gong, "Determination methods of sodium ion in food," Journal of Food Safety and Quality, vol. 7, no. 11, pp. 4576-4580, 2016.
[4] V. Pareek, A. Bhargava, R. Gupta, N. Jain, and J. Panwar, "Synthesis and applications of noble metal nanoparticles: a review," Advanced Science, Engineering and Medicine, vol. 9, no. 7, pp. 527-544, 2017.
[5] I. Khan, K. Saeed, and I. Khan, "Nanoparticles: Properties, applications and toxicities," Arabian Journal of Chemistry, 2017.
[6] V. Pokropivny, R. Lohmus, I. Hussainova, A. Pokropivny, and S. Vlassov, Introduction to nanomaterials and nanotechnology. Tartu University Press Tartu, Estonia, 2007.
[7] F. E. Kruis, H. Fissan, and A. Peled, "Synthesis of nanoparticles in the gas phase for electronic, optical and magnetic applications—a review," Journal of aerosol science, vol. 29, no. 5-6, pp. 511-535, 1998.
[8] E. Priyadarshini and N. Pradhan, "Gold nanoparticles as efficient sensors in colorimetric detection of toxic metal ions: A review," Sensors and Actuators B: Chemical, vol. 238, pp. 888-902, 2017.
[9] V. K. Upadhyayula, "Functionalized gold nanoparticle supported sensory mechanisms applied in detection of chemical and biological threat agents: a review," Analytica Chimica Acta, vol. 715, pp. 1-18, 2012.
[10] Y. Wu, S. Zhan, F. Wang, L. He, W. Zhi, and P. Zhou, "Cationic polymers and aptamers mediated aggregation of gold nanoparticles for the colorimetric detection of arsenic (III) in aqueous solution," Chemical communications, vol. 48, no. 37, pp. 4459-4461, 2012.
[11] Y. Guo, Z. Wang, W. Qu, H. Shao, and X. Jiang, "Colorimetric detection of mercury, lead and copper ions simultaneously using protein-functionalized gold nanoparticles," Biosensors and Bioelectronics, vol. 26, no. 10, pp. 4064-4069, 2011.
[12] P. Zhao, N. Li, and D. Astruc, "State of the art in gold nanoparticle synthesis," Coordination Chemistry Reviews, vol. 257, no. 3-4, pp. 638-665, 2013.
[13] J. Polte, "Fundamental growth principles of colloidal metal nanoparticles–a new perspective," CrystEngComm, vol. 17, no. 36, pp. 6809-6830, 2015.
[14] V. Amendola and M. Meneghetti, "Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles," Physical chemistry chemical physics, vol. 11, no. 20, pp. 3805-3821, 2009.
[15] A. V. Kabashin and M. Meunier, "Synthesis of colloidal nanoparticles during femtosecond laser ablation of gold in water," Journal of Applied Physics, vol. 94, no. 12, pp. 7941-7943, 2003.
[16] F. Mafuné, J.-y. Kohno, Y. Takeda, and T. Kondow, "Full physical preparation of size-selected gold nanoparticles in solution: laser ablation and laser-induced size control," The Journal of Physical Chemistry B, vol. 106, no. 31, pp. 7575-7577, 2002.
[17] F. Mafuné, J.-y. Kohno, Y. Takeda, T. Kondow, and H. Sawabe, "Formation of gold nanoparticles by laser ablation in aqueous solution of surfactant," The Journal of Physical Chemistry B, vol. 105, no. 22, pp. 5114-5120, 2001.
[18] J.-P. Sylvestre, A. V. Kabashin, E. Sacher, M. Meunier, and J. H. Luong, "Stabilization and size control of gold nanoparticles during laser ablation in aqueous cyclodextrins," Journal of the American Chemical Society, vol. 126, no. 23, pp. 7176-7177, 2004.
[19] X. Xu et al., "Fabrication of gold nanoparticles by laser ablation in liquid and their application for simultaneous electrochemical detection of Cd2+, Pb2+, Cu2+, Hg2+," ACS applied materials & interfaces, vol. 6, no. 1, pp. 65-71, 2013.
[20] M. T. Swihart, "Vapor-phase synthesis of nanoparticles," Current Opinion in Colloid & Interface Science, vol. 8, no. 1, pp. 127-133, 2003.
[21] J. Turkevich, P. C. Stevenson, and J. Hillier, "A study of the nucleation and growth processes in the synthesis of colloidal gold," Discussions of the Faraday Society, vol. 11, pp. 55-75, 1951.
[22] J. Kimling, M. Maier, B. Okenve, V. Kotaidis, H. Ballot, and A. Plech, "Turkevich method for gold nanoparticle synthesis revisited," The Journal of Physical Chemistry B, vol. 110, no. 32, pp. 15700-15707, 2006.
[23] N. R. Jana, L. Gearheart, and C. J. Murphy, "Seed‐mediated growth approach for shape‐controlled synthesis of spheroidal and rod‐like gold nanoparticles using a surfactant template," Advanced Materials, vol. 13, no. 18, pp. 1389-1393, 2001.
[24] M.-C. Daniel and D. Astruc, "Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology," Chemical reviews, vol. 104, no. 1, pp. 293-346, 2004.
[25] M. Grzelczak, J. Pérez-Juste, P. Mulvaney, and L. M. Liz-Marzán, "Shape control in gold nanoparticle synthesis," Chemical Society Reviews, vol. 37, no. 9, pp. 1783-1791, 2008.
[26] W. Leng, P. Pati, and P. J. Vikesland, "Room temperature seed mediated growth of gold nanoparticles: mechanistic investigations and life cycle assesment," Environmental Science: Nano, vol. 2, no. 5, pp. 440-453, 2015.
[27] B. Sepúlveda, P. C. Angelomé, L. M. Lechuga, and L. M. Liz-Marzán, "LSPR-based nanobiosensors," nano today, vol. 4, no. 3, pp. 244-251, 2009.
[28] E. Hutter and J. H. Fendler, "Exploitation of localized surface plasmon resonance," Advanced materials, vol. 16, no. 19, pp. 1685-1706, 2004.
[29] K. M. Mayer and J. H. Hafner, "Localized Surface Plasmon Resonance Sensors," Chemical Reviews, vol. 111, no. 6, pp. 3828-3857, 2011/06/08 2011.
[30] E. Petryayeva and U. J. Krull, "Localized surface plasmon resonance: nanostructures, bioassays and biosensing—a review," Analytica chimica acta, vol. 706, no. 1, pp. 8-24, 2011.
[31] 曾賢德, "金奈米粒子的表面電漿共振特性: 耦合, 應用與樣品製作," 物理雙 月刊, pp. 32,126-135, 2010.
[32] K. A. Willets and R. P. Van Duyne, "Localized surface plasmon resonance spectroscopy and sensing," Annu. Rev. Phys. Chem., vol. 58, pp. 267-297, 2007.
[33] S. Link and M. A. El-Sayed, "Size and temperature dependence of the plasmon absorption of colloidal gold nanoparticles," The Journal of Physical Chemistry B, vol. 103, no. 21, pp. 4212-4217, 1999.
[34] J. N. Israelachvili, Intermolecular and surface forces. Academic press, 2011.
[35] P. Attard, "Electrolytes and the electric double layer," Advances in Chemical Physics, vol. 92, pp. 1-160, 1996.
[36] P. Attard, "Recent advances in the electric double layer in colloid science," Current Opinion in Colloid & Interface Science, vol. 6, no. 4, pp. 366-371, 2001.
[37] J. Zhou, J. Ralston, R. Sedev, and D. A. Beattie, "Functionalized gold nanoparticles: synthesis, structure and colloid stability," Journal of colloid and interface science, vol. 331, no. 2, pp. 251-262, 2009.
[38] S.-J. Park and M.-K. Seo, "Intermolecular Force," in Interface Science and Technology, vol. 18: Elsevier, 2011, pp. 1-57.
[39] J. Adair, E. Suvaci, and J. Sindel, "Surface and colloid chemistry," 2001.
[40] A. M. El Badawy, T. P. Luxton, R. G. Silva, K. G. Scheckel, M. T. Suidan, and T. M. Tolaymat, "Impact of Environmental Conditions (pH, Ionic Strength, and Electrolyte Type) on the Surface Charge and Aggregation of Silver Nanoparticles Suspensions," (in English), Environmental Science & Technology, Article vol. 44, no. 4, pp. 1260-1266, Feb 2010.
[41] Y. Ju-Nam and J. R. Lead, "Manufactured nanoparticles: an overview of their chemistry, interactions and potential environmental implications," Science of the total environment, vol. 400, no. 1-3, pp. 396-414, 2008.
[42] K. Kim, Y.-S. Nam, Y. Lee, and K.-B. Lee, "Highly Sensitive Colorimetric Assay for Determining Fe3+ Based on Gold Nanoparticles Conjugated with Glycol Chitosan," Journal of Analytical Methods in Chemistry, vol. 2017, p. 11, 2017, Art. no. 3648564.
[43] T. M. D. Dang, T. T. T. Le, E. Fribourg-Blanc, and M. C. Dang, "Synthesis and optical properties of copper nanoparticles prepared by a chemical reduction method," Advances in Natural Sciences: Nanoscience and Nanotechnology, vol. 2, no. 1, p. 015009, 2011.
[44] S. Kumar, K. Gandhi, and R. Kumar, "Modeling of formation of gold nanoparticles by citrate method," Industrial & Engineering Chemistry Research, vol. 46, no. 10, pp. 3128-3136, 2007.
[45] J. r. Polte et al., "Mechanism of gold nanoparticle formation in the classical citrate synthesis method derived from coupled in situ XANES and SAXS evaluation," Journal of the American Chemical Society, vol. 132, no. 4, pp. 1296-1301, 2010.
[46] 陳廷臻, "建構高靈敏金奈米顆粒於鈉鹽之檢測與仿生性的超疏水高親油性的複合海綿之研究," 暨南大學應用材料及光電工程學系學位論文, pp. 1-50, 2017.
[47] C. Burns, W. U. Spendel, S. Puckett, and G. E. Pacey, "Solution ionic strength effect on gold nanoparticle solution color transition," (in English), Talanta, Article vol. 69, no. 4, pp. 873-876, Jun 2006.
[48] J. Zhang, Y. Wang, X. W. Xu, and X. R. Yang, "Specifically colorimetric recognition of calcium, strontium, and barium ions using 2-mercaptosuccinic acid-functionalized gold nanoparticles and its use in reliable detection of calcium ion in water," (in English), Analyst, Article vol. 136, no. 19, pp. 3865-3868, 2011.
[49] A. Dutta, A. Paul, and A. Chattopadhyay, "The effect of temperature on the aggregation kinetics of partially bare gold nanoparticles," RSC Advances, vol. 6, no. 85, pp. 82138-82149, 2016.