{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,23]],"date-time":"2026-01-23T08:16:10Z","timestamp":1769156170783,"version":"3.49.0"},"reference-count":33,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2020,9,11]],"date-time":"2020-09-11T00:00:00Z","timestamp":1599782400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004663","name":"Ministry of Science and Technology, Taiwan","doi-asserted-by":"publisher","award":["MOST-106-2221-E-006-173-MY3, MOST-105-2221-E-006-057-MY3 and MOST-108-2119-M-010-001-"],"award-info":[{"award-number":["MOST-106-2221-E-006-173-MY3, MOST-105-2221-E-006-057-MY3 and MOST-108-2119-M-010-001-"]}],"id":[{"id":"10.13039\/501100004663","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>Adenine is an important molecule for biomedical and agricultural research and applications. The detection of low concentration adenine molecules is thus desirable. Surface-enhanced Raman scattering (SERS) is a promising label-free detection and fingerprinting technique for molecules of significance. A novel SERS sensor made of clusters of silver nanostructures deposited on copper bumps in valleys of an etched silicon substrate was previously reported to exhibit a low and reproducible detection limit for a 10\u221211 M neutral adenine aqueous solution. Reflection of laser illumination from the silicon surface surrounding a valley provides additional directions of laser excitation to adenine molecules adsorbing on a silver surface for the generation of enhanced SERS signal strength leading to a low detection limit. This paper further reports a concentration dependent shift of the ring-breathing mode SERS adenine peak towards 760 cm\u22121 with decreasing concentration and its pH-dependent SERS signal strength. For applications, where the pH value can vary, reproducible detection of 10\u221212 M adenine in a pH 9 aqueous solution is feasible, making the novel SERS structure a desirable pico-molar adenine sensor.<\/jats:p>","DOI":"10.3390\/bios10090122","type":"journal-article","created":{"date-parts":[[2020,9,11]],"date-time":"2020-09-11T09:05:16Z","timestamp":1599815116000},"page":"122","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Silver-Based SERS Pico-Molar Adenine Sensor"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4763-1144","authenticated-orcid":false,"given":"Yonhua","family":"Tzeng","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, National Cheng Kung University, Tainan 701401, Taiwan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bo-Yi","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Cheng Kung University, Tainan 701401, Taiwan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/j.cplett.2010.01.062","article-title":"Plasmonic coupling in noble metal nanostructures","volume":"487","author":"Jain","year":"2010","journal-title":"Chem. Phys. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"7138","DOI":"10.1039\/C7NR06656B","article-title":"Tuning plasmons layer-by-layer for quantitative colloidal sensing with surface-enhanced Raman spectroscopy","volume":"10","author":"Anderson","year":"2018","journal-title":"Nanoscale"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1002\/cphc.201701223","article-title":"The controlversial orientation of adenine on gold and silver","volume":"19","author":"Harroun","year":"2018","journal-title":"ChemPhysChem"},{"key":"ref_4","first-page":"2645","article-title":"Adenine and RNA in mineral samples. Surface-enhanced Raman spectroscopy (SERS) for picomole detections","volume":"59","author":"Baron","year":"2003","journal-title":"Spectrochim. Acta Part A"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"175610-14","DOI":"10.1088\/0957-4484\/18\/17\/175610","article-title":"Silver nanoparticles coated with adenine: Preparation, self-assembly and application in surface-enhanced Raman scattering","volume":"18","author":"Wei","year":"2007","journal-title":"Nanotechnology"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.saa.2012.09.079","article-title":"SERS study on adenine using a Ag\/poly(t-butylacrylate) nanocomposite","volume":"101","author":"Pinheiro","year":"2013","journal-title":"Spectrochim. Acta Part A Mol. Biomol. Spectrosc."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"21072","DOI":"10.1039\/C4CP04946B","article-title":"Prospects for plasmonic hot spots in single molecule SERS towards the chemical imaging of live cells","volume":"17","author":"Radziuk","year":"2015","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1109\/TNANO.2019.2954490","article-title":"Silver nanoparticles SERS sensors using rapid thermal CVD nanoscale graphene islands as templates","volume":"19","author":"Tzeng","year":"2020","journal-title":"IEEE Trans. Nanotechnol."},{"key":"ref_9","unstructured":"Tzeng, Y., and Chen, Y.-R. (2019). Carrier for Raman Spectroscopy and Method of Manufacturing the Same. (10,429,308), U.S. Patent."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Tzeng, Y., and Lin, B.-Y. (2020). Silver SERS adenine sensors with a very low detection limit. Biosensors, 10.","DOI":"10.3390\/bios10050053"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1021\/jp010789f","article-title":"Surface-enhanced raman spectroscopic and density functional theory study of adenine adsorption to silver surfaces","volume":"106","author":"Giese","year":"2002","journal-title":"J. Phys. Chem. B"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1209","DOI":"10.1016\/S1386-1425(98)00283-2","article-title":"Comparative study of the surface enhanced near infrared Raman spectra of adenine and NAD+ on a gold electrode","volume":"55","author":"Xiao","year":"1999","journal-title":"Spectrochim. Acta Part A Mol. Biomol. Spectrosc."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Mirajkar, S., Dhayagude, A., Maiti, N., Suprasanna, P., and Kapoor, S. (2019). Distinguishing genomic DNA of brassica juncea and arabidopsis thaliana using surface-enhanced raman scattering. J. Raman Spectrsc.","DOI":"10.1002\/jrs.5758"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"9014","DOI":"10.1021\/ja035756n","article-title":"Base-dependent competitive adsorption of single-stranded DNA on gold","volume":"125","author":"Petrovykh","year":"2003","journal-title":"J. Am. Chem. Soc."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1016\/j.diamond.2012.01.005","article-title":"Surface-enhanced raman spectroscopy for characterization of nanodiamond seeded substrates and ultrananocrystalline diamond at the early-stage of plasma cvd growth process","volume":"24","author":"Chen","year":"2012","journal-title":"Diamond Relat. Mater."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"17092","DOI":"10.1364\/OE.19.017092","article-title":"Plasmonic coupling of silver nanoparticles covered by hydrogen-terminated graphene for surface-enhanced Raman spectroscopy","volume":"19","author":"Liu","year":"2011","journal-title":"Opt. Express"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"11441","DOI":"10.1364\/OE.19.011441","article-title":"Electrochemically fabricated self-aligned 2-D silver\/alumina arrays as reliable SERS sensors","volume":"19","author":"Huang","year":"2011","journal-title":"Opt. Express"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"27891","DOI":"10.1364\/OE.18.027891","article-title":"Plasmon-induced optical switching of electrical conductivity in porous anodic aluminum oxide films encapsulated with silver nanoparticle arrays","volume":"18","author":"Huang","year":"2010","journal-title":"Opt. Express"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1007\/s10404-019-2216-z","article-title":"A particle-based microfluidic molecular separation integrating surface-enhanced Raman scattering sensing for purine derivatives analysis","volume":"23","author":"Wang","year":"2019","journal-title":"Microfluid Nanofluid"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"117380","DOI":"10.1016\/j.saa.2019.117380","article-title":"Colloidal gold clusters formation and chemometrics for direct SERS determination of bioanalytes in complex media","volume":"224","author":"Villa","year":"2020","journal-title":"Spectrochim. Acta Part A Mol. Biomol. Spectrosc."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Lee, Y.-C., and Chiu, C.-W. (2019). Immobilization and 3D hot-junction formation of gold nanoparticles on two-dimensional silicate nanoplatelets as substrates for high-efficiency surface-enhanced raman scattering detection. Nanomaterials, 9.","DOI":"10.3390\/nano9030324"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"111596","DOI":"10.1016\/j.bios.2019.111596","article-title":"Plasmonic-3D photonic crystals microchip for surface enhanced Raman spectroscopy","volume":"143","author":"Chen","year":"2019","journal-title":"Biosens. Bioelectron."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.snb.2017.11.058","article-title":"A silver-grafted sponge as an effective surface-enhanced Raman scattering substrate","volume":"258","author":"Zhou","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.colsurfa.2019.05.042","article-title":"Cheung, Liu, T-Y. Floating SERS substrates of silver nanoparticles-graphene based nanosheets for rapid detection of biomolecules and clinical uremic toxins","volume":"576","author":"Juang","year":"2019","journal-title":"Colloids Surf. A Physicochem. Eng. Asp."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Ikegami, K., Sugano, K., and Isono, Y. (2017, January 22\u201326). Surface-enhanced raman spectroscopy analysis of DNA bases using arrayed and single dimer of gold nanoparticle. Proceedings of the IEEE MEMS 2017, Las Vegas, NV, USA.","DOI":"10.1109\/MEMSYS.2017.7863428"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2044","DOI":"10.1021\/jp4105757","article-title":"Etching silicon with HF-H2O2-based mixtures: Reactivity studies and surface investigations","volume":"118","author":"Gondek","year":"2014","journal-title":"J. Phys. Chem. C"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"095003","DOI":"10.1088\/2053-1591\/ab2a36","article-title":"Introduction of copper ions to regulate silver nanostructures by galvanic displacement reaction","volume":"6","author":"Yang","year":"2019","journal-title":"Mater. Res. Express"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Laptinskiy, K.A., Burikov, S.A., and Dolenko, T.A. (2015, January 19). Determination of type and concentration of DNA nitrogenous bases by Raman spectroscopy. Proceedings of the Saratov Fall Meeting 2014: Optical Technologies in Biophysics and Medicine XVI, Laser Physics and Photonics XVI, and Computational Biophysics, Saratov, Russia.","DOI":"10.1117\/12.2180055"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"14611","DOI":"10.1039\/c3cp52564c","article-title":"Direct conversion of silver complexes to nanoscale hexagonal columns on a copper alloy for plasmonic applications","volume":"15","author":"Yamamoto","year":"2013","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"22644","DOI":"10.1021\/jp1092256","article-title":"Structure of adenine on metal nanoparticles: PH equilibria and formation of Ag+ complexes detected by surface-enhanced Raman spectroscopy","volume":"114","author":"Papadopoulou","year":"2010","journal-title":"J. Phys. Chem. C"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"155418","DOI":"10.1103\/PhysRevB.69.155418","article-title":"Tip-enhanced near-field Raman analysis of tip-pressurized adenine molecule","volume":"69","author":"Watanabe","year":"2004","journal-title":"Phys. Rev. B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1002\/jrs.5272","article-title":"Adsorption orientationof 8-azaadenine on silver nanoparticles determined by SERS and DFT","volume":"49","author":"Harroun","year":"2018","journal-title":"J. Raman Spectrosc."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1016\/S0006-3495(01)76027-4","article-title":"Fourier transform raman study of the structural specificities on the interaction between DNA and biogenic polyamines","volume":"80","author":"Medina","year":"2001","journal-title":"Biophys. J."}],"container-title":["Biosensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-6374\/10\/9\/122\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:08:57Z","timestamp":1760177337000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-6374\/10\/9\/122"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,9,11]]},"references-count":33,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2020,9]]}},"alternative-id":["bios10090122"],"URL":"https:\/\/doi.org\/10.3390\/bios10090122","relation":{},"ISSN":["2079-6374"],"issn-type":[{"value":"2079-6374","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,9,11]]}}}