{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,16]],"date-time":"2026-06-16T12:49:27Z","timestamp":1781614167945,"version":"3.54.5"},"reference-count":41,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2019,6,15]],"date-time":"2019-06-15T00:00:00Z","timestamp":1560556800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Italian \u201cMinistero dell\u2019Istruzione, dell\u2019Universita\u0300 e della Ricerca\u201d (MIUR)","award":["Grant RBFR1248UI_002"],"award-info":[{"award-number":["Grant RBFR1248UI_002"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>We have studied the adsorption of xanthine, a nucleobase present in human tissue and fluids that is involved in important metabolic processes, on citrate-reduced gold colloidal nanoparticles by means of surface-enhanced Raman scattering (SERS), absorption, and X-ray photoelectron spectroscopy (XPS) measurements, along with density functional theory (DFT) calculations. The citrate anions stabilize the colloidal suspensions by strongly binding the gold nanoparticles. However, these anions do not impair the adsorption of xanthine on positively-charged active sites present on the metal surface. We have obtained the Fourier transform (FT)-SERS spectra of adsorbed xanthine by laser excitation in the near infrared spectral region, where interference due to fluorescence emission does not usually occur. In fact, the addition of chloride ions to the Au\/xanthine colloid induces the aggregation of the gold nanoparticles, whose plasmonic band is shifted to the near infrared region where there is the exciting laser line of the FT\u2013Raman instrument. Hence, this analytical approach is potentially suitable for spectroscopic determination of xanthine directly in body fluids, avoiding fluorescence phenomena induced by visible laser irradiation.<\/jats:p>","DOI":"10.3390\/s19122700","type":"journal-article","created":{"date-parts":[[2019,6,17]],"date-time":"2019-06-17T03:24:41Z","timestamp":1560741881000},"page":"2700","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":52,"title":["SERS, XPS and DFT Study of Xanthine Adsorbed on Citrate-Stabilized Gold Nanoparticles"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5673-0462","authenticated-orcid":false,"given":"Stefano","family":"Caporali","sequence":"first","affiliation":[{"name":"Department of Industrial Engineering, University of Florence, Via S. Marta 3, 50139 Firenze, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7614-2326","authenticated-orcid":false,"given":"Francesco","family":"Muniz-Miranda","sequence":"additional","affiliation":[{"name":"Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3772-7222","authenticated-orcid":false,"given":"Alfonso","family":"Pedone","sequence":"additional","affiliation":[{"name":"Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9457-6833","authenticated-orcid":false,"given":"Maurizio","family":"Muniz-Miranda","sequence":"additional","affiliation":[{"name":"Department of Chemistry \u201cUgo Schiff\u201d, University of Florence, Via Lastruccia 3, 50019 Sesto Fiorentino, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,6,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2740","DOI":"10.1039\/C1CS15237H","article-title":"The golden age: Gold nanoparticles for biomedicine","volume":"41","author":"Dreaden","year":"2012","journal-title":"Chem. Soc. Rev."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"537","DOI":"10.1016\/j.talanta.2018.02.088","article-title":"Recent biomedical applications of gold nanoparticles: A review","volume":"184","author":"Elahi","year":"2018","journal-title":"Talanta"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"203002","DOI":"10.1088\/1361-648X\/aa60f3","article-title":"Surface plasmon resonance in gold nanoparticles: A review","volume":"29","author":"Amendola","year":"2017","journal-title":"J. Phys. Condens. Matter"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1869","DOI":"10.1166\/jnn.2015.9718","article-title":"Functionalized Gold Nanoparticles: Synthesis, Properties and Applications\u2014A Review","volume":"15","author":"Alex","year":"2015","journal-title":"J. Nanosci. Nanotechnol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Kong, F.-Y., Zhang, J.-W., Li, R.-F., Wang, Z.-X., Wang, W.-J., and Wang, W. (2017). Unique Roles of Gold Nanoparticles in Drug Delivery, Targeting and Imaging Applications. Molecules, 22.","DOI":"10.3390\/molecules22091445"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"14388","DOI":"10.1039\/C4NR04400B","article-title":"Plasmonic caged gold nanorods for near-infrared light controlled drug delivery","volume":"6","author":"Xiong","year":"2014","journal-title":"Nanoscale"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"288","DOI":"10.1016\/j.jcis.2008.02.015","article-title":"Interaction of DNA bases with silver nanoparticles: Assembly quantified through SPRS and SERS","volume":"321","author":"Basu","year":"2008","journal-title":"J. Colloid Interface Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2943","DOI":"10.1038\/s41598-018-20229-z","article-title":"Ultrasensitive optical biosensor for detection of miRNA-155 using positively charged Au nanoparticles","volume":"8","author":"Hakimian","year":"2018","journal-title":"Sci. Rep."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"22121","DOI":"10.1039\/C7CP03692B","article-title":"Quantification of nucleobases\/gold nanoparticles interactions: Energetics of the interactions through apparent binding constants determination","volume":"19","author":"Carnerero","year":"2017","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1039\/df9511100055","article-title":"A Study of the nucleation and growth processes in the synthesis of colloidal gold","volume":"11","author":"Turkevich","year":"1951","journal-title":"Discuss. Faraday Soc."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1038\/physci241020a0","article-title":"Controlled Nucleation for the Regulation of the Particle Size in Monodisperse Gold Suspensions","volume":"241","author":"Frens","year":"1973","journal-title":"Nat. Phys. Sci. (London)"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3128","DOI":"10.1021\/ie060672j","article-title":"Modeling of Formation of Gold Nanoparticles by Citrate Method","volume":"46","author":"Kumar","year":"2007","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"13939","DOI":"10.1021\/ja074447k","article-title":"Size Control of Gold Nanocrystals in Citrate Reduction:\u2009 The Third Role of Citrate","volume":"129","author":"Ji","year":"2007","journal-title":"J. Am. Chem. Soc."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1006\/jcht.2000.0723","article-title":"Solubility and dissolution enthalpy of xanthine","volume":"33","author":"Wang","year":"2001","journal-title":"J. Chem. Thermodyn."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2391","DOI":"10.1172\/JCI119421","article-title":"Identification of two mutations in human xanthine dehydrogenase gene responsible for classical type I xanthinuria","volume":"99","author":"Ichida","year":"1997","journal-title":"J. Clin. Investig."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Schl\u00fccker, S. (2011). Surface Enhanced Raman Spectroscopy: Analytical, Biophysical and Life Science Applications, Wiley-VCH.","DOI":"10.1002\/9783527632756"},{"key":"ref_17","unstructured":"Proch\u00e1zka, M. (2016). Surface-Enhanced Raman Spectroscopy, Bioanalytical, Biomolecular and Medical Applications, Springer."},{"key":"ref_18","unstructured":"Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Scalmani, G., Barone, V., Mennucci, B., and Petersson, G.A. (2009). Gaussian 09, Gaussian, Inc.. Revision D.01."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"5648","DOI":"10.1063\/1.464913","article-title":"Density-functional thermochemistry III. The role of exact exchange","volume":"98","author":"Becke","year":"1993","journal-title":"J. Chem. Phys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"785","DOI":"10.1103\/PhysRevB.37.785","article-title":"Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density","volume":"37","author":"Lee","year":"1988","journal-title":"Phys. Rev. B"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"270","DOI":"10.1063\/1.448799","article-title":"Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg","volume":"82","author":"Hay","year":"1985","journal-title":"J. Chem. Phys."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"284","DOI":"10.1063\/1.448800","article-title":"Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi","volume":"82","author":"Wadt","year":"1985","journal-title":"J. Chem. Phys."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1063\/1.448975","article-title":"Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals","volume":"82","author":"Hay","year":"1985","journal-title":"J. Chem. Phys."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2007","DOI":"10.1016\/S0584-8539(09)91012-1","article-title":"Vibrational spectra of monothiocarbamates-II. IR and Raman spectra, vibrational assignment, conformational analysis and ab initio calculations of S-methyl-N,N-dimethylthiocarbamate","volume":"49","author":"Keresztury","year":"1993","journal-title":"Spectrochim. Acta A"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Chalmers, J.M., and Griffiths, P.R. (2002). Handbook of Vibrational Spectroscopy, Wiley & Sons.","DOI":"10.1002\/0470027320"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"6253","DOI":"10.1016\/j.tsf.2007.11.118","article-title":"Anodic behaviour of tin in citrate solutions: The IR and XPS study on the composition of the passive layer","volume":"516","author":"Tselesh","year":"2008","journal-title":"Thin Solid Films"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1665","DOI":"10.1021\/nn506379m","article-title":"Strong Resistance of Citrate Anions on Metal Nanoparticles to Desorption under Thiol Functionalization","volume":"9","author":"Park","year":"2015","journal-title":"ACS Nano"},{"key":"ref_28","unstructured":"Wagner, C.D., Riggs, W.M., Davis, L.E., Moulder, J.F., and Muilenberg, G.E. (1979). Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corporation."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"72","DOI":"10.14202\/vetworld.2014.72-77","article-title":"Gold nanoparticle: Synthesis and characterization","volume":"7","author":"Verma","year":"2014","journal-title":"Vet. World"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1016\/j.cap.2009.09.005","article-title":"Facile strategy for stability control of gold nanoparticles synthesized by aqueous reduction method","volume":"10","author":"Muangnapoh","year":"2010","journal-title":"Curr. Appl. Phys."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.saa.2013.12.035","article-title":"Investigation of solvent polarity effect on molecular structure and vibrational spectrum of xanthine with the aid of quantum chemical computations","volume":"123","author":"Polat","year":"2014","journal-title":"Spectrochim. Acta Part A"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"493","DOI":"10.18388\/abp.2004_3587","article-title":"Xanthine, xanthosine and its nucleotides: Solution structures of neutral and ionic forms, and relevance to substrate properties in various enzyme systems and metabolic pathways","volume":"51","author":"Kulikowska","year":"2004","journal-title":"Acta Biochim. Pol."},{"key":"ref_33","first-page":"39","article-title":"Competitive Solvation and Chemisorption in Silver Colloidal Suspensions","volume":"139","author":"Pagliai","year":"2011","journal-title":"Progr. Colloid Polym. Sci."},{"key":"ref_34","first-page":"S357","article-title":"SERS effect from Pd surfaces coated with thin films of Ag colloidal nanoparticles","volume":"615","author":"Pergolese","year":"2015","journal-title":"J. Alloys Compd."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"3597","DOI":"10.1021\/acs.jpcc.6b11628","article-title":"Magneto-plasmonic colloidal nanoparticles obtained by laser ablation of nickel and silver targets in water","volume":"121","author":"Gellini","year":"2017","journal-title":"J. Phys. Chem. C"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"14390","DOI":"10.1021\/jp903126f","article-title":"Adenine- and Adenosine Monophosphate (AMP)-Gold Binding Interactions Studied by Surface-Enhanced Raman and Infrared Spectroscopies","volume":"113","author":"Kundu","year":"2009","journal-title":"J. Phys. Chem. C"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"242","DOI":"10.1021\/jz201526v","article-title":"SERS, XPS, and DFT Study of Adenine Adsorption on Silver and Gold Surfaces","volume":"3","author":"Pagliai","year":"2012","journal-title":"J. Phys. Chem. Lett."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"3610","DOI":"10.1039\/b508850j","article-title":"SERS studies of the adsorption of guanine derivatives on gold colloidal nanoparticles","volume":"7","author":"Pergolese","year":"2005","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"13530","DOI":"10.1021\/acsomega.8b02174","article-title":"Raman and Computational Study on the Adsorption of Xanthine on Silver Nanocolloids","volume":"3","author":"Pedone","year":"2018","journal-title":"ACS Omega"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"7485","DOI":"10.1021\/ja00284a007","article-title":"Fourier transform Raman spectroscopy","volume":"108","author":"Chase","year":"1986","journal-title":"J. Am. Chem. Soc."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"710","DOI":"10.1038\/nnano.2009.326","article-title":"Bioimaging: Second window for in vivo imaging","volume":"4","author":"Smith","year":"2009","journal-title":"Nat. Nanotechnol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/12\/2700\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:58:46Z","timestamp":1760187526000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/12\/2700"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,6,15]]},"references-count":41,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2019,6]]}},"alternative-id":["s19122700"],"URL":"https:\/\/doi.org\/10.3390\/s19122700","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,6,15]]}}}