{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T19:46:14Z","timestamp":1792784774962,"version":"4.5.0"},"reference-count":33,"publisher":"American Chemical Society (ACS)","issue":"39","license":[{"start":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T00:00:00Z","timestamp":1790294400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100031306","name":"Bundesministerium f??r Arbeit und Wirtschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100031306","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004612","name":"Funda????o Arauc??ria","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004612","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004955","name":"??sterreichische Forschungsf??rderungsgesellschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004955","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003593","name":"Conselho Nacional de Desenvolvimento Cient??fico e Tecnol??gico","doi-asserted-by":"publisher","award":["305333\/2023-2"],"award-info":[{"award-number":["305333\/2023-2"]}],"id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006012","name":"Christian Doppler Forschungsgesellschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100006012","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100010132","name":"??sterreichische Nationalstiftung f??r Forschung, Technologie und Entwicklung","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100010132","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002322","name":"Coordena????o de Aperfei??oamento de Pessoal de N??vel Superior","doi-asserted-by":"publisher","award":["001"],"award-info":[{"award-number":["001"]}],"id":[{"id":"10.13039\/501100002322","id-type":"DOI","asserted-by":"publisher"}]},{"name":"TU WIen Bibliothek","award":["Open Access Funding Programme"],"award-info":[{"award-number":["Open Access Funding Programme"]}],"id":[{"id":"https:\/\/ror.org\/04d836q62","id-type":"ROR","asserted-by":"crossref"}]},{"name":"COMET Centre CHASE"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,10,6]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Optical photothermal infrared (O-PTIR) spectroscopy is an indirect mid-infrared spectral imaging technique that enables label-free chemical analysis with submicrometer resolution. The technique is often used for analyzing cells and tissues and is discussed as capable of measuring in aqueous media, yet a quantitative understanding of its signal formation in liquids remains incomplete. Here, we present a systematic experimental study of transmission-mode O-PTIR supported by detailed simulations on the underlying signal generating process, focusing on O-PTIR applied to a water filled cuvette comprising two CaF2 windows with a path length of 600 \u03bcm, by finite element analysis. We investigate the influence of moving the focal spot of the excitation mid-IR beam from the window-liquid interface into the liquid and link excitation parameters to thermal dynamics and observed readout by the probe beam. We show that the signal amplitude is governed by the pulse duration, which controls the deposited thermal energy, while the modulation frequency determines the thermal diffusion length and thus the spatial extent of the response. Depth-resolved and probe-position-dependent measurements reveal a nonlocal photothermal response dominated by refractive index gradients associated with the photothermal lens effect involving both the liquid and the windows. Time-resolved analysis further separates the temperature field into a large steady-state (DC) component and a smaller oscillatory (AC) contribution, with the latter increasing at lower modulation frequencies and both decreasing with shorter pulse durations. These results establish a unified physical picture of O-PTIR signal generation and provide a basis for practical guidelines for optimizing sensitivity, spatial resolution, and quantitative performance in liquid-phase O-PTIR measurements.<\/jats:p>","DOI":"10.1021\/acsomega.6c10332","type":"journal-article","created":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T12:02:18Z","timestamp":1790337738000},"page":"60485-60493","source":"Crossref","is-referenced-by-count":0,"title":["Demystifying Experimental Parameters in Optical Photothermal\nImaging in Aqueous Media"],"prefix":"10.1021","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-9282-4474","authenticated-orcid":true,"given":"Nikolaus","family":"Hondl","sequence":"first","affiliation":[{"name":"TU Wien , , ,","place":["Vienna, Austria, 1060"]},{"name":"TU Wien , , ,","place":["Wien, Austria, 1060"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nelson G. C.","family":"Astrath","sequence":"additional","affiliation":[{"name":"TU Wien , , ,","place":["Vienna, Austria, 1060"]},{"name":"Universidade Estadual de Maringa\u0301 , , , ,","place":["Maringa\u0301, Parana\u0301, Brazil, 87020-900"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-0703-9524","authenticated-orcid":true,"given":"Elisabeth","family":"Holub","sequence":"additional","affiliation":[{"name":"TU Wien , , ,","place":["Vienna, Austria, 1060"]},{"name":"TU Wien , , ,","place":["Wien, Austria, 1060"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3838-5842","authenticated-orcid":true,"given":"Bernhard","family":"Lendl","sequence":"additional","affiliation":[{"name":"TU Wien , , ,","place":["Vienna, Austria, 1060"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8307-5435","authenticated-orcid":true,"given":"Georg","family":"Ramer","sequence":"additional","affiliation":[{"name":"TU Wien , , ,","place":["Vienna, Austria, 1060"]},{"name":"TU Wien , , ,","place":["Wien, Austria, 1060"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,9,25]]},"reference":[{"issue":"2","key":"2026100610484443200_cit1","doi-asserted-by":"publisher","first-page":"1378","DOI":"10.1364\/OE.19.001378","article-title":"High Resolution\nCellular Imaging with Nonlinear Optical\nInfrared Microscopy","volume":"19","author":"Lee","year":"2011","journal-title":"Opt. Express"},{"issue":"9","key":"2026100610484443200_cit2","doi-asserted-by":"publisher","first-page":"4863","DOI":"10.1021\/acs.analchem.6b04638","article-title":"Mid-Infrared Photothermal\nImaging of Active Pharmaceutical Ingredients at Submicrometer Spatial\nResolution","volume":"89","author":"Li","year":"2017","journal-title":"Anal. Chem."},{"issue":"3","key":"2026100610484443200_cit3","doi-asserted-by":"publisher","first-page":"26","DOI":"10.1017\/S1551929520000917","article-title":"Optical Photothermal\nInfrared Microspectroscopy with Simultaneous Raman \u2013 A New\nNon-Contact Failure Analysis Technique for Identification of &lt;\n10 \u039cm Organic Contamination in the Hard Drive and Other Electronics\nIndustries","volume":"28","author":"Kansiz","year":"2020","journal-title":"Microsc. Today"},{"issue":"43","key":"2026100610484443200_cit4","doi-asserted-by":"publisher","first-page":"8597","DOI":"10.1021\/acs.jpcb.2c05827","article-title":"Mid-Infrared Photothermal Microscopy:\nPrinciple, Instrumentation, and Applications","volume":"126","author":"Xia","year":"2022","journal-title":"J. Phys. Chem. B"},{"issue":"9","key":"2026100610484443200_cit5","doi-asserted-by":"publisher","DOI":"10.1063\/5.0219983","article-title":"A Tutorial\non Optical Photothermal\nInfrared (O-PTIR) Microscopy","volume":"9","author":"Prater","year":"2024","journal-title":"APL Photonics"},{"key":"2026100610484443200_cit6","unstructured":"Furstenberg, R.; Kendziora, C. A.; Papantonakis, M. R.; Nguyen, V.; McGill, R. A. In  Chemical\nImaging Using Infrared Photothermal Microspectroscopy, SPIE\nProceedings; Druy, M. A.; Crocombe, R. A., Eds.; SPIE: Baltimore,\nMaryland, USA, 201283741110.1117\/12.919574."},{"key":"2026100610484443200_cit7","doi-asserted-by":"publisher","DOI":"10.1364\/CLEO_AT.2014.AF1B.4","volume-title":"Label Free Mid-IR\nPhotothermal Imaging of Bird Brain With Quantum Cascade Laser","author":"Me\u0308rtiri","year":"2014"},{"issue":"14","key":"2026100610484443200_cit8","doi-asserted-by":"publisher","first-page":"9932","DOI":"10.1021\/acs.analchem.0c01495","article-title":"Simultaneous Optical\nPhotothermal Infrared (O-PTIR) and Raman Spectroscopy of Submicrometer\nAtmospheric Particles","volume":"92","author":"Olson","year":"2020","journal-title":"Anal. Chem."},{"key":"2026100610484443200_cit9","doi-asserted-by":"publisher","first-page":"1189","DOI":"10.1063\/1.2926816","volume-title":"Comparison Between\nMode-Matched and Mode-Mismatched Thermal Lens Methods for Absorption\nMeasurements in Liquids","author":"Marcano","year":"2008"},{"issue":"8","key":"2026100610484443200_cit10","doi-asserted-by":"publisher","first-page":"3732","DOI":"10.1063\/1.356045","article-title":"Mode-Mismatched\nThermal Lens Determination\nof Temperature Coefficient of Optical Path Length in Soda Lime Glass\nat Different Wavelengths","volume":"75","author":"Baesso","year":"1994","journal-title":"J. Appl. Phys."},{"issue":"1","key":"2026100610484443200_cit11","doi-asserted-by":"publisher","first-page":"877","DOI":"10.1063\/1.1524039","article-title":"Thermal\nLens Determination of the Temperature Coefficient of Optical Path\nLength in Optical Materials","volume":"74","author":"Andrade","year":"2003","journal-title":"Rev. Sci. Instrum."},{"issue":"1","key":"2026100610484443200_cit12","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-022-23318-2","article-title":"Optical Photothermal Infrared Spectroscopy\nwith Simultaneously Acquired Raman Spectroscopy for Two-Dimensional\nMicroplastic Identification","volume":"12","author":"Bo\u0308ke","year":"2022","journal-title":"Sci. Rep."},{"issue":"1","key":"2026100610484443200_cit13","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-025-26751-1","article-title":"Method for Label-Free & Non-Destructive\nDetection of Microplastics in Human Formalin-Fixed Paraffin-Embedded\nTissue Sections","volume":"15","author":"Gruber","year":"2025","journal-title":"Sci. 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Adv."},{"issue":"1","key":"2026100610484443200_cit20","doi-asserted-by":"publisher","DOI":"10.1038\/s41467-023-44675-0","article-title":"Single-Cell\nMapping of Lipid Metabolites\nUsing an Infrared Probe in Human-Derived Model Systems","volume":"15","author":"Bai","year":"2024","journal-title":"Nat. Commun."},{"key":"2026100610484443200_cit21","doi-asserted-by":"crossref","unstructured":"Shuster, S. O.; Curtis, A. E.; Davis, C. M.\n          Optical Photothermal\nInfrared Imaging Using Metabolic Probes in Biological Systems\n          Biophysics\n          2024; Vol. 9710.1101\/2024.09.19.613881.","DOI":"10.1101\/2024.09.19.613881"},{"issue":"8","key":"2026100610484443200_cit22","doi-asserted-by":"publisher","first-page":"3938","DOI":"10.1021\/acs.analchem.0c04846","article-title":"Analysis of\nFixed and Live Single Cells Using Optical Photothermal Infrared with\nConcomitant Raman Spectroscopy","volume":"93","author":"Spadea","year":"2021","journal-title":"Anal. Chem."},{"issue":"39","key":"2026100610484443200_cit23","doi-asserted-by":"publisher","first-page":"21418","DOI":"10.1021\/acs.analchem.5c03194","article-title":"Not Just Better\nResolution: A Detailed Study of the Signal Distribution in Mid-Infrared\nOptical Photothermal Imaging","volume":"97","author":"Holub","year":"2025","journal-title":"Anal. Chem."},{"issue":"1","key":"2026100610484443200_cit24","doi-asserted-by":"publisher","first-page":"96","DOI":"10.1021\/acsmeasuresciau.5c00132","article-title":"Investigating Spectral\nBiomarker Candidates for Migratory Potential in Cancer Cells Using\nMicro-FTIR and O-PTIR Spectroscopy","volume":"6","author":"Holub","year":"2026","journal-title":"ACS Meas.\nSci. 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Bioanal.\nChem."},{"issue":"10","key":"2026100610484443200_cit27","doi-asserted-by":"publisher","first-page":"1274","DOI":"10.1177\/0003702820937364","article-title":"An Experimental\nInvestigation of Sample\u2013Fluid Heat Coupling Effect in Thermal\nLens Technique","volume":"74","author":"Lukasievicz","year":"2020","journal-title":"Appl. Spectrosc."},{"issue":"4","key":"2026100610484443200_cit28","doi-asserted-by":"publisher","DOI":"10.1063\/5.0015996","article-title":"Influence of\nEdge Effects on Laser-Induced Surface Displacement of Opaque Materials\nby Photothermal Interferometry","volume":"128","author":"Flizikowski","year":"2020","journal-title":"J. Appl. Phys."},{"key":"2026100610484443200_cit29","unstructured":"Byrnes, S. J.\n          \n          Multilayer\nOptical Calculations. 2020, arXiv:1603.02720.\narXiv.org e-Print archive. https:\/\/arxiv.org\/abs\/1603.0272010.48550\/arXiv.1603.02720."},{"key":"2026100610484443200_cit30","unstructured":"Byrnes, S. J.\n          \n          Tmm\n          2024, https:\/\/pypi.org\/project\/tmm\/. (accessed 2026\u201304\u201305)."},{"issue":"3","key":"2026100610484443200_cit31","doi-asserted-by":"publisher","DOI":"10.1364\/AO.12.000555","article-title":"Optical Constants of Water in the 200-Nm to 200-\u039cm\nWavelength Region","volume":"12","author":"Hale","year":"1973","journal-title":"Appl. Opt."},{"issue":"11","key":"2026100610484443200_cit32","doi-asserted-by":"publisher","DOI":"10.1364\/AO.2.001103","article-title":"A Redetermination\nof Some Optical Properties of Calcium Fluoride","volume":"2","author":"Malitson","year":"1963","journal-title":"Appl. Opt."},{"issue":"1","key":"2026100610484443200_cit33","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-024-66977-z","article-title":"An Optical\nPhotothermal Infrared Investigation of Lymph Nodal Metastases of Oral\nSquamous Cell Carcinoma","volume":"14","author":"Al Jedani","year":"2024","journal-title":"Sci. Rep."}],"container-title":["ACS Omega"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acsomega.6c10332","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/acsodf\/article-pdf\/11\/39\/60485\/68649860\/acsomega.6c10332.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/acsodf\/article-pdf\/11\/39\/60485\/68649860\/acsomega.6c10332.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T15:19:42Z","timestamp":1791299982000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/acsodf\/article\/11\/39\/60485\/5438334\/Demystifying-Experimental-Parameters-in-Optical"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,25]]},"references-count":33,"journal-issue":{"issue":"39","published-online":{"date-parts":[[2026,9,25]]},"published-print":{"date-parts":[[2026,10,6]]}},"URL":"https:\/\/doi.org\/10.1021\/acsomega.6c10332","relation":{},"ISSN":["2470-1343"],"issn-type":[{"value":"2470-1343","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,25]]}}}