{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T01:38:14Z","timestamp":1787794694593,"version":"build-2784847793"},"reference-count":20,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2023,10,7]],"date-time":"2023-10-07T00:00:00Z","timestamp":1696636800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"A*STAR, SERC Thermoelectric Materials Program","award":["1527200019"],"award-info":[{"award-number":["1527200019"]}]},{"name":"A*STAR, SERC Thermoelectric Materials Program","award":["1527200024"],"award-info":[{"award-number":["1527200024"]}]},{"name":"A*STAR, SERC Thermoelectric Materials Program","award":["1527200021"],"award-info":[{"award-number":["1527200021"]}]},{"name":"A*STAR, SERC Thermoelectric Materials Program","award":["A19D9a0096"],"award-info":[{"award-number":["A19D9a0096"]}]},{"DOI":"10.13039\/501100001348","name":"Sustainable Hybrid Lighting System for Controlled Environment Agriculture Program","doi-asserted-by":"publisher","award":["1527200019"],"award-info":[{"award-number":["1527200019"]}],"id":[{"id":"10.13039\/501100001348","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001348","name":"Sustainable Hybrid Lighting System for Controlled Environment Agriculture Program","doi-asserted-by":"publisher","award":["1527200024"],"award-info":[{"award-number":["1527200024"]}],"id":[{"id":"10.13039\/501100001348","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001348","name":"Sustainable Hybrid Lighting System for Controlled Environment Agriculture Program","doi-asserted-by":"publisher","award":["1527200021"],"award-info":[{"award-number":["1527200021"]}],"id":[{"id":"10.13039\/501100001348","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001348","name":"Sustainable Hybrid Lighting System for Controlled Environment Agriculture Program","doi-asserted-by":"publisher","award":["A19D9a0096"],"award-info":[{"award-number":["A19D9a0096"]}],"id":[{"id":"10.13039\/501100001348","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>With chronic ocular diseases such as glaucoma and dry eye syndrome, patients have to apply eye drops over the long term. The therapeutic effects of eye drops depend on the amount of drug contained and the stability of the solution. In addition, contamination during usage and transport can also negatively affect the quality and efficacy of eye drops. The current techniques for the characterization of eye drops are often complicated and time-consuming. Developing a fast and non-invasive way of accurately measuring eye drop quality remains an ongoing challenge. The biggest challenge and primary prerequisite for the application of this new detection technique for eye drops is the obtention of a sufficient spectral response and resolvable signal, considering the large background signal contributed by water. In this work, we use terahertz (THz) attenuated total reflection (ATR) spectroscopy combined with a sensitive hybrid graphene oxide (GO) and carbon nanotube (CNT) thin-film sensors to obtain distinct THz spectral signals in commercial eye drops. Various commercial eye drop products have been tested, and we show that they can be differentiated via their spectral signals. Our results provide a solid foundation for the future fine analysis of eye drops and the detection of their quality. Furthermore, THz spectroscopy combined with GO\/CNT films has significant potential and advantages for the non-destructive characterization of aqueous pharmaceutical products.<\/jats:p>","DOI":"10.3390\/s23198290","type":"journal-article","created":{"date-parts":[[2023,10,9]],"date-time":"2023-10-09T06:16:48Z","timestamp":1696832208000},"page":"8290","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Terahertz Attenuated Total Reflection Spectral Response and Signal Enhancement via Plasmonic Enhanced Sensor for Eye Drop Detection"],"prefix":"10.3390","volume":"23","author":[{"given":"Eugene Soh Jia","family":"Hao","sequence":"first","affiliation":[{"name":"Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qiang","family":"Zhu","sequence":"additional","affiliation":[{"name":"Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634, Singapore"},{"name":"Institution of Sustainability for Chemical, Energy and Environment (ISCE2), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore"},{"name":"School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5831-0699","authenticated-orcid":false,"given":"Xizu","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karen Ke","family":"Lin","sequence":"additional","affiliation":[{"name":"Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore 138634, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,10,7]]},"reference":[{"key":"ref_1","unstructured":"Florence, A., and Attwood, D. 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