{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T08:39:42Z","timestamp":1786523982828,"version":"build-2736575974"},"reference-count":63,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T00:00:00Z","timestamp":1786492800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007414","name":"Qassim University","doi-asserted-by":"publisher","award":["QU-APC-2026"],"award-info":[{"award-number":["QU-APC-2026"]}],"id":[{"id":"10.13039\/501100007414","id-type":"DOI","asserted-by":"publisher"}]},{"award":["QU-APC-2026"],"award-info":[{"award-number":["QU-APC-2026"]}],"id":[{"id":"https:\/\/ror.org\/01wsfe280","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biosensors"],"abstract":"<jats:p>During this research, a distinctive optical sensor film was devised and designed to detect Cu(II). The 3-acetyl-4-hydroxyquinolin-2(1H)-one (AHQ) sensor probe is effectively synthesized. This organic probe of the sensor film exhibits exceptional sensitivity to Cu(II) ions and a \u201cturn-off\u201d state. This innovative fluorescent chemosensor is distinguished by its unique optical characteristics, which include a significant Stokes shift of approximately 91 nm. The binding of Cu(II) with AHQ organic probe introduces a 1:2 (metal:ligand) complex, accompanied by the quenching of the maximum emission peak at 455. Furthermore, AHQ exhibits exceptional selectivity for Cu(II). The quenching of the complex fluorescence is attributed to internal charge transfer (ICT), as indicated by the mechanism. The AHQ sensing molecule for Cu(II) ions is attributed to chelation-quenched fluorescence. Density functional theory (DFT) and time-dependent DFT (TDDFT) were employed to study the binding of Cu(II)\u2013AHQ structures and related electronic characteristics in solutions. The results reveal that the luminescence quenching of this complex is caused by ICT. The influences of the interference ions were investigated using a solution that contained multiple metal ions. This AHQ molecule exhibits exceptional selectivity and sensitivity and a low LOD of 10.8 nM, and is administered in a physiological pH medium (pH = 7.4) with a relative standard deviation (RSDr) (1%, n = 3). Also, the AHQ shows good binding behaviour towards Cu(II), and the binding constant was determined to be 3.8 \u00d7 106 M\u22121. As a result, these unique characteristics allow it to identify Cu(II) within a controlled dynamic range of 0.019\u20132.4 \u03bcM Cu(II). The reversibility of the chemosensor was established by using EDTA as a strong chelating agent. As a highlight, we present an important optical chemosensor dependent on the AHQ molecule.<\/jats:p>","DOI":"10.3390\/bios16080436","type":"journal-article","created":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T07:57:26Z","timestamp":1786521446000},"page":"436","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Novel Optical Sensor-Based Organic Chromophore for the Detection of Copper Ions"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3104-7613","authenticated-orcid":false,"given":"Reham","family":"Ali","sequence":"first","affiliation":[{"name":"Department of Chemistry, College of Science, Qassim University, Buraidah 51452, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Majd K.","family":"Almotiri","sequence":"additional","affiliation":[{"name":"Department of Chemistry, College of Science, Qassim University, Buraidah 51452, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0485-4997","authenticated-orcid":false,"given":"Sabri","family":"Messaoudi","sequence":"additional","affiliation":[{"name":"Department of Chemistry, College of Science, Qassim University, Buraidah 51452, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ibrahim A. I.","family":"Ali","sequence":"additional","affiliation":[{"name":"Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 8366004, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3866-2304","authenticated-orcid":false,"given":"Azizah","family":"Algreiby","sequence":"additional","affiliation":[{"name":"Department of Chemistry, College of Science, Qassim University, Buraidah 51452, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2677-0439","authenticated-orcid":false,"given":"Sayed M.","family":"Saleh","sequence":"additional","affiliation":[{"name":"Department of Chemistry, College of Science, Qassim University, Buraidah 51452, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"8441","DOI":"10.3390\/cimb46080498","article-title":"Is Copper Still Safe for Us? 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