{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T17:09:20Z","timestamp":1785431360141,"version":"3.56.0"},"reference-count":51,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T00:00:00Z","timestamp":1779148800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002641","name":"Konkuk University","doi-asserted-by":"publisher","award":["2024"],"award-info":[{"award-number":["2024"]}],"id":[{"id":"10.13039\/501100002641","id-type":"DOI","asserted-by":"publisher"}]},{"award":["2024"],"award-info":[{"award-number":["2024"]}],"id":[{"id":"https:\/\/ror.org\/025h1m602","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["20026593 and 00418987"],"award-info":[{"award-number":["20026593 and 00418987"]}],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]},{"award":["20026593 and 00418987"],"award-info":[{"award-number":["20026593 and 00418987"]}],"id":[{"id":"https:\/\/ror.org\/008nkqk13","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Copper is an indispensable trace element for maintaining metabolic homeostasis; however, the dysregulation and subsequent accumulation of Cu2+ are critically linked to neurodegenerative pathologies, including Alzheimer\u2019s disease in humans. Consequently, the development of robust analytical tools for Cu2+ monitoring is of paramount importance. Here, we report a 2,2\u2032-dipicolylamine porphyrin (DPAP)-based fluorescent sensor designed for the precise detection of metal cations. Photophysical investigations reveal that DPAP operates via a rapid turn-off fluorescence mechanism, achieving high-performance sensing in the parts-per-million range. Notably, the probe demonstrates exceptional sensitivity with detection limits of 26.3 nM for Cu2+ and 34.8 nM for Ni2+. Interference studies demonstrated the selectivity of DPAP for Cu2+ over a diverse range of competing metal ions such as Na+, Ag+, Ni2+, Cr3+, Pb2+, Al3+, Fe2+, Cd2+, and Zn2+. These results indicate that DPAP is a sensitive and selective probe suitable for copper ion detection.<\/jats:p>","DOI":"10.3390\/molecules31101739","type":"journal-article","created":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T16:07:26Z","timestamp":1779206846000},"page":"1739","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Porphyrin-Based Fluorescent Probe for Nanomolar Detection of Cu2+ and Ni2+ Ions"],"prefix":"10.3390","volume":"31","author":[{"given":"So-Hyun","family":"Shin","sequence":"first","affiliation":[{"name":"Department of Materials Science and Engineering, Konkuk University, 120 Neungdong\u2013ro, Gwangjin\u2013gu, Seoul 05029, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jihyun","family":"Kim","sequence":"additional","affiliation":[{"name":"Advanced Materials Program, Department of Materials Science and Engineering, Konkuk University, 120 Neungdong\u2013ro, Gwangjin\u2013gu, Seoul 05209, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hyungkyu","family":"Moon","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Konkuk University, 120 Neungdong\u2013ro, Gwangjin\u2013gu, Seoul 05029, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T.","family":"Sheshashena Reddy","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Konkuk University, 120 Neungdong\u2013ro, Gwangjin\u2013gu, Seoul 05029, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Myung-Seok","family":"Choi","sequence":"additional","affiliation":[{"name":"Advanced Materials Program, Department of Materials Science and Engineering, Konkuk University, 120 Neungdong\u2013ro, Gwangjin\u2013gu, Seoul 05209, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.jphotochem.2017.11.003","article-title":"A Novel Fluorescence Sensor for Dual Sensing of Hg2+ and Cu2+ Ions","volume":"353","author":"Sie","year":"2018","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2203","DOI":"10.1021\/acs.chemrev.6b00021","article-title":"Development of Ion Chemosensors Based on Porphyrin Analogues","volume":"117","author":"Ding","year":"2017","journal-title":"Chem. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3333","DOI":"10.1021\/acs.analchem.5b04892","article-title":"Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission","volume":"88","author":"Neupane","year":"2016","journal-title":"Anal. Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/j.saa.2017.03.010","article-title":"Multi-Signaling Thiocarbohydrazide Based Colorimetric Sensors for the Selective Recognition of Heavy Metal Ions in an Aqueous Medium","volume":"180","author":"Momidi","year":"2017","journal-title":"Spectrochim. Acta A Mol. Biomol. Spectrosc."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"9226","DOI":"10.1021\/ic300661c","article-title":"A Highly Selective Fluorescent Sensor for Distinguishing Cadmium from Zinc Ions Based on a Quinoline Platform","volume":"51","author":"Zhou","year":"2012","journal-title":"Inorg. Chem."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1016\/j.dyepig.2016.12.023","article-title":"A Highly Selective Fluorescent Sensor for Cd2+ Based on a New Diarylethene with a 1,8-Naphthyridine Unit","volume":"139","author":"Zhang","year":"2017","journal-title":"Dye. Pigment."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"3656","DOI":"10.1021\/ol201305d","article-title":"Red-Emission Fluorescent Probe Sensing Cadmium and Pyrophosphate Selectively in Aqueous Solution","volume":"13","author":"Cheng","year":"2011","journal-title":"Org. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1091","DOI":"10.1039\/c8pp00137e","article-title":"A Naked-Eye Fluorescent Sensor for Copper(Ii) Ions Based on a Naphthalene Conjugate Bodipy Dye","volume":"17","author":"Baslak","year":"2018","journal-title":"Photochem. Photobiol. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"12537","DOI":"10.1021\/acsomega.9b00970","article-title":"Highly Sensitive Dansyl-Based Chemosensor for Detection of Cu2+ in Aqueous Solution and Zebrafish","volume":"4","author":"Chae","year":"2019","journal-title":"ACS Omega"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2703","DOI":"10.1016\/j.tetlet.2016.04.090","article-title":"A Highly Selective Fluorescent Sensor for Dual Detection of Zn2+ and F\u2212 Based on a New Diarylethene","volume":"57","author":"Tian","year":"2016","journal-title":"Tetrahedron Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1016\/j.jlumin.2017.02.019","article-title":"An Aggregation Induced Emission Enhancement-Based Ratiometric Fluorescent Sensor for Detecting Trace Uranyl Ion (UO22+) and the Application in Living Cells Imaging","volume":"186","author":"Chen","year":"2017","journal-title":"J. Lumin."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"427","DOI":"10.1016\/j.dyepig.2017.05.001","article-title":"A Porphyrin-Based Fluorescent Probe for Optical Detection of Toxic Cd2+ Ion in Aqueous Solution and Living Cells","volume":"143","author":"Huang","year":"2017","journal-title":"Dye. Pigment."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2119","DOI":"10.1016\/j.dib.2018.06.096","article-title":"Data on a Real-Time Tripodal Colorimetric\/Fluorescence Sensor for Multiple Target Metal Ions","volume":"19","author":"Diana","year":"2018","journal-title":"Data Brief"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"10041","DOI":"10.1021\/ic2008182","article-title":"A Highly Selective On\/Off Fluorescence Sensor for Cadmium(II)","volume":"50","author":"Zhao","year":"2011","journal-title":"Inorg. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2576","DOI":"10.1002\/slct.201600504","article-title":"2-(2,2-Bis-Benzylamino-1-Cyano-Vinyl)-Benzonitrile: A Selective Turn-off Fluorescent Cu2+ Sensor","volume":"1","author":"Singh","year":"2016","journal-title":"ChemistrySelect"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1656","DOI":"10.1016\/j.inoche.2011.06.032","article-title":"Fluoranthene-Based Pyridine as Fluorescent Chemosensor for Fe3+","volume":"14","author":"Li","year":"2011","journal-title":"Inorg. Chem. Commun."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"274","DOI":"10.1016\/j.snb.2014.03.033","article-title":"Fluorescent Sensor for Hg2+ Detection in Aqueous Solution","volume":"198","author":"Han","year":"2014","journal-title":"Sens. Actuators B Chem."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"115580","DOI":"10.1016\/j.optmat.2024.115580","article-title":"A Fluorescein Conjugate as Colorimetric and Red-Emissive Fluorescence Chemosensor for Selective Recognition Cu2+ Ions","volume":"153","author":"Zavalishin","year":"2024","journal-title":"Opt. Mater."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"109464","DOI":"10.1016\/j.bioorg.2025.109464","article-title":"A Novel Fluorescent Probe for Sensitive Detection Copper in Food Samples and in Vivo","volume":"170","author":"Ye","year":"2026","journal-title":"Bioorg. Chem."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1016\/j.snb.2011.10.036","article-title":"Aldazine-Based Colorimetric Sensors for Cu2+ and Fe3+","volume":"161","author":"Narayanaswamy","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Bagheri, S., Squitti, R., Haertl\u00e9, T., Siotto, M., and Saboury, A.A. (2018). Role of Copper in the Onset of Alzheimer\u2019s Disease Compared to Other Metals. Front. Aging Neurosci., 9.","DOI":"10.3389\/fnagi.2017.00446"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.snb.2013.10.093","article-title":"A Novel BODIPY-Based Colorimetric and Fluorometric Dual-Mode Chemosensor for Hg2+ and Cu2+","volume":"192","author":"He","year":"2014","journal-title":"Sens. Actuators B Chem."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"4390","DOI":"10.1016\/j.tet.2018.07.002","article-title":"A Highly Selective Fluorescence Switch for Cu2+ and Fe3+ Based on a New Diarylethene with a Triazole-Linked Rhodamine 6G Unit","volume":"74","author":"Kang","year":"2018","journal-title":"Tetrahedron"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"657","DOI":"10.1016\/j.saa.2018.06.094","article-title":"Dual-Functional Probe Based on Rhodamine for Sequential Cu2+ and ATP Detection in Vivo","volume":"204","author":"Jin","year":"2018","journal-title":"Spectrochim. Acta A Mol. Biomol. Spectrosc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1197","DOI":"10.1039\/c8pp00157j","article-title":"Fluorescence \u201coff\u201d and \u201con\u201d Signalling of Esculetin in the Presence of Copper and Thiol: A Possible Implication in Cellular Thiol Sensing","volume":"17","author":"Shinde","year":"2018","journal-title":"Photochem. Photobiol. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1016\/j.snb.2013.04.109","article-title":"Rapid and Highly Selective Relay Recognition of Cu(II) and Sulfide Ions by a Simple Benzimidazole-Based Fluorescent Sensor in Water","volume":"185","author":"Tang","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1016\/j.dyepig.2012.09.019","article-title":"A New Selective Pyrazoline-Based Fluorescent Chemosensor for Cu2+ in Aqueous Solution","volume":"96","author":"Hu","year":"2013","journal-title":"Dye. Pigment."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1016\/j.saa.2013.11.091","article-title":"Relay Recognition of Cu2+ and S2\u2212 in Water by a Simple 2-(2\u2032-Aminophenyl)Benzimidazole Derivatized Fluorescent Sensor through Modulating ESIPT","volume":"122","author":"Tang","year":"2014","journal-title":"Spectrochim. Acta A Mol. Biomol. Spectrosc."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"492","DOI":"10.1021\/ol3032889","article-title":"A Fluorescent Ratiometric Chemodosimeter for Cu2+ Based on TBET and Its Application in Living Cells","volume":"15","author":"Fan","year":"2013","journal-title":"Org. Lett."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1016\/j.snb.2016.08.020","article-title":"A Colorimetric and Fluorescent Sensor for Cu2+ and F\u2212 Based on a Diarylethene with a 1,8-Naphthalimide Schiff Base Unit","volume":"239","author":"Fu","year":"2017","journal-title":"Sens. Actuators B Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"697528","DOI":"10.1155\/2010\/697528","article-title":"Use of Tetra-Ammonium Tetrakis(4-Sulphonato)Phenyl Porphyrin for Pseudomonas and Bacillus Cell Imaging","volume":"2010","author":"Sujatha","year":"2010","journal-title":"Int. J. Anal. Chem."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4690","DOI":"10.1039\/C6TB01159D","article-title":"Decoration of Porphyrin with Tetraphenylethene: Converting a Fluorophore with Aggregation-Caused Quenching to Aggregation-Induced Emission Enhancement","volume":"4","author":"Guo","year":"2016","journal-title":"J. Mater. Chem. B"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"4351","DOI":"10.1039\/D5AY00524H","article-title":"A Water-Soluble Fluorescent Probe Based on Porphyrin Derivatives for Cu2+ Detection in Aqueous Solution and Living Cells","volume":"17","author":"Chen","year":"2025","journal-title":"Anal. Methods"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"894","DOI":"10.1002\/slct.201702382","article-title":"Fabrication of a Paper-Based Turn-Off Fluorescence Sensor for Cu2+ Ion from a Pyridinium Porphyrin","volume":"3","author":"Prabphal","year":"2018","journal-title":"ChemistrySelect"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"7749","DOI":"10.1021\/ic061709v","article-title":"A Copper(II) Ion-Selective on-off-Type Fluoroionophore Based on Zinc Porphyrin-Dipyridylamino","volume":"46","author":"Weng","year":"2007","journal-title":"Inorg. Chem."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"100058","DOI":"10.1016\/j.rechem.2020.100058","article-title":"Colorimetric and Fluorescent On-off Detection of Cu2+, Sn2+ and Zn2+ by a Water-Soluble Porphyrin: Electronic Absorption and Emission Study","volume":"2","author":"Beyene","year":"2020","journal-title":"Results Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.snb.2017.03.016","article-title":"A Water-Soluble, Cationic Bis-Porphyrin Exhibiting a More Sensitive Fluorescent Response to Cu2+ Relative to Its Monomeric Counterpart","volume":"247","author":"Liu","year":"2017","journal-title":"Sens. Actuators B Chem."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"5485","DOI":"10.1039\/c2cc30258f","article-title":"Selective Colorimetric Sensing of Co(Ii) in Aqueous Media with a Spiropyran-Amide-Dipicolylamine Linkage under UV Irradiation","volume":"48","author":"Shiraishi","year":"2012","journal-title":"Chem. Commun."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.molstruc.2016.02.022","article-title":"Novel Cobalt(II) Complexes Containing N,N-Di(2-Picolyl)Amine Based Ligands; Synthesis, Characterization and Application towards Methyl Methacrylate Polymerisation","volume":"1113","author":"Ahn","year":"2016","journal-title":"J. Mol. Struct."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.jorganchem.2015.02.011","article-title":"Cadmium(II) Complexes Containing N\u2032-Substituted N,N-Di(2-Picolyl)Amine: The Formation of Monomeric versus Dimeric Complexes is Affected by the N\u2032-Substitution Group on the Amine Moiety","volume":"783","author":"Song","year":"2015","journal-title":"J. Organomet. Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"e4383","DOI":"10.1002\/aoc.4383","article-title":"Diisopropyl Fluorophosphate (DFP) Degradation Activity Using Transition Metal\u2013Dipicolylamine Complexes","volume":"32","author":"Jeong","year":"2018","journal-title":"Appl. Organomet. Chem."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1016\/j.poly.2015.12.043","article-title":"Synthesis, Characterization, X-Ray Crystallography Analysis, and Catalytic Activity of Bis(2-Pyridylmethyl)Amine Copper Complexes Containing Coupled Pendent Olefinic Arms in Atom Transfer Radical Addition (ATRA) Reactions","volume":"114","author":"Bussey","year":"2016","journal-title":"Polyhedron"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1016\/j.poly.2010.12.005","article-title":"Nickel(II) and Zinc(II) Complexes of N-Substituted Di(2-Picolyl)Amine Derivatives: Synthetic and Structural Studies","volume":"30","author":"Gloe","year":"2011","journal-title":"Polyhedron"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1016\/j.jorganchem.2017.03.036","article-title":"Redox-Active Metal Complexes with 2,2\u2032-Dipicolylamine Containing Ferrocenyl Moiety: Synthesis, Electrochemical Behavior and Biological Activity","volume":"839","author":"Milaeva","year":"2017","journal-title":"J. Organomet. Chem."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"6062","DOI":"10.1039\/c2ob07118e","article-title":"Dipicolylamine as a Unique Structural Switching Element for Helical Peptides","volume":"10","author":"Azuma","year":"2012","journal-title":"Org. Biomol. Chem."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"107721","DOI":"10.1016\/j.dyepig.2019.107721","article-title":"A Selective Triarylmethine-Based Spectroscopic Probe for Zn2+ Ion Monitoring","volume":"171","author":"Lee","year":"2019","journal-title":"Dye. Pigment."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"2864","DOI":"10.1021\/jo982452o","article-title":"Investigation of Conditions Giving Minimal Scrambling in the Synthesis of Trans-Porphyrins from Dipyrromethanes and Aldehydes","volume":"64","author":"Littler","year":"1999","journal-title":"J. Org. Chem."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.jphotochemrev.2017.06.002","article-title":"Fluorescent Chemosensors for Copper(II) Ion: Structure, Mechanism and Application","volume":"32","author":"Liu","year":"2017","journal-title":"J. Photochem. Photobiol. C Photochem. Rev."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1002\/bio.1205","article-title":"Fluorescence Quenching Studies of Nitrated Polycyclic Aromatic Hydrocarbons","volume":"26","author":"Miller","year":"2011","journal-title":"Luminescence"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"175","DOI":"10.4314\/wsa.v40i1.21","article-title":"Fluorescent Sensing and Determination of Mercury (II) Ions in Water","volume":"40","author":"Ncube","year":"2014","journal-title":"Water SA"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1059","DOI":"10.1002\/cplu.201402016","article-title":"A Probe for the Selective and Parts-per-Billion-Level Detection of Copper(II) and Mercury(II) Using a Micellar Medium and Its Utility in Cell Imaging","volume":"79","author":"Kumari","year":"2014","journal-title":"Chempluschem"}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/10\/1739\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,23]],"date-time":"2026-05-23T04:18:54Z","timestamp":1779509934000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/10\/1739"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,19]]},"references-count":51,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["molecules31101739"],"URL":"https:\/\/doi.org\/10.3390\/molecules31101739","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,19]]}}}