{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:28:02Z","timestamp":1772252882346,"version":"3.50.1"},"reference-count":73,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2017,10,6]],"date-time":"2017-10-06T00:00:00Z","timestamp":1507248000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Malaysian Ministry of Higher Education (MOHE)","award":["FRGS\/1\/2015\/TK04\/UKM\/02\/3"],"award-info":[{"award-number":["FRGS\/1\/2015\/TK04\/UKM\/02\/3"]}]},{"name":"Malaysian Ministry of Higher Education (MOHE)","award":["FRGS\/1\/2016\/TK04\/UKM\/02\/7"],"award-info":[{"award-number":["FRGS\/1\/2016\/TK04\/UKM\/02\/7"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The study of binding affinity is essential in surface plasmon resonance (SPR) sensing because it allows researchers to quantify the affinity between the analyte and immobilised ligands of an SPR sensor. In this study, we demonstrate the derivation of the binding affinity constant, K, for Pb2+ and Hg2+ ions according to their SPR response using a gold\/silver\/gold\/chitosan\u2013graphene oxide (Au\/Ag\/Au\/CS\u2013GO) sensor for the concentration range of 0.1\u20135 ppm. The higher affinity of Pb2+ to binding with the CS\u2013GO sensor explains the outstanding sensitivity of 2.05 \u00b0ppm\u22121 against 1.66 \u00b0ppm\u22121 of Hg2+. The maximum signal-to-noise ratio (SNR) upon detection of Pb2+ is 1.53, and exceeds the suggested logical criterion of an SNR. The Au\/Ag\/Au\/CS\u2013GO SPR sensor also exhibits excellent repeatability in Pb2+ due to the strong bond between its functional groups and this cation. The adsorption data of Pb2+ and Hg2+ on the CS\u2013GO sensor fits well with the Langmuir isotherm model where the affinity constant, K, of Pb2+ and Hg2+ ions is computed. The affinity of Pb2+ ions to the Au\/Ag\/Au\/CS\u2013GO sensor is significantly higher than that of Hg2+ based on the value of K, 7 \u00d7 105 M\u22121 and 4 \u00d7 105 M\u22121, respectively. The higher shift in SPR angles due to Pb2+ and Hg2+ compared to Cr3+, Cu2+ and Zn2+ ions also reveals the greater affinity of the CS\u2013GO SPR sensor to them, thus supporting the rationale for obtaining K for these two heavy metals. This study provides a better understanding on the sensing performance of such sensors in detecting heavy metal ions.<\/jats:p>","DOI":"10.3390\/s17102277","type":"journal-article","created":{"date-parts":[[2017,10,6]],"date-time":"2017-10-06T10:56:34Z","timestamp":1507287394000},"page":"2277","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":66,"title":["Binding Affinity of a Highly Sensitive Au\/Ag\/Au\/Chitosan-Graphene Oxide Sensor Based on Direct Detection of Pb2+ and Hg2+ Ions"],"prefix":"10.3390","volume":"17","author":[{"given":"Nur","family":"Kamaruddin","sequence":"first","affiliation":[{"name":"Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia"}]},{"given":"Ahmad Ashrif","family":"Bakar","sequence":"additional","affiliation":[{"name":"Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia"}]},{"given":"Nadhratun","family":"Mobarak","sequence":"additional","affiliation":[{"name":"School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia"}]},{"given":"Mohd Saiful","family":"Zan","sequence":"additional","affiliation":[{"name":"Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia"}]},{"given":"Norhana","family":"Arsad","sequence":"additional","affiliation":[{"name":"Department of Electric, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia"}]}],"member":"1968","published-online":{"date-parts":[[2017,10,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"572","DOI":"10.1016\/S1367-5931(00)00251-9","article-title":"Surface plasmon resonance: Towards an understanding of the mechanisms of biological molecular recognition","volume":"5","author":"McDonnell","year":"2001","journal-title":"Curr. Opin. Chem. Biol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"20120835","DOI":"10.1098\/rsif.2012.0835","article-title":"On the binding affinity of macromolecular interactions: Daring to ask why proteins interact","volume":"10","author":"Kastritis","year":"2013","journal-title":"J. R. Soc. Interface"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"721","DOI":"10.3390\/s130100721","article-title":"Performance comparison of two sensors based on surface plasmon resonance in a plastic optical fiber","volume":"13","author":"Cennamo","year":"2013","journal-title":"Sensors"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"864","DOI":"10.1016\/j.bios.2004.03.026","article-title":"Immobilization of metallothionein as a sensitive biosensor chip for the detection of metal ions by surface plasmon resonance","volume":"20","author":"Wu","year":"2004","journal-title":"Biosens. Bioelectron."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"6721","DOI":"10.1021\/la8005772","article-title":"Determination of the adsorption free energy for peptide-surface interactions by spr spectroscopy","volume":"24","author":"Wei","year":"2008","journal-title":"Langmuir"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/S0958-1669(05)80072-2","article-title":"Determination of kinetic rate and equilibrium binding constants for macromolecular interactions: A critique of the surface plasmon resonance literature","volume":"5","year":"1994","journal-title":"Curr. Opin. Biotechnol."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"De Mol, N.J., and Fischer, M.J. (2008). Kinetic and thermodynamic analysis of ligand-receptor interactions: Spr applications in drug development. Handbook of Surface Plasmon Resonance, Royal Society of Chemistry.","DOI":"10.1039\/9781847558220-00123"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1016\/j.snb.2006.07.033","article-title":"Detection of arsenic in groundwater using a surface plasmon resonance sensor","volume":"123","author":"Forzani","year":"2007","journal-title":"Sens. Actuators B Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1257","DOI":"10.1021\/es049234z","article-title":"Detection of heavy metal ions in drinking water using a high-resolution differential surface plasmon resonance sensor","volume":"39","author":"Forzani","year":"2004","journal-title":"Environ. Sci. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.bios.2014.01.056","article-title":"Detection of copper ions in drinking water using the competitive adsorption of proteins","volume":"57","author":"Wang","year":"2014","journal-title":"Biosens. Bioelectron."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"784","DOI":"10.1016\/j.snb.2006.10.019","article-title":"Studies of metal ion binding by apo-metallothioneins attached onto preformed self-assembled monolayers using a highly sensitive surface plasmon resonance spectrometer","volume":"123","author":"Zhang","year":"2007","journal-title":"Sens. Actuators B Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1374","DOI":"10.1021\/ed074p1374","article-title":"What is a \u201cheavy metal\u201d?","volume":"74","author":"Hawkes","year":"1997","journal-title":"J. Chem. Educ."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1007\/s10311-010-0297-8","article-title":"Heavy metals, occurrence and toxicity for plants: A review","volume":"8","author":"Nagajyoti","year":"2010","journal-title":"Environ. Chem. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"306","DOI":"10.1016\/j.jiec.2016.03.037","article-title":"Combination of dispersive liquid\u2013liquid microextraction and multivariate optimization for separation-enrichment of traces lead by flame atomic absorption spectrometry","volume":"37","author":"Habila","year":"2016","journal-title":"J. Ind. Eng. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Taylor, H.E. (2001). Inductively Coupled Plasma-Mass Spectrometry: Practices and Techniques, Academic Press.","DOI":"10.1016\/B978-012683865-7\/50006-5"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.aca.2016.02.027","article-title":"A high-throughput solid-phase extraction microchip combined with inductively coupled plasma-mass spectrometry for rapid determination of trace heavy metals in natural water","volume":"916","author":"Shih","year":"2016","journal-title":"Anal. Chim. Acta"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"369","DOI":"10.1016\/j.sab.2004.11.002","article-title":"Multielement determination of heavy metals in water samples by continuous powder introduction microwave-induced plasma atomic emission spectrometry after preconcentration on activated carbon","volume":"60","author":"Jankowski","year":"2005","journal-title":"Spectrochim. Acta Part B At. Spectrosc."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.microc.2014.07.012","article-title":"Fast ultrasound-assisted treatment of inorganic fertilizers for mercury determination by atomic absorption spectrometry and microwave-induced plasma spectrometry with the aid of the cold-vapor technique","volume":"118","author":"Lima","year":"2015","journal-title":"Microchem. J."},{"key":"ref_19","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_20","doi-asserted-by":"crossref","first-page":"662","DOI":"10.1021\/ol303499v","article-title":"Colorimetric Hg2+ sensing in water: From molecules toward low-cost solid devices","volume":"15","author":"Ermakova","year":"2013","journal-title":"Org. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1016\/j.snb.2010.09.014","article-title":"Monodispersed au nanoparticles decorated graphene as an enhanced sensing platform for ultrasensitive stripping voltammetric detection of mercury(ii)","volume":"150","author":"Gong","year":"2010","journal-title":"Sens. Actuators B Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"176","DOI":"10.1016\/j.compag.2016.02.017","article-title":"On-site detection of heavy metals in agriculture land by a disposable sensor based virtual instrument","volume":"123","author":"Wang","year":"2016","journal-title":"Comput. Electron. Agric."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Mart\u00edn-Yerga, D., and Costa-Garc\u00eda, A. (2017). Recent advances in the electrochemical detection of mercury. Curr. Opin. Electrochem.","DOI":"10.1016\/j.coelec.2017.06.012"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"555","DOI":"10.1007\/s00604-013-0959-x","article-title":"A glassy carbon electrode modified with graphene, gold nanoparticles and chitosan for ultrasensitive determination of lead (ii)","volume":"180","author":"Lu","year":"2013","journal-title":"Microchim. Acta"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/j.foodchem.2015.07.042","article-title":"Simultaneously determination of trace Cd2+ and Pb2+ based on l-cysteine\/graphene modified glassy carbon electrode","volume":"192","author":"Zhou","year":"2016","journal-title":"Food Chem."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"426","DOI":"10.1016\/j.snb.2013.01.040","article-title":"Graphene based fiber optic surface plasmon resonance for bio-chemical sensor applications","volume":"187","author":"Kim","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2437","DOI":"10.1109\/LPT.2015.2467189","article-title":"Graphene-based conducting metal oxide coated d-shaped optical fiber spr sensor","volume":"27","author":"Patnaik","year":"2015","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"11753","DOI":"10.1002\/ange.201206804","article-title":"Surface plasmon resonance chemical sensing on cell phones","volume":"124","author":"Preechaburana","year":"2012","journal-title":"Angew. Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"12864","DOI":"10.1038\/srep12864","article-title":"Surface plasmon resonance biosensor based on smart phone platforms","volume":"5","author":"Liu","year":"2015","journal-title":"Sci. Rep."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"673","DOI":"10.1039\/b717736d","article-title":"Thin chitosan films as a platform for spr sensing of ferric ions","volume":"133","author":"McIlwee","year":"2008","journal-title":"Analyst"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1007\/s10043-011-0064-5","article-title":"Surface plasmon resonance detection of copper corrosion in biodiesel using polypyrrole-chitosan layer sensor","volume":"18","author":"Sadrolhosseini","year":"2011","journal-title":"Opt. Rev."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"284","DOI":"10.1080\/00914037.2012.664209","article-title":"Application of polypyrrole-chitosan layer for detection of Zn (II) and Ni (II) in aqueous solutions using surface plasmon resonance","volume":"62","author":"Sadrolhosseini","year":"2013","journal-title":"Int. J. Polym. Mater. Polym. Biomater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.carbpol.2003.08.005","article-title":"Metal complexation by chitosan and its derivatives: A review","volume":"55","author":"Varma","year":"2004","journal-title":"Carbohydr. Polym."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Abdi, M.M., Abdullah, L.C., Sadrolhosseini, A.R., Mat Yunus, W.M., Moksin, M.M., and Tahir, P.M. (2011). Surface plasmon resonance sensing detection of mercury and lead ions based on conducting polymer composite. PLoS ONE, 6.","DOI":"10.1371\/journal.pone.0024578"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"453","DOI":"10.4015\/S101623721250041X","article-title":"A reversible optical sensor based on chitosan film for the selective detection of copper ions","volume":"24","author":"Lin","year":"2012","journal-title":"Biomed. Eng. Appl. Basis Commun."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Chiu, N.-F., Huang, T.-Y., and Lai, H.-C. (2013). Graphene oxide based surface plasmon resonance. Biosensors.","DOI":"10.5772\/56221"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"703","DOI":"10.1016\/j.biortech.2012.02.067","article-title":"Preparation of novel magnetic chitosan\/graphene oxide composite as effective adsorbents toward methylene blue","volume":"114","author":"Fan","year":"2012","journal-title":"Bioresour. Technol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1435","DOI":"10.1007\/s00216-012-6624-0","article-title":"Recent advances in the development of graphene-based surface plasmon resonance (spr) interfaces","volume":"405","author":"Szunerits","year":"2013","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1002\/jctb.4220","article-title":"Graphene oxide and its application as an adsorbent for wastewater treatment","volume":"89","author":"Kyzas","year":"2014","journal-title":"J. Chem. Technol. Biotechnol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"459","DOI":"10.1016\/j.snb.2014.01.074","article-title":"Highly sensitive spr response of au\/chitosan\/graphene oxide nanostructured thin films toward Pb (II) ions","volume":"195","author":"Lokman","year":"2014","journal-title":"Sens. Actuators B Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.apsusc.2015.11.099","article-title":"Enhancement of chitosan-graphene oxide spr sensor with a multi-metallic layers of au\u2013ag\u2013au nanostructure for lead (ii) ion detection","volume":"361","author":"Kamaruddin","year":"2016","journal-title":"Appl. Surf. Sci."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"United States Environmental Protection Agency (2005). Introduction to United States Environmental Protection Agency Hazardous Waste Identification (40 cfr parts 261).","DOI":"10.2175\/193864705783867675"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"911","DOI":"10.3390\/ma6030911","article-title":"Covalently bonded chitosan on graphene oxide via redox reaction","volume":"6","author":"Icaza","year":"2013","journal-title":"Materials"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1453","DOI":"10.1021\/bm1000235","article-title":"Synthesis and characterization of starch citrate\u2013chitosan foam with superior water and saline absorbance properties","volume":"11","author":"Salam","year":"2010","journal-title":"Biomacromolecules"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1698","DOI":"10.1016\/j.jece.2016.02.035","article-title":"Chitosan-functionalized graphene oxide: A novel adsorbent an efficient adsorption of arsenic from aqueous solution","volume":"4","author":"Kumar","year":"2016","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"527","DOI":"10.3390\/polym7030527","article-title":"Study on the effect of silanization and improvement in the tensile behavior of graphene-chitosan-composite","volume":"7","author":"Kim","year":"2015","journal-title":"Polymers"},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Yan, T., Zhang, H., Huang, D., Feng, S., Fujita, M., and Gao, X.-D. (2017). Chitosan-functionalized graphene oxide as a potential immunoadjuvant. Nanomaterials, 7.","DOI":"10.3390\/nano7030059"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"287","DOI":"10.1016\/j.snb.2012.03.070","article-title":"Surface plasmon resonance optical sensor for detection of Pb2+ based on immobilized p-tert-butylcalix[4]arene-tetrakis in chitosan thin film as an active layer","volume":"171\u2013172","author":"Fen","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/j.ijleo.2011.11.035","article-title":"Analysis of Pb (ii) ion sensing by crosslinked chitosan thin film using surface plasmon resonance spectroscopy","volume":"124","author":"Fen","year":"2013","journal-title":"Opt.-Int. J. Light Electron. Opt."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/j.talanta.2016.05.053","article-title":"Differential pulse anodic stripping voltammetry for detection of as (iii) by chitosan-fe (oh) 3 modified glassy carbon electrode: A new approach towards speciation of arsenic","volume":"158","author":"Saha","year":"2016","journal-title":"Talanta"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"589","DOI":"10.1016\/j.snb.2012.11.094","article-title":"Fabrication and characterization of a surface plasmon resonance based fiber optic sensor using gel entrapment technique for the detection of low glucose concentration","volume":"177","author":"Singh","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1088\/0335-7368\/6\/5\/304","article-title":"Leaky waves in planar optical waveguides","volume":"6","author":"Tamir","year":"1975","journal-title":"Nouvelle Revue d'Optique"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1109\/PROC.1963.1758","article-title":"The spectrum of electromagnetic waves guided by a plasma layer","volume":"51","author":"Tamir","year":"1963","journal-title":"Proc. IEEE"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"372","DOI":"10.1063\/1.1775294","article-title":"Large positive and negative lateral optical beam displacements due to surface plasmon resonance","volume":"85","author":"Yin","year":"2004","journal-title":"Appl. Phys. Lett."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"4723","DOI":"10.1364\/OE.22.004723","article-title":"How to avoid a negative shift in reflection-type surface plasmon resonance biosensors with metallic nanostructures","volume":"22","author":"Kim","year":"2014","journal-title":"Opt. Expr."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"62","DOI":"10.3390\/s20200062","article-title":"Bimetallic layers increase sensitivity of affinity sensors based on surface plasmon resonance","volume":"2","author":"Zynio","year":"2002","journal-title":"Sensors"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"11390","DOI":"10.3390\/s101211390","article-title":"Resolution enhancement in surface plasmon resonance sensor based on waveguide coupled mode by combining a bimetallic approach","volume":"10","author":"Lee","year":"2010","journal-title":"Sensors"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"8352","DOI":"10.1002\/anie.201202318","article-title":"Chemical interface damping in single gold nanorods and its near elimination by tip-specific functionalization","volume":"51","author":"Zijlstra","year":"2012","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"1430","DOI":"10.1021\/ac402126k","article-title":"Stable and sensitive silver surface plasmon resonance imaging sensor using trilayered metallic structures","volume":"86","author":"Wang","year":"2013","journal-title":"Anal. Chem."},{"key":"ref_60","doi-asserted-by":"crossref","unstructured":"Raether, H. (1988). Surface Plasmons on Smooth Surfaces, Springer.","DOI":"10.1007\/BFb0048317"},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"064906","DOI":"10.1063\/1.3562142","article-title":"Enhanced surface plasmon polariton propagation length using a buried metal grating","volume":"109","author":"Jose","year":"2011","journal-title":"J. Appl. Phys."},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1002\/app.26704","article-title":"Removal of Cd(ii), Hg(ii), and Pb(ii) ions from aqueous solution using p(hema\/chitosan) membranes","volume":"106","author":"Bayramoglu","year":"2007","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"3533","DOI":"10.1021\/ja00905a001","article-title":"Hard and soft acids and bases","volume":"85","author":"Pearson","year":"1963","journal-title":"J. Am. Chem. Soc."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"7512","DOI":"10.1021\/ja00364a005","article-title":"Absolute hardness: Companion parameter to absolute electronegativity","volume":"105","author":"Parr","year":"1983","journal-title":"J. Am. Chem. Soc."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"369","DOI":"10.1007\/BF02708340","article-title":"Chemical hardness and density functional theory","volume":"117","author":"Pearson","year":"2005","journal-title":"J. Chem. Sci."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"523","DOI":"10.1016\/j.colsurfb.2012.11.006","article-title":"Highly selective adsorption of lead ions by water-dispersible magnetic chitosan\/graphene oxide composites","volume":"103","author":"Fan","year":"2013","journal-title":"Colloids Surf. B Biointerfaces"},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"59","DOI":"10.5185\/amlett.2015.7592","article-title":"Synthesis and characterization of graphite doped chitosan composite for batch adsorption of lead (ii) ions from aqueous solution","volume":"6","author":"Gedam","year":"2015","journal-title":"Adv. Mater. Lett."},{"key":"ref_68","doi-asserted-by":"crossref","unstructured":"Weiner, E.R. (2012). Applications of Environmental Aquatic Chemistry: A Practical Guide, CRC Press.","DOI":"10.1201\/b12963"},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"1118","DOI":"10.1109\/JSEN.2007.897946","article-title":"Fiber-optic sensors based on surface plasmon resonance: A comprehensive review","volume":"7","author":"Sharma","year":"2007","journal-title":"Sens. J. IEEE"},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"093111","DOI":"10.1063\/1.2721779","article-title":"On the performance of different bimetallic combinations in surface plasmon resonance based fiber optic sensors","volume":"101","author":"Sharma","year":"2007","journal-title":"J. Appl. Phys."},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"5493","DOI":"10.1002\/pmic.200600216","article-title":"Label-free detection methods for protein microarrays","volume":"6","author":"Yu","year":"2006","journal-title":"Proteomics"},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"4427","DOI":"10.1021\/ac0621773","article-title":"Detection of heavy metal ions in water by high-resolution surface plasmon resonance spectroscopy combined with anodic stripping voltammetry","volume":"79","author":"Wang","year":"2007","journal-title":"Anal. Chem."},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Homola, J.R. (2006). SURFACE Plasmon Resonance Based Sensors, Springer Science and Business Media.","DOI":"10.1007\/b100321"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/10\/2277\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:46:39Z","timestamp":1760208399000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/10\/2277"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,10,6]]},"references-count":73,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2017,10]]}},"alternative-id":["s17102277"],"URL":"https:\/\/doi.org\/10.3390\/s17102277","relation":{"is-referenced-by":[{"id-type":"doi","id":"10.1007\/s11220-025-00582-w","asserted-by":"object"}]},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,10,6]]}}}