Confocal Raman microscopy was applied to detect structural change within individual particles of low-density polyethylene (LDPE) following chemical and electrochemical processing steps that aimed to facilitate material decomposition. A high numerical aperture (NA) oil-immersion objective enabled depth-profiling through the near surface region (20 μm–40 μm) of irregularly shaped particles with an axial spatial resolution < 2 μm estimated from measurements of instrument detection efficiency profiles. Changes in vibrational bands sensitive to polyethylene crystallinity were evident following treatments and linked to the release of low molecular weight compounds present as additives and products of processing. Effects of processing were probed by monitoring the rise of Raman scattering intensity in vibrational modes associated with polyethylene chains in a zig-zag (trans) conformation near 1128 cm–1, 1294 cm–1, and 1418 cm–1, signaling chain clustering and development of organized, crystalline-like assemblies. Pristine LDPE particles displayed a uniform structure across the near surface region, while particles treated initially with chemical extractant and then further processed displayed increasingly enhanced crystallinity up to the maximum depth probed (40 μm). As a step toward measurements on ensembles of particles, least squares modeling was adapted to derive pure component spectra reflecting crystallinity change within spectral datasets. The work demonstrates high spatial resolution Raman depth-profiling for the characterization of processed polymers using a high NA immersion objective to overcome the limitations of air-objectives often used for confocal Raman microscopy.
GeyerR.JambeckJ.R.LawK.L.. “Production, Use, and Fate of All Plastics Ever Made”. Sci. Adv. 2017. 3(7): e1700782. https://doi.org/10.1126/sciadv.1700782
2.
BorrelleS.B.RingmaJ.LawK.L.MonnahanC.C., et al. “Predicted Growth in Plastic Waste Exceeds Efforts to Mitigate Plastic Pollution”. Science. 2020. 369(6510): 1515–1581. https://doi.org/10.1126/science.aba3656
3.
ElkhatibD.Oyanedel-CraverV.. “A Critical Review of Extraction and Identification Methods of Microplastics in Wastewater and Drinking Water”. Environ. Sci. Technol. 2020. 54(12): 7037–7049. https://doi.org/10.1021/acs.est.9b06672
4.
SchwafertsC.SogneV.WelzR.MeierF., et al. “Nanoplastic Analysis by Online Coupling of Raman Microscopy and Field-Flow Fractionation Enabled by Optical Tweezers”. Anal. Chem. 2020. 92(8): 5813–5820. https://doi.org/10.1021/acs.analchem.9b05336
5.
GillibertR.BalakrishnanG.DeshoulesQ.TardivelM., et al. “Raman Tweezers for Small Microplastics and Nanoplastics Identification in Seawater”. Environ. Sci. Technol. 2019. 53(15): 9003–9013. https://doi.org/10.1021/acs.est.9b03105
6.
WrightS.L.LevermoreJ.M.KellyF.J.. “Raman Spectral Imaging for the Detection of Inhalable Microplastics in Ambient Particulate Matter Samples”. Environ. Sci. Technol. 2019. 53(15): 8947–8956. https://doi.org/10.1021/acs.est.8b06663
7.
LevermoreJ.M.SmithT.E.L.KellyF.J.WrightS.L.. “Detection of Microplastics in Ambient Particulate Matter Using Raman Spectral Imaging and Chemometric Analysis”. Anal. Chem. 2020. 92(13): 8732–8740. https://doi.org/10.1021/acs.analchem.9b05445
8.
RahimzadehR.Ortega-RamosJ.HaqueZ.BotteG.G.. “Electrochemical Oxidation and Functionalization of Low-Density Polyethylene”. ChemElectroChem. 2023. 10(10): e202300021. https://doi.org/10.1002/celc.202300021
9.
EverallN.J.. “Confocal Raman Microscopy: Common Errors and Artefacts”. Analyst. 2010. 135(10): 2512–2522. https://doi.org/10.1039/c0an00371a
10.
FroudC.A.HaywardI.P.LavenJ.. “Advances in the Raman Depth Profiling of Polymer Laminates”. Appl. Spectrosc. 2003. 57(12): 1468–1474. https://doi.org/10.1366/000370203322640099
11.
de GrauwC.J.SijtsemaN.M.OttoC.GreveJ.. “Axial Resolution of Confocal Raman Microscopes: Gaussian Beam Theory and Practice”. J. Microscopy. 1997. 188(3): 273–279. https://doi.org/10.1046/j.1365-2818.1997.2620818.x
12.
BridgesT.HoulneM.HarrisJ.M.. “Spatially Resolved Analysis of Small Particles by Confocal Raman Microscopy: Depth Profiling and Optical Trapping”. Anal. Chem. 2004. 76(3): 576–584. https://doi.org/10.1021/ac034969s
13.
KorzeniewskiC.KittJ.P.BukolaS.CreagerS.E., et al. “Single Layer Graphene for Estimation of Axial Spatial Resolution in Confocal Raman Microscopy Depth Profiling”. Anal. Chem. 2019. 91(1): 1049–1055. https://doi.org/10.1021/acs.analchem.8b04390
14.
SaccoA.PortesiC.GiovannozziA.M.RossiA.M.. “Graphene Edge Method for Three-Dimensional Probing of Raman Microscopes Focal Volumes”. J. Raman Spectrosc. 2021. 52(10): 1671–1684. https://doi.org/10.1002/jrs.6187
15.
HuangS.-C.YeJ.-Z.ShenX.-R.ZhaoQ.-Q., et al. “Electrochemical Tip-Enhanced Raman Spectroscopy with Improved Sensitivity Enabled by a Water Immersion Objective”. Anal. Chem. 2019. 91(17): 11092−11097. 10.1021/acs.analchem.9b01701
16.
PengZ.HuguetP.DeabateS.MorinA.SutorA.K.. “Depth-Resolved Micro-Raman Spectroscopy of Tri-Layer PFSA Membrane for PEM Fuel Cells: How to Obtain Reliable Inner Water Contents”. J. Raman Spectrosc. 2013. 44(2): 321–328. https://doi.org/10.1002/jrs.4192
17.
DeabateS.HuguetP.MorinA.GebelG., et al. “Raman Microspectroscopy as a Useful Tool for In Situ and Operando Studies of Water Transport in Perfluorosulfonic Membranes for PEMFCs”. Fuel Cells. 2014. 14(5): 677–693. https://doi.org/10.1002/fuce.201300236
18.
BukolaS.BeardK.KorzeniewskiC.HarrisJ.M.CreagerS.E.. “Single-Layer Graphene Sandwiched Between Proton-Exchange Membranes for Selective Proton Transmission”. ACS Appl. Nano Mater. 2019. 2(2): 964–974. https://doi.org/10.1021/acsanm.8b02270
19.
BukolaS.LiangY.KorzeniewskiC.HarrisJ.CreagerS.E.. “Selective Proton/Deuteron Transport Through Nafion|Graphene|Nafion Sandwich Structures at High Current Density”. J. Am. Chem. Soc. 2018. 140(5): 1743–1752. https://doi.org/10.1021/jacs.7b10853
20.
BridgesT.E.UibelR.H.HarrisJ.M.. “Measuring Diffusion of Molecules into Individual Polymer Particles by Confocal Raman Microscopy”. Anal. Chem. 2006. 78(7): 2121–2129. https://doi.org/10.1021/ac052056n
21.
KittJ.P.HarrisJ.M.. “Confocal Raman Microscopy for in Situ Measurement of Octanol-Water Partitioning Within Pores of Individual C18-Functionalized Chromatographic Particles”. Anal. Chem. 2015. 87(10): 5340–5347. https://doi.org/10.1021/acs.analchem.5b00634
22.
BryceD.A.KittJ.P.HarrisJ.M.. “Confocal Raman Microscopy for Label-Free Detection of Protein–Ligand Binding at Nanopore-Supported Phospholipid Bilayers”. Anal. Chem. 2018. 90(19): 11509–11516. https://doi.org/10.1021/acs.analchem.8b02791
23.
MyresG.J.PetersonE.M.HarrisJ.M.. “Confocal Raman Microscopy Enables Label-Free, Quantitative, and Structurally Informative Detection of DNA Hybridization at Porous Silica Surfaces”. Anal. Chem. 2021. 93(22): 7978–7986. https://doi.org/10.1021/acs.analchem.1c00885
24.
MyresG.J.KittJ.P.HarrisJ.M.. “Inter-Leaflet Phospholipid Exchange Impacts the Ligand Density Available for Protein Binding at Supported Lipid Bilayers”. Langmuir. 2022. 38(22): 6967–6976. https://doi.org/10.1021/acs.langmuir.2c00526
25.
HarbinH.J.UnruhD.K.CasadonteD.J.KhatibS.J.. “Sonochemically Prepared Ni-Based Perovskites as Active and Stable Catalysts for Production of Cox-Free Hydrogen and Structured Carbon”. ACS Catal. 2023. 13(7): 4205–4220. https://doi.org/10.1021/acscatal.2c05672
26.
XuJ.KohM.MinteerS.D.KorzeniewskiC.. “In Situ Confocal Raman Microscopy of Redox Polymer Films on Bulk Electrode Supports”. ACS Meas. Sci. Au. 2023. 3(2): 127–133. https://doi.org/10.1021/acsmeasuresciau.2c00064
27.
KittJ.P.BryceD.A.HarrisJ.M.. “Spatial Filtering of a Diode Laser Beam for Confocal Raman Microscopy”. Appl. Spectrosc. 2015. 69(4): 513–517. https://doi.org/10.1366/14-07671
28.
WilliamsK.P.J.PittG.D.BatchelderD.N.KipB.J.. “Confocal Raman Microspectroscopy Using a Stigmatic Spectrograph and CCD Detector”. Appl. Spectrosc. 1994. 48(2): 232–235. https://doi.org/10.1366/0003702944028407
29.
WangY.McCreeryR.L.. “Evaluation of a Diode Laser/Charge Coupled Device Spectrometer for Near-Infrared Raman Spectroscopy”. Anal. Chem. 1989. 61(23): 2647–2651. https://doi.org/10.1021/ac00198a012
30.
FrylingM.A.FrankC.J.McCreeryR.L.. “Intensity Calibration and Sensitivity Comparisons for CCD/Raman Spectrometers”. Appl. Spectrosc. 1993. 47(12): 1965–1974. https://doi.org/10.1366/0003702934066226
31.
ChoquetteS.J.EtzE.S.HurstW.S.BlackburnD.H.LeighS.D.. “Relative Intensity Correction of Raman Spectrometers: NIST SRMs 2241 Through 2243 for 785 nm, 532 nm, and 488 nm/514.5 nm Excitation”. Appl. Spectrosc. 2007. 61(2): 117–129. https://doi.org/10.1366/000370207779947585
32.
BrandtN.N.OrovkoO.O.ChikishevA.Y.ParaschukO.D.. “Optimization of the Rolling-Circle Filter for Raman Background Subtraction”. Appl. Spectrosc. 2006. 60(3): 288–293. https://doi.org/10.1366/000370206776342553
33.
MalinowskiE.R.. Factor Analysis in Chemistry. New York: Wiley, 2002.
34.
BeattieJ.R.Esmonde-WhiteF.W.L.. “Exploration of Principal Component Analysis: Deriving Principal Component Analysis Visually Using Spectra”. Appl. Spectrosc. 2021. 75(4): 361–375. https://doi.org/10.1177/0003702820987847
35.
RiveraD.PetersonP.E.UibelR.H.HarrisJ.M.. “In Situ Adsorption Studies at Silica/Solution Interfaces by Attenuated Total Internal Reflection Fourier Transform Infrared Spectroscopy: Examination of Adsorption Models in Normal-Phase Liquid Chromatography”. Anal. Chem. 2000. 72(7): 1543–1554. https://doi.org/10.1021/ac990968h
36.
KorzeniewskiC.AdamsE.LiuD.. “Responses of Hydrophobic and Hydrophilic Groups in Nafion Differentiated by Least Squares Modeling of Infrared Spectra Recorded During Thin Film Hydration”. Appl. Spectrosc. 2008. 62(6): 634–639. https://doi.org/10.1366/000370208784658075
37.
KorzeniewskiC.PetersonE.M.KittJ.P.MinteerS.D.HarrisJ.M.. “Adapting Confocal Raman Microscopy for in Situ Studies of Redox Transformations at Electrode–Electrolyte Interfaces”. J. Electroanal. Chem. 2021. 896: 115207. 10.1016/j.jelechem.2021.115207
38.
SatoH.ShimoyamaM.KamiyaT.AmariT., et al. “Raman Spectra of High-Density, Low-Density, and Linear Low-Density Polyethylene Pellets and Prediction of Their Physical Properties by Multivariate Data Analysis”. J. Appl. Polym. Sci. 2002. 86(2): 443–448. https://doi.org/10.1002/app.10999
39.
OldakD.KaczmarekH.BuffeteauT.SourisseauC.. “Photo- and Bio-Degradation Processes in Polyethylene, Cellulose and Their Blends Studied by ATR-FTIR and Raman Spectroscopies”. J. Mater. Sci. 2005. 40: 4189–4198. https://doi.org/10.1007/s10853-005-2821-y
40.
SnyderR.G.HsuS.L.KrimmS.. “Vibrational Spectra in the C–H Stretching Region and the Structure of the Polymethylene Chain”. Spectrochim. Acta. 1978. 34(4): 395–406. https://doi.org/10.1016/0584-8539(78)80167-6
41.
HiejimaY.KidaT.TakedaK.IgarashiT.NittaK.. “Microscopic Structural Changes During Photodegradaation of Low-Density Polyethylene Detected by Raman Spectroscopy”. Polym. Degrad. Stab. 2018. 150: 67–72. https://doi.org/10.1016/j.polymdegradstab.2018.02.010
42.
KangB.R.KimS.B.SongH.A.LeeT.K.. “Accelerating the Biodegradation of High-Density Polyethylene (HDPE) Using Bjerkandera adusta TBB-03 and Lignocellulose Substrates”. Microorganisms. 2019. 7(9): 304. https://doi.org/10.3390/microorganisms7090304
43.
PriceG.J.. “Polymer Sonochemistry: Controlling the Structure and Properties of Macromolecules”. In: CrumL.A.MasonT.J.ReisseJ.L.SuslickK.S., editors. Sonochemistry and Sonoluminescence. Dordrecht, Netherlands: Kluwer Academic Publishers, 1999. Pp. 321–343. 10.1007/978-94-015-9215-4_25
44.
CasadonteD.J.McCouryJ.KorremulaB.. “Heterodyne I: Enhancing Sonochemical Efficiency Through Application of the Heterodyne Effect: An Initial Study”. Ultrason. Sonochem. 2019. 56: 143–149. https://doi.org/10.1016/j.ultsonch.2019.04.014
45.
RieszP.KondoT.. “Free Radical Formation Induced by Ultrasound and Its Biological Implications”. Free Radic. Biol. Med. 1992. 13(3): 247–270. https://doi.org/10.1016/0891-5849(92)90021-8
46.
PetrierC.JeunetA.LucheJ.L.ReverdyG.. “Unexpected Frequency Effects on the Rate of Oxidative Processes Induced by Ultrasound”. J. Am. Chem. Soc. 1992. 114(8): 3148–3150. https://doi.org/10.1021/ja00034a077
47.
CasadonteD.J.Jr.FloresM.PetrierC.. “The Use of Pulsed Ultrasound Technology to Improve Environmental Remediation: A Comparative Study”. Environ. Tech. 2005. 26(12): 1411–1416. https://doi.org/10.1080/09593332608618615
48.
CasadonteD.J.Jr.FloresM.PetrierC.. “Enhancing Sonochemical Degradation of Environmental Contaminants Using Power-Modulated Pulsed Ultrasound: An Initial Study”. Ultrason. Sonochem. 2005. 12(3): 147–152. https://doi.org/10.1016/j.ultsonch.2003.12.004
49.
XingX.ZhaoS.XuT.HuangL., et al. “Advances and Perspectives in Organic Sonosensitizers for Sonodynamic Therapy”. Coord. Chem. Rev. 2021. 445: 214087. 10.1016/j.ccr.2021.214087
50.
KoppelD.E.AxelrodD.SchlessingerJ.ElsonE.L.WebbW.W.. “Dynamics of Fluorescence Marker Concentration as a Probe of Mobility”. Biophys. J. 1976. 16(11): 1315–1329. https://doi.org/10.1016/S0006-3495(76)85776-1
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
