Name: Creating Topographical and NanoIR Images of the Multipolymer Sample
Uploaded: 2023-06-23T14:55:00
Description: Watch this Scientific Journal Video about Creating Topographical and NanoIR Images of the Multipolymer Sample at JoVE.com

creating topographical and nanoir images of the multipolymer sample

Utforska flerfasiga polymera system med infraröd spektroskopi i nanoskala

Atomic force microscopy (AFM) has become essential to image and characterize the morphology of a wide variety of samples with nanoscale resolution1,2,3. By measuring the deflection of an AFM cantilever resulting from the interaction of the sharp tip with the sample surface, nanoscale functional imaging protocols for local stiffness measurements and tip-sample adhesion have been developed4,5. For soft condensed matter and polymer analysis, AFM measurements exploring the nanomechanical and nanochemical properties of local domains are highly sought after6,7,8. Before the emergence of nanoscale infrared (nanoIR) spectroscopy, AFM tips were chemically modified to assess the presence of different domains from the AFM force curve and deduct the nature of the tip-sample interaction. For instance, this approach was used to unveil the transformation of microdomains of poly(tert-butyl acrylate) at the surface of cyclohexane-treated polystyrene-block-poly(tert-butyl acrylate)block copolymer thin films at the sub 50 nm level9.
The combination of infrared (IR) light with AFM has had a significant impact on the field of polymer science6. Conventional IR spectroscopy is a widely used technique for studying the chemical structure of polymeric materials10,11, but it fails to provide information on individual phases and interphase behavior, as the regions are too small compared to the size of the IR beam used to probe the sample. The problem holds with IR microspectroscopy, as it is restricted by the optical diffraction limit6. Such measurements average the contributions of the entire region excited by the IR light; the signals resulting from the presence of nanoscale phases inside the probed region either exhibit complex fingerprints that should be deconvoluted during post-processing or are lost due to a signal level below the detectable level. Hence, it is essential to develop tools capable of nanoscale spatial resolution and high IR sensitivity to explore nanoscale chemical features in complex media.
Schemes to achieve nanoIR spectroscopy have been developed, first using a metallic AFM tip as a nanoantenna12,13, and more recently exploiting the AFM cantilever&#39;s ability to monitor changes in the photothermal expansion incurred during IR illumination of the sample12,14,15. The latter uses a pulsed, tunable IR light source tuned to an absorption band of the material probed, which causes the sample to absorb radiation and undergo photothermal expansion. This approach is well-suited for organic and polymeric materials. The pulsed excitation makes the effect detectable by the AFM cantilever in contact with the sample surface in the form of an oscillation. The amplitude of one of the contact resonances of the system observed in the frequency spectrum is then monitored as a function of illumination wavelength, which constitutes the nanoIR absorption spectrum of the material beneath the AFM tip15. The spatial resolution of nanoIR imaging and spectroscopy is limited by various effects of the photothermal expansion of the material. It has been evaluated that photothermal nanoIR spectroscopy using contact mode AFM can acquire the vibrational absorption spectra properties of materials with sub 50 nm scale spatial resolution14, with recent work demonstrating the detection of monomers and dimers of &#945;-synuclein16,17. However, quantitative studies of the performance of nanoIR measurements on heterogeneous polymeric materials assembled in various configurations, such as the case of absorbers of finite dimensions embedded in the volume of various polymeric films, remain limited.
This article aims to create a polymeric assembly with an embedded feature of a known dimension to evaluate the sensitivity of photothermal expansion and spatial resolution of nanoIR during surface analysis. The protocol covers the preparation of a polyvinyl alcohol (PVA) polymer thin film on a silicon substrate and the placement of a three-dimensional polystyrene (PS) bead onto or embedded in the PVA film, which constitutes the formation of the model system. NanoIR imaging and spectroscopy measurements are described in the context of evaluating the signals generated by the same PS bead positioned on or beneath the PVA film. The influence of the bead position on the nanoIR signals is evaluated. Methods to assess the spatial footprint of the bead in the nanoIR map are discussed, and the effects of several parameters are considered.

Författare i fokus: Framsteg inom infraröd spektroskopi i nanoskala för att utforska flerfasiga polymera system  

Framsteg inom infraröd spektroskopi i nanoskala för att utforska flerfasiga polymera system

Our group focuses on advancing the field of nanoscale functional imaging and spectroscopy to study complex systems with an emphasis on nanoscale infrared spectroscopy. Our research aims to develop methods that allows us to make sense of the behavior of heterogeneous systems by studying their nanoscale properties. Understanding the role of actuations at different frequencies to extract information about the sample is essential.As this is complicated, developing samples that can be modeled with physics simulation packages is also important. A nanoscale infrared spectroscopy determining the penetration depth of the measurement and understanding how subsurface features affect the signal detected by the AFM tip is very important. This protocol proposes a simple approach to create a model system that enables quantifying the penetration depth of nanoscale infrared spectroscopy, and the effect of JUUL heating on the sample response involved in the measurement of multi-phase polymer materials.Our team will continue to focus on developing new ideas to improve nanoscale infrared spectroscopy and other nanoscale functional tools to explore real-life systems at a small scale.

Watch this Scientific Journal Video about Creating Topographical and NanoIR Images of the Multipolymer Sample at JoVE.com

Creating Topographical and NanoIR Images of the Multipolymer Sample  

Skapa topografiska och nanoIR-bilder av multipolymerprovet

För NanoIR-mätningar, placera atomkraftsmikroskopet, eller AFM, spetsen på den egenskap av intresse som identifierats från topografibilden. Välj stämgaffelikonen i NanoIR-kontrollpanelen för att bestämma kontaktresonansfrekvenserna för konsolen. Ställ sedan in ett belysningsvågnummer för att excitera fototermisk expansion i materialet.Ställ sedan in ett intervall av laserpulsfrekvens för att svepa och ställ in arbetscykeln för NanoIR-lasern. Välj hämta i fönstret för laserpulsinställning. Placera markörfältet på toppen för att välja den andra kontaktresonansen för spetsen sample system för NanoIR-mätningar.Klicka på den optimerade knappen för att rikta in mitten av IR-laserns brännzon med positionen för den utskjutande spetsen. Skaffa IR-laserbelysningsbakgrund. Välj vågnummerområde, stegstorlek och antal medelvärden för NanoIR-spektrumet.Utför sedan en bakgrundskorrigering av spektra genom att dividera den fototermiska amplituden med den dämpade bakgrunden. Aktivera faslåst slinga, eller PLL, automatisk inställning i laserpulsinställningsfönstret. Justera sedan den högsta och lägsta frekvensen för att skapa ett svepområde centrerat vid det andra resonansläget i den allmänna kontrollpanelen.Klicka på noll i PLL-kontrollpanelen och klicka sedan på okej i laserpulsinställningsfönstret. Aktivera IR-avbildning genom att markera kryssrutan för IR-avbildning aktiverad i NanoIR-kontrollpanelen. I bildvyn kontrollpanel väljer du höjd, amplitud två och fas två för att få de topografiska och kemiska bilderna av provet.Ställ sedan in förvärvsriktningen för att spåra eller spåra igen. Välj skanningsikonen på AFM-skanningskontrollpanelen. Välj sedan ikonen nu eller slutet av bildrutan på kontrollpanelen för att spara bilden.För att exportera data, högerklicka på bilden eller spektrumfilnamnen i datalistorna. Välj exportera och välj sedan det filformat som ska exporteras. Spara slutligen filen i önskad datormapp.NanoIR-spektrumet för polystyren gav två IR-band som motsvarade sträckningsläget för fenyldelen vid 1 600 vågtal och en delmängd av ringen som sträckte sig vid 1 730 vågtal. NanoIR-spektrumet för PVA uppvisade bättre överensstämmelse med FDIR-spektrumet, med det dominerande absorptionsbandet centrerat vid 1 730 vågnummer. NanoIR-spektra användes för att välja belysningsvågsnummer för kemisk avbildning av polystyrenpärlan som deponerats på ytan av PVA och av polystyrenpärlan belagd med PVA.Därefter samlades spektra in ovanpå en polystyrenpärla täckt med PVA vid olika laserstyrkor. Polystyrensignalen vid 1 600 vågtal var signifikant lägre än PVA-signalen vid 1 750 vågtal. Det noterades dock att en ökning av lasereffekten ledde till ett högre förhållande.

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Engineering

Creating Topographical and NanoIR Images of the Multipolymer Sample

Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition ...