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

Utforske flerfasede polymere systemer ved infrarød 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.

Forfatter Spotlight: Fremskritt innen infrarød spektroskopi i nanoskala for å utforske flerfasede polymere systemer  

Fremskritt i nanoskala infrarød spektroskopi for å utforske flerfasede polymere systemer

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  

Opprette topografiske og NanoIR-bilder av multipolymerprøven

For NanoIR-målinger, plasser atomkraftmikroskopet, eller AFM, tips om funksjonen av interesse identifisert fra topografibildet. Velg stemmegaffelikonet i NanoIR-kontrollpanelet for å bestemme kontaktresonansfrekvensene til utkrageren. Sett deretter et belysningsbølgenummer for å opphisse fototermisk ekspansjon i materialet.Deretter angir du et område med laserpulsfrekvens for å feie og stiller inn driftssyklusen til NanoIR-laseren. Velg hent i laserpulsinnstillingsvinduet. Plasser markørlinjen øverst for å velge den andre kontaktresonansen til spissprøvesystemet for NanoIR-målinger.Klikk på den optimaliserte knappen for å justere midten av IR-laserfokalområdet med posisjonen til utkragespissen. Skaff deg IR-laserbelysningsbakgrunn. Velg bølgetallområdet, trinnstørrelsen og antall gjennomsnitt for NanoIR-spekteret.Utfør deretter en bakgrunnskorreksjon av spektrene ved å dele den fototermiske amplituden med den dempede bakgrunnen. Aktiver faselåst sløyfe, eller PLL, automatisk justering i laserpulsjusteringsvinduet. Juster deretter maksimums- og minimumsfrekvensen for å lage et feieområde sentrert i den andre resonansmodusen i det generelle kontrollpanelet.Klikk på null i PLL-kontrollpanelet, og klikk deretter på ok i laserpulsinnstillingsvinduet. Aktiver IR-avbildning ved å merke av for IR-bildebehandling aktivert i NanoIR-kontrollpanelet. I kontrollpanelet for bildevisning velger du høyde, amplitude to og fase to for å skaffe de topografiske og kjemiske bildene av prøven.Sett deretter anskaffelsesretningen til å spore eller gå tilbake. Velg skanneikonet i kontrollpanelet for AFM-skanning. Velg deretter ikonet for nå eller slutten av rammen i kontrollpanelet for å lagre bildet.For å eksportere dataene, høyreklikk på bilde- eller spektrumfilnavnene i datalistene. Velg eksporter, og velg deretter filformatet du vil eksportere. Til slutt lagrer du filen i ønsket datamaskinmappe.NanoIR-spekteret av polystyren ga to IR-bånd som tilsvarer strekkmodusen til fenyldelen ved 1.600 bølgenummer og en delmengde av ringen som strekker seg ved 1.730 bølgenummer. NanoIR-spekteret av PVA viste bedre samsvar med FDIR-spekteret, med det dominerende absorpsjonsbåndet sentrert ved 1.730 bølgenummer. NanoIR-spektrene ble brukt til å velge belysningsbølgetallene for kjemisk avbildning av polystyrenperlen avsatt på overflaten av PVA og av polystyrenperlen belagt med PVA.Deretter ble spektra samlet på toppen av en polystyrenperle dekket med PVA ved forskjellige laserkrefter. Polystyrensignalet ved 1.600 bølgenummer var betydelig lavere enn PVA ved 1.750 bølgenummer. Det ble imidlertid bemerket at økning av lasereffekten førte til et høyere forhold.

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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 ...