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

Exploración de sistemas poliméricos multifásicos mediante espectroscopía infrarroja a nanoescala

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.

Autor destacado: Avances en espectroscopia infrarroja a nanoescala para explorar sistemas poliméricos multifásicos  

Avances en espectroscopía infrarroja a nanoescala para explorar sistemas poliméricos multifásicos

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  

Creación de imágenes topográficas y nanoIR de la muestra multipolímero

Para las mediciones de NanoIR, coloque la punta del microscopio de fuerza atómica, o AFM, en la característica de interés identificada a partir de la imagen topográfica. Seleccione el icono del diapasón en el panel de control NanoIR para determinar las frecuencias de resonancia de contacto del voladizo. A continuación, establezca un número de onda de iluminación para excitar la expansión fototérmica en el material.A continuación, establezca un rango de frecuencia de pulso láser para barrer y establezca el ciclo de trabajo del láser NanoIR. Seleccione adquirir dentro de la ventana de sintonización de pulsos láser. Coloque la barra de marcador en el pico para seleccionar la resonancia de segundo contacto del sistema de muestras de punta para las mediciones de NanoIR.Haga clic en el botón optimizado para alinear el centro de la región focal del láser IR con la posición de la punta en voladizo. Adquiera un fondo de iluminación láser IR. Seleccione el rango de números de onda, el tamaño de paso y el número de promedios para el espectro NanoIR.A continuación, realice una corrección de fondo de los espectros dividiendo la amplitud fototérmica por el fondo atenuado. Habilite el bucle de bloqueo de fase, o PLL, en la ventana de sintonización de pulso láser. A continuación, ajuste la frecuencia máxima y mínima para crear un rango de barrido centrado en el segundo modo de resonancia en el panel de control general.Haga clic en cero en el panel de control PLL y luego haga clic en Aceptar en la ventana de sintonización de pulso láser. Habilite la creación de imágenes IR seleccionando la casilla de verificación de Imágenes IR habilitadas en el panel de control de NanoIR. En el panel de control de la vista de imágenes, elija la altura, la amplitud dos y la fase dos para adquirir las imágenes topográficas y químicas de la muestra.A continuación, establezca la dirección de adquisición en trazar o volver a trazar. Seleccione el icono de escaneo en el panel de control de escaneo de AFM. A continuación, seleccione el icono ahora o fin de fotograma en el panel de control de captura para guardar la imagen.Para exportar los datos, haga clic con el botón derecho en los nombres de los archivos de imagen o espectro dentro de las listas de datos. Seleccione exportar y, a continuación, elija el formato de archivo que desea exportar. Finalmente, guarde el archivo en la carpeta de la computadora deseada.El espectro NanoIR del poliestireno produjo dos bandas IR correspondientes al modo de estiramiento de la fracción de fenilo con un número de onda de 1.600 y un subconjunto del anillo que se estira con un número de onda de 1.730. El espectro NanoIR del PVA mostró una mejor concordancia con el espectro FDIR, con la banda de absorción predominante centrada en el número de onda 1, 730. Los espectros NanoIR se utilizaron para seleccionar los números de onda de iluminación para la obtención de imágenes químicas de la perla de poliestireno depositada en la superficie del PVA y de la perla de poliestireno recubierta con PVA.A continuación, se recogieron espectros sobre una perla de poliestireno cubierta con PVA a diferentes potencias láser. La señal de poliestireno con un número de onda de 1.600 fue significativamente menor que la del PVA con un número de onda de 1.750. Sin embargo, se observó que el aumento de la potencia del láser conducía a una mayor proporción.

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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 ...