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

Explorando sistemas poliméricos multifásicos por espectroscopia de infravermelho em 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 em destaque: Avanços na espectroscopia infravermelha em nanoescala para explorar sistemas poliméricos multifásicos  

Avanços em Espectroscopia de Infravermelho em 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  

Criação de imagens topográficas e nanoIR da amostra multipolímero

Para medições de NanoIR, posicione o microscópio de força atômica, ou AFM, na ponta da característica de interesse identificada a partir da imagem de topografia. Selecione o ícone do diapasão no painel de controle NanoIR para determinar as frequências de ressonância de contato do cantilever. Em seguida, defina um número de onda de iluminação para excitar a expansão fototérmica no material.Em seguida, defina uma faixa de frequência de pulso de laser para varrer e definir o ciclo de trabalho do laser NanoIR. Selecione adquirir dentro da janela de ajuste de pulso laser. Posicione a barra do marcador no pico para selecionar a ressonância de segundo contato do sistema de amostra de ponta para medições de NanoIR.Clique no botão otimizado para alinhar o centro da região focal do laser IR com a posição da ponta do cantilever. Adquira o fundo de iluminação a laser IR. Selecione o intervalo de número de onda, o tamanho do passo e o número de médias para o espectro NanoIR.Em seguida, realize uma correção de fundo dos espectros dividindo a amplitude fototérmica pelo fundo atenuado. Habilite o loop bloqueado de fase, ou PLL, o ajuste automático na janela de ajuste do pulso laser. Em seguida, ajuste a frequência máxima e mínima para criar uma faixa de varredura centralizada no segundo modo de ressonância no painel de controle geral.Clique em zero no painel de controle PLL e, em seguida, clique em OK na janela de ajuste de pulso laser. Habilite a imagem IR marcando a caixa de seleção da imagem IR habilitada no painel de controle NanoIR. No painel de controle de visualização de imagens, escolha altura, amplitude dois e fase dois para adquirir as imagens topográficas e químicas da amostra.Em seguida, defina a direção de aquisição para rastrear ou retraçar. Selecione o ícone de digitalização no painel de controle de verificação AFM. Em seguida, selecione o ícone agora ou fim do quadro no painel de controle de captura para salvar a imagem.Para exportar os dados, clique com o botão direito do mouse nos nomes dos arquivos de imagem ou espectro dentro das listas de dados. Selecione exportar e, em seguida, escolha o formato de arquivo a ser exportado. Finalmente, salve o arquivo na pasta do computador desejado.O espectro NanoIR do poliestireno produziu duas bandas IR correspondentes ao modo de estiramento da fração fenil em 1.600 número de onda e um subconjunto do anel esticando em 1.730 número de onda. O espectro NanoIR do PVA exibiu melhor concordância com o espectro FDIR, com a banda de absorção predominante centrada no número de 1.730 ondas. Os espectros NanoIR foram usados para selecionar os números de onda de iluminação para imagens químicas do cordão de poliestireno depositado na superfície do PVA e do cordão de poliestireno revestido com PVA.Em seguida, os espectros foram coletados em cima de um grânulo de poliestireno coberto com PVA em diferentes potências do laser. O sinal de poliestireno em 1.600 número de onda foi significativamente menor do que o de PVA em 1.750 número de onda. No entanto, notou-se que o aumento da potência do laser levou a uma maior relação.

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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 ...