How can you use analytical techniques to characterize self-assembled monolayers (SAMs)?

fastest and cheaper would be contact angle but tells you very little of your monolayer, and whether it's actually a monolayer or not. Surely SAM's quality is influencing the CA

Contact angle method is the most reliable technique.It can easily characterize the SAM and its wettability.It is very popularly used in the fields where DAM is the part of methodology

SAM functional group identification by FTIR with grazing angle. You need to see which detector will be best - low noise or higher resolution. Try playing with the angle to choose the one that gives you more info- high intensity picks. SPM - or AFM for the molecules distribution, image wise. For conductivity imaging one can try TUNA. Contact angle changes can indicate the molecule presence, but not it's order on the substrate. It's a more averaging technique.

Contact angle analysis may be rapid way to analysis SAM coated surfaces, however I feel FE-SEM and X-RAY diffraction analysis to be more efficient and accurate ways to analyse monolayers.

Through contact angle we can know about 1. Chemical composition: Different functional groups on the SAM surface will interact with the liquid droplet differently, leading to variations in the contact angle. 2. Packing density: A well-packed SAM with closely packed molecules will generally exhibit a higher contact angle compared to a less densely packed SAM. 3. Orientation of the molecules: The tilt angle of the molecules within the SAM can affect the contact angle.

In the analysis of organic chain molecules attached to a metal surface, infrared reflection absorption spectroscopy (IRRAS) is commonly used to determine their orientation. Although obtaining the IR spectrum itself is relatively straightforward, the complexity arises in determining orientational parameters such as tilt and twist angles. This challenge is compounded by the need to use the bulk reference spectrum of the substance forming the SAMs.

Polarisation modulation-IIRAS (PM-IRRAS) is an FT-IR approach that can overcome issues concerning signal intensity and suppression by atmospheric interferences. At a high grazing angle, the intensity of the electric field of p-polarised IR light is enhanced, due to constructive interference. In contrast, the electric field of s-polarised light at this incident angle is practically cancelled, resulting in negligible interaction with the SAM. Thus, the reflected s-polarised light can provide the IR reflectance spectrum of the metal surface. By exploiting this simple selection rule for absorption of IR radiation at the surface, the spectrum of the molecular layer and the background can be obtained in a single measurement of the same sample.

This is a great and also tricky method. Because of extremely thin thickness a lot of SAMs give weak and unclear spectra. if the control measurement is not clean enough it changes completely the result. I saw a lot of misleading and wrong interpretations of SAMs IR spectra that resulted from poor backgrounds or too intense extrapolations from the plots that changed completely the face of the plot - like water traces signals were taken as peaks of SAM. In my opinion, it can be a good tool, but it requires very high level of understanding of the spectrology and the technique that the device operates. Clear understanding of limitation of each device, and, the best is to leave these measurements to a skilled person as a supervisor or an expert.

If SAMs are a monolayer on a metalic surface then Phase Modulation -IRRAS will measure the IR spectrum of molecule oriented perpendicular to the surface.

Characterizing self-assembled monolayers (SAMs) using infrared spectroscopy: 1-Perform infrared spectroscopy on the SAM sample. 2-Use an infrared spectrometer to obtain the absorption spectrum. 3-Analyze spectrum to identify functional groups and chemical bonds in the SAM. 4-Compare spectrum with references to determine composition and structure. 5-Quantify component abundance using peak intensities or area calculations. 6-Utilize techniques like ATR or RAIRS for reflective/opaque substrates. 7-Combine with XPS or SPM for complementary characterization.

Grazing incidence small angle X-ray scattering (GISAXS) can be used to characterize morphology of self assembled monolayer thin films. Atomic force microscopy (AFM) can also provide phase/orientation information.

X-ray Photoelectron Spectroscopy (XPS): ? Principle: Measures the binding energies of electrons ejected from atoms upon X-ray irradiation. ? Application: Determines elemental composition and chemical states, offering insights into SAM composition and surface functionality.

Characterizing self-assembled monolayers (SAMs) using X-ray photoelectron spectroscopy (XPS): 1- Perform XPS analysis on the SAM sample. 2- Measure kinetic energy and intensity of emitted photoelectrons. 3- Analyze energy levels and peak positions to identify elements and chemical states. 4- Quantify elemental composition and atomic concentration using peak intensities. 5- Assess chemical bonding, oxidation states, and surface chemistry based on binding energy shifts. 6- Utilize depth profiling techniques like angle-resolved XPS or depth-dependent sputtering. 7- Combine XPS with other techniques for comprehensive characterization of SAMs.

XPS provides essential information about elemental composition, oxidation states, and depth distribution within SAMs. It enables precise quantification of SAM coverage and thickness, crucial for optimizing device performance. Moreover, XPS offers insights into SAM-substrate interactions, including bond formation and charge transfer processes. Its versatility and sensitivity make it indispensable for researchers.

X-ray Photoelectron Spectroscopy (XPS): XPS provides information about the elemental composition and chemical bonding states of atoms present at the surface of SAMs. It can determine the thickness of SAMs and identify any contaminants or impurities present on the surface.

If the SAMs are alkanethiol-gold substrate-based conducting films, then a scanning tunneling microscope (STM) will give the SAMs' morphology, orientation, and thickness, etc. Atomic force microscopy can give topographical information along with mechanical properties of non-conducting films/samples.

Scanning Probe Microscopy (SPM) is a set of tip-based techniques including Atomic Force Microscopy (AFM), photo-induced microscopy, and Scanning Tunneling Microscopy (STM) etc. The biased sharp tip scans the surface, providing high-resolution images of the SAM's topography and revealing crucial details like surface roughness, layer thickness, dielectric properties, and packing density of the molecules.

Atomic Force Microscopy (AFM): ? Principle: Utilizes a sharp tip to scan the surface, mapping height variations. ? Application: Provides high-resolution images of SAM surfaces, offering information on roughness, morphology, and defects. Scanning Tunneling Microscopy (STM): ? Principle: Maps the surface using quantum tunneling current between a sharp tip and the sample. ? Application: Offers atomic-scale resolution, allowing visualization of SAM structures and defects.

Characterizing self-assembled monolayers (SAMs) using scanning probe microscopy (SPM): 1- Use AFM or STM for SAM characterization. 2- Obtain high-resolution topographic images with AFM, revealing SAM morphology and surface roughness. 3- Probe electronic properties and surface conductivity with STM by measuring tunneling current. 4- Combine AFM with functionalized tips or KPFM to map surface potential and work function variations. 5- Investigate mechanical properties and friction behavior with AFM-based nanomechanical measurements. 6- Utilize dynamic AFM modes like tapping or non-contact to minimize sample damage. 7- Integrate AFM/STM with spectroscopy or XPS for comprehensive understanding of SAM composition, structure, and properties.

Yes, for example we used SPM to see the AIDS and Covid virus in blood circulation around CD4 and CD8 Immunity providing White blood cells with inhibition technique ising our nanotech particles from colostrum

Cyclic voltammetry performed with gold electrodes previously modified with an alkylthiol-based SAM, enable for the measurement of the charging current (i), which serves for the calculation of the capacitance (C), according the equation C = i / v, where "v" represents the scan rate. Hence, if "i" is measured in mA and "v" in mV/s, the units for C will be mA/(mV/s) = As/V = C/V = F (farad).

Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) are highly effective techniques for analyzing the surface of SAMs. They provide detailed insights not only into morphology but also into chemical composition, bonding status, and more. By employing an electron source and interacting the electron beam with the sample, various types of information such as Energy-Dispersive X-ray Spectroscopy (EDS), Electron Energy Loss Spectroscopy (EELS), Secondary Electron Imaging (SE), and phase information can be extracted, offering a comprehensive understanding of the material.

Ellipsometry is an optical method that can be used to analyze self-assembled monolayers (SAMs). It measures changes in polarized light reflected from a sample. It's useful for precisely determining the thickness and refractive index of SAMs and understanding their electronic and optical properties. However, it works best with transparent or semi-transparent films and requires a well-defined model. Often combined with other techniques like XPS or AFM, ellipsometry provides a thorough characterization of SAMs.

SAMs quality can be confirmed with many different techniques, depending on the properties and applications of interest viz Raman spectroscopy for vibrational and rotational modes, HRXRD for the orientation mismatch, UV VIS spectroscopy for the their desired optical properties, Hall effect measurements to get electrical properties. ESR/EPR for the coherent time and spin states useful in quantum sensing applications.

I agree, but it depends on the objectives like in our case we used different technologies to study below 2000 daltons particles that can cross blood brain barrier to reach pituitary gland and modulate the immune system of the body as described in our several granted Patents in US and EU

Quartz Crystal Microbalance with Dissipation (QCM-D): ? Principle: Monitors changes in resonance frequency and dissipation of a quartz crystal. ? Application: Quantifies mass changes and viscoelastic properties of SAMs, providing real-time information on adsorption kinetics. Combining these analytical techniques allows for a comprehensive characterization of self-assembled monolayers, offering valuable insights into their structure, composition, and properties. The choice of techniques depends on the specific aspects of SAMs that need to be explored.

Depending on particle size and substate, SEM or TEM would be standard. Sample preparation can be tricky for both of them. SEM is quite handy because there are X-ray modules which give you atomic information in addition to the morphology.

One important thing to keep in mind is finding a quick, easy, and effective method for validating assembly is key. This is where techniques such as FTIR and UV-vis are most important. The data may not be as definitive as an NMR spectrum, however a quick scan showing the formation of a new peak due to a novel bond could be don’t in minutes. Although not a stand-alone piece of data, it can help guide research towards or away from specific techniques.

It should be very clear that the characterization of most of SAMs is not strait forward and numerous methods need to be used in combination in order to understand the structure and the properties. Unfortunately, there is still no "panacea" method that will give the whole picture. The study should be taken methodically and carefully with a lot of attention to small details the sometimes can change the conclusions polarly.

Characterizing self-assembled monolayers (SAMs) is crucial for various applications. Techniques like XPS, FTIR, contact angle measurements, AFM, ellipsometry, and QCM provide insights into SAM structure and properties. XPS identifies elemental composition and chemical state, FTIR analyzes molecular bonds, contact angle measures surface wettability, AFM images surface morphology, ellipsometry determines thickness, and QCM monitors mass changes. These techniques help optimize SAM performance in fields like surface modification and biosensors.