In Situ Microscopy and Spectroscopy Applied to Surfaces at Work

The present review discusses the current state of the art microscopic and spectroscopic characterization techniques available to study surfaces and interfaces under working conditions. Microscopic techniques such as environmental transmission electron microscopy and in situ transmission electron microscopy are first discussed showing their applications in the field of nanomaterials and catalysis. Next sum frequency generation vibrational spectroscopy is discussed, giving probing examples of surface studies in gaseous conditions. Synchrotron based X-ray techniques are also examined with a specific focus on ambient pressure X-ray photoelectron and absorption techniques such as near and extended X-ray absorption fine structure. Each of the techniques is evaluated, whilst the pros and cons are discussed in term of surface sensitivity, spatial resolution and/or time resolution. The second part of the articles is articulated around the future of in situ characterization, giving examples of the probable development of the discussed techniques as well as an introduction of emerging tools such as scanning transmission X-ray microscopy, ptychography, and X-ray photon correlation spectroscopy

SUM FREQUENCY GENERATION IMAGING MICROSCOPY (SFGIM): CHEMICAL IMAGING OF PATTERNED SAMs ON GOLD BASED ON THE COMPOSITION, ORIENTATION AND DISTRIBUTION

Author Institution: Department of Chemistry, University of Houston, Houston, Texas, 77004;This project focuses on the construction and development of the SFG imaging microscope with its application on thiol molecules on gold metal surfaces. The application investigates the orientation of the thiol monolayer on Au with different terminal functional groups, chain lengths and the number of sulfur atoms bound to the metal. The chemical contrast on the images is based on the vibrational spectrum of the molecules oriented at the interface. The microcontact printing process used PDMS stamps with 100 micron x 100 micron checkered features with phenyl-terminated C16 thiol and methyl-terminated C17 thiol/dithiol molecules. The microscope was able to determine a chemical contrast distinction on the surface based on different functionality of the terminal group(methyl vs. phenyl-terminated C16 thiols). On the other hand, the C16 vs. C17 thiols/dithiols demonstrated chemical contrast based on the orientation at the interface (tilt angle). The SFG results showed that more mixing based on the chemical contrast and orientation was observed closer to the border between to different molecule and the dithiols formed a well-ordered monolayer compared to normal alkanethiols. SFG imaging is able to distinguish the location of molecules on the surface based on their inherent vibrational spectrum

Breast day ever: An event plan on reducing breast cancer misconceptions

The Philippine Foundation for Breast Care Inc. (PFBCI) is an organization that aims to help individuals currently diagnosed with breast cancer as well as educate Filipino women about breast cancer and the importance of breast care. PFBCI\u27s main communication effort is a seminar in delivering their advocacy. However, the researchers found out that despite the aim of the organization to provide credible breast cancer information and correct misconceptions on breast cancer of female college students, specifically, the information that PFBCI is sending out are not aligned to their initial goal. It was revealed that it is because the information given in their seminar were shaped to address women who are already diagnosed with the disease, rather than for individuals who are prone to acquiring breast cancer and have not yet been diagnosed. The misconceptions raised in a focus group discussion were the following: 1) breast cancer only occurs to women ages 35 and above, 2) early detection leads to total remission from breast cancer 3) self-breast exams should only be performed every 6 months, 4) that mammograms can eliminate the risk of breast cancer occurrence, 5) breast cancer is heredity, 6) breast cancer can only be detected in the form of lumps, 7) breast cancer only occurs in lower social classes and, 8) that doing one or more of the breast cancer prevention methods is enough to spare them from breast cancer. Hence, the researchers, in collaboration with PFBCI, created an event last June 24, 2015 at the SM Megamall. The event aimed to reveal, correct, and address breast cancer misconceptions not just of female college students, but the rest of the attendees who were older women and men

In-situ ellipsometry measurements on the phase segregation of mixed halide lead perovskites

Mixed halide lead perovskite such as methylammonium lead iodide bromides MAPb(BrxI1-x)3 have emerged as one of the most promising materials of future solar cells, offering high power conversion efficiencies and bandgap tunability. Among other factors, the reversible phase segregation under even low light intensities is still limiting their potential use. During this process, the material segregates locally into iodide-rich and bromide-rich phases, lowering the effective bandgap energy. While several studies have been done to illuminate the mechanism and suppression of phase segregation, fundamental aspects remain unclear. Phase compositions after segregation vary extensively between different studies and the exact amounts of phases often remain unmentioned. For iodide-rich phases, the end-point compositions at around x=0.2 are widely accepted but the proportion of the phase is difficult to measure. In this report, we observe the phase segregation using spectroscopic ellipsometry, a powerful, nondestructive technique that has been employed in the study of film degradation before. We obtained dynamic ellipsometric measurements from x=0.5 mixed halide lead perovskite thin films protected by a polystyrene layer under green laser light with a power density of ~11 W/cm2. Changes in the bandgap region can be correlated to the changes in composition caused by phase segregation, allowing for the kinetics to be observed. Time constants between 1.7(± 0.7)×10-3 s-1 for the segregation and 1.5(± 0.6)×10-4 s-1 for recovery were calculated. We expect ellipsometry to serve as a complementary technique to other spectroscopies in studying mixed-halide lead perovskites phase segregation in the future

Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy

© The Author(s) 2019. Sum frequency generation (SFG) Equal contributors. spectroscopy was used to deduce the orientation of the terminal methyl (CH3) group of self-assembled monolayers (SAMs) at the air–solid and air–liquid interfaces at surface concentrations as low as 1% protonated molecules in the presence of 99% deuterated molecules. The SFG spectra of octadecanethiol (ODT) and deuterated octadecanethiol (d37 ODT) SAMs on gold were used for analysis at the air–solid interface. However, the eicosanoic acid (EA) and deuterated EA (d39 EA) SAMs on the water were analyzed at the air–liquid interface. The tilt angle of the terminal CH3 group was estimated to be ∼39 ° for a SAM of 1% ODT : 99% d37 ODT, whereas the tilt angle of the terminal CH3 group of the 1% EA : 99% d39 EA monolayer was estimated to be ∼32 °. The reliability of the orientational analysis at low concentrations was validated by testing the sensitivity of the SFG spectroscopy. A signal-to-noise (S/N) ratio of ∼60 and ∼45 was obtained for the CH3 symmetric stretch (SS) of 1% ODT : 99% d37 ODT and 1% EA : 99% d39 EA, respectively. The estimated increase in S/N ratio values, as a measure of the sensitivity of the SFG spectroscopy, verified the capacity to acquire the SFG spectra at low concentrations of interfacial molecules under ambient conditions. Overall, the orientational analysis of CH3 SS vibrational mode was feasible at low concentrations of protonated molecules due to increased S/N ratio. In support, the improved S/N ratio on varying incident power density of the visible beam was also experimentally demonstrated