Advanced Laboratory in Physical Chemistry

This lab is designed for teaching advanced experimental techniques in physical chemistry during the last semester of B.Sc. studies, and it is mostly performed in various laboratories at the school of chemistry using equipment that is used for contemporary research.

The experiments are performed by pairs of students, where each pair performs 3 experiments out of the list appearing below during the semester.

The faculty members responsible for the lab are:

Prof. Ori Cheshnovsky

Prof. Gil Markovich

1. Scanning Probe Microscopy (AFM)
   
   Abstract: This lab teaches the operation principles of the Atomic Force Microscope (AFM). The experiment is performed in the lab of Prof. Gil Markovich.

   The AFM scans the surface of a samples, and based on the forces acting between the surface and the scanning tip, it is possible to obtain a topographic map of the surface with atomic scale resolution.

   In this lab, the AFM will be used to analyze samples produced in a research project on semiconductor nanowires.

   
   
    
2. Langmuir-Blodgett Films (LB)
   
   Abstract: In this experiment the Langmuir-Blodgett (LB) technique is used to prepare mono-molecular films. Those films are made of amphiphilic molecules (having a hydrophilic head and hydrophobic part. These films are prepared at the air-water interface. When spread at low enough concentration, these molecules, due to the different nature of their two parts, will be trapped at the interface, having the hydrophilic part dissolved in the water and hydrophobic residue in the air. Two-dimensional compression experiments will be performed on these trapped molecules in the LB instrument and by measuring the compression isotherms, phase transitions of the films will be observed and analyzed.
   
   
    
3. Point Contact and Molecular Junctions
   
   Abstract: This experiment deals with fabrication methods, characterization and electrical measurements of molecular junctions. The experiment is divided in three parts. The first part teaches the photolithography technique, which is the main method used for fabrication of microelectronic devices. This part is performed in the clean-room at the center for nanoscience and nanotechnology. In the second part, the electromigration method for creating point-contact and molecular junctions will be introduced. This part is performed at the lab of Prof. Yoram Selzer and includes electrical characterization of the junctions. The third part teaches about scanning electron microscopy (SEM) and will be used to characterize the samples produced in the previous parts.
   
   
    
4. Raman Spectroscopy
   
   Abstract: This experiment teaches an optical measurement technique based on interaction of light with vibrational energy levels in materials in a process named Raman scattering. In this experiment, performed in the lab of Prof. Ori Cheshnovsky, the students learn the theoretical principles of the technique and the details of the experimental system, consisting of a microscope, laser light source, spectrograph and sensitive light detectors. The system is used to characterize various materials, including single grapheme layers and carbon nanotubes. In addition, the students monitor the temperature in electronic devices by measuring the population of different vibrational energy levels. This lab provides knowledge about research tools that are important for optics industry and research.
   
   
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5. Nuclear magnetic resonance (NMR)
   
   Abstract: This experiment is designed to teach the physical aspects of NMR research. The lab complements the courses on basics of NMR and NMR applications in chemistry and medicine. Unlike the use of NMR for organic chemistry teaching, where analysis of the chemical shift spectra is the focus, here the emphasis is on measurement methods. The first meeting is used to study the NMR basics and at the end of this meeting a simple one-dimensional NMR spectrum is obtained. In the second week relaxation measurements are taught and performed and the third week is used to teach advanced topics that may change from time to time, such as: dynamic NMR, magnetization transfer, two-dimensional NMR, diffusion measurements.
   
   
    
6. Time Correlated Single Photon Counting (TCSPC)
   
   Abstract: This experiment probes the significant chemical changes occurring upon excitation of a solvated molecule to an excited electronic state. The observed change is a change in the pKa value of the molecule, i.e., a change in its acidity. Molecules experiencing such a change are called photo-acids. The experiment teaches the basics of optical spectroscopy, with emphasis on the absorption and fluorescence spectroscopies. Fluorescence decay times will be measured using the TCSPC technique. In this experiment we will correlate the results from TCSPC measurements and fluorescence spectra to the change in the pKa value of the molecule 8-Hydroxypyrene-1,3,6-trisulfonic acid, which is a common photo-acid.
   
   
    
7. Colloidal suspension – a tool to observe the microscopic properties of material phases
    

   Abstract: In this lab, we will investigate the motion and the spatial arrangement of molecules in a gas and in a liquid by studying a model system, a colloidal suspension, in which the colloidal particles act as model molecules. We will observe colloidal suspension of various densities using optical microscopy, using image analysis tools (single particle tracking) to follow their motion. We will focus on two different observables to compare the behavior of, molecules in a gas and in a fluid:

   1. Dynamics of a single molecule: diffusion.

   2. Spatial arrangement of the colloidal suspension: the pair correlation function g(r).
      
      
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8. Single Molecule Epectroscopy
   
   Abstract: The experiments carried out in the lab of Prof. Yuval Ebenstein will teach basics of fluorescence microscopy and its application for the analysis of epigenetic modifications on single DNA molecules. We will assemble a fluorescence microscope, then use it to image DNA molecules that are stretched out on surfaces and labelled with an intercalating fluorescent dye. In the second part, we will label epigenetic modifications on genomic DNA with aside groups, use click chemistry to attach two different fluorescent dyes and compare the bleaching behavior of single dye molecules. For this we will work with a more-advanced fluorescence microscope in the Ebenstein lab.
   
   
    

9. Random Walk - Group A, Random Walk - Group B
   
   Abstract: The term "random walk" was first coined in 1905 by Karl Pearson as part of a question he presented to the readers of the journal Nature:

   "Can any of your readers refer me to a work wherein I should find a solution of the following problem, or failing the knowledge of any existing solution provide me with an original one? I should be extremely grateful for aid in the matter. A man starts from a point "O" and walks "l" yards in a straight line; he then turns through any angle whatever and walks another "l" yards in a second straight line. He repeats this process "n" times. I require the probability that after "n" stretches he is at a distance between "r" and "r+δr" from his starting point "O".

   More than a century later, the theory of random walks has greatly evolved and it is now routinely applied in physics (diffusion, polymers), chemistry (chemical reactions), biology (from the motion of organisms to that of organelles and molecules inside the cell), and economics (models of stock exchange). In this theoretical/computational lab you will familiarize yourself with random walks and their applications through a hands-on problem-solving approach.