In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

The overall goal of the following experiment is to prepare extremely pure and precisely defined organo metallic molecules on surfaces so that structure reactivity relationships, and ion surface interactions may be characterized using a combination of NC two sims and IR spectroscopy techniques. This is achieved by first preparing a solution of the organo metallic compound in methanol and loading it into a syringe pump for injection into an electro spray ionization source. As a second step collision induced association is performed in the high pressure source region of the soft landing instrument, which removes one by purine ligand from each doubly charged ruthenium tris by purine ion forming highly reactive, under coordinated, doubly charged ruthenium bis by purine ions.

Next mass selection is achieved using a quadruple mass filter followed by soft landing in order to prepare surface bound organo metallic ions without any contamination from unwanted species, solvent molecules or counter ions, Sims and Eris are used for NNC two characterization of the surfaces. Results demonstrate organ metallic ions immobilized on self-assembled monolayer surfaces by soft landing of mass selected ions. The main advantage of this method over existing techniques such as spin coating and drop casting, is that mass selection enables atomically precise control over the size charge, state, and composition of materials delivered to surfaces.

This method can help answer key questions in the energy storage field, such as whether the size and ionic charge. State of redox active metal oxide clusters can control the structure and stability on surfaces. Though ions soft landing provides insights into the sensitivity of catalytic and energy storage materials to size and composition.

It has also been applied to other systems such as peptides, proteins, and viruses that have broad applications and biological sensing and diagnostics. First place a previously prepared self-assembled monolayer or SAM surface onto one of three metal sample mounts. Open the sample introduction door and secure the sample holder firmly to the manipulator inside of the instrument.

Following this, close the door and open the valve to the four line mechanical vacuum pump. When the sample introduction chamber reaches the pressure of 10 to the minus third tor turn on the turbomolecular vacuum pump and ization pressure gauge. When the sample introduction chamber reaches a pressure of 10 to the minus six tour, open the gate valve to the soft landing chamber.

Use the magnetic manipulator or XY, Z stage to position the SAM surface in line with the ion beam to begin soft landing. For each instrument load 0.5 milliliters of previously prepared 0.01 millimolar tris two two prime by pur di chloro. Ruthenium two hexahydrate solutions into a one milliliter glass syringe.

Mount the syringe into a syringe pump and apply plus two to plus three kilovolts to the capillary to generate positive ions. Then adjust the syringe pump flow rate to between 20 to 40 microliters per hour to obtain an optimum ion current of the surface. Adjust the quadruple mass filter to the mass of the doubly charged ruthenium bis by purine ion.

Then adjust the voltage settings of the ion optics and radio frequency ion guides to maximize the ion current and stability of the doubly charged ruthenium tris by purine ion measured at the SAM surface. Following this, increase the potential gradient in the high pressure collision quadripole region of the soft landing instrument to enable gas phase ligand stripping from the organal metallic ion through collision induced dissociation. Upon completion of the deposition, turn off the syringe pump and the high voltage to the ESI emitter.

Use the magnetic manipulator to move the prepared surface from the soft landing chamber to the analysis stage inside the to sims part of the instrument. Next, disengage the manipulator from the sample and retract it fully from the SIMS analysis chamber. Close the gate valve between the soft landing and sims part of the instrument.

To conduct the TOF sims experiment. Load the instrument control file in the software and ensure that the gallium ion source is producing a sufficiently stable current of primary ions. Acquire x and Y-axis line profiles across the surface to determine the center of the deposited spot of ions on the substrate.

Position the surface so that the gallium primary ion beam is incident on the center of the deposited spot of ions. Then acquire a toff sims mass spectrum for five minutes. Following this, turn off the primary gallium ion beam and the high voltages of the toff sims instrument.

Use the magnetic manipulator to move the sample back into the soft landing part of the instrument. Use a high vacuum leak valve to introduce a controlled flow of ultra high purity oxygen gas from a cylinder into the instrument. Use the adjustable gait valve to throttle the pumping speed of the pump to achieve a steady state pressure of 10 to the minus four tor of oxygen inside the soft landing chamber.

Repeat the previous steps to characterize the soft landed ions following exposure of the surface sequentially to oxygen and ethylene for 30 minutes. Position a circular SAM surface at the rear trapping plate of the ICR cell located inside of the six Tesla magnet. Then uses cesium ion source to create a continuous beam of eight kilovolt cesium primary ions during this trap and analyze the secondary ions ejected from the surface using FT IC RM MS for infrared reflection absorption spectroscopy direct the infrared light from the spectrometer onto the carboxylic acid terminated monolayer surface positioned inside the vacuum chamber.

Utilize a gold coated flat mirror to direct the light exiting the FTIR spectrometer onto a parabolic gold mirror. Next, reflect the light from the parabolic mirror through a mid-infrared zinc selenide wire grid polarizer and into the vacuum chamber. Through a viewport position the reflective SAM on the gold surface inside the vacuum chamber at the focal point of the first parabolic mirror using the motor driven Z translator.

Then reflect the IR light, exiting the vacuum chamber from the surface of the SAM through a second viewport. Use a second parabolic gold mirror to focus the reflected light from the surface onto an MCT detector. Finally, acquire spectra at set intervals during the deposition process.

A peak corresponding to a ruthenium bis paridine thiol covalent adduct at a master charge ratio of 700 is observed here, which indicates very strong binding between the under coordinated ion and the monolayer surface. The peaks corresponding to this species are featured prominently Here presented Here are the NC two to F sim spectra obtained directly following exposure of the carboxylic acid terminated SAM surfaces containing soft landed doubly charged ruthenium tris by purine ions and doubly charged ruthenium bis by purine ions to gaseous oxygen. The peaks are consistent with the addition of atomic and molecular oxygen to the organ metallic surface adduct respectively.

Moreover, this adduct appears to be oxidized with close to 50%conversion efficiency. The to F SIM spectrum following exposure to ethylene indicates a decrease in the relative abundance of the singly oxidized organ metallic adduct at a mass to charge ratio of 716. A scheme describing what is achieved for this representative system through the combination of ion soft landing and analysis by NC two to sims is presented here.

Representative results for doubly charged ruthenium tris by purine ions landed onto the carboxylic acid terminated SAM surface are presented here during soft landing. The doubly charged ruthenium tris by ion exhibits a linear increase in abundance on the carboxylic acid terminated SAM surface. The measured abundance reaches a maximum at the end of soft landing and is followed by an extended plateau on the carboxylic acid terminated SAM surface.

The singly charged ions in comparison are depleted more rapidly following the end of soft landing. The infrared spectrum obtained following soft landing of five times 10 to the 12th, doubly charged ruthenium tris by purine ions onto the carboxylic acid terminated SAM surface is presented here. Nine vibrational features are noted with an asterisk in the IR spectrum as unique spectroscopic signatures of doubly charged ruthenium tris by pyridine.

Once mastered, the soft landing experiment can be set up in less than an hour. Okay, following deposition, the sample can be characterized using A-F-M-T-E-M and STM to further examine the surface coverage and secondary structure of soft landed ions After its development. This technique paved the way for researchers in the field of catalysis to explore structure reactivity relationships in clusters and nanoparticles with unprecedented precision.