Master degree in Materials Science

Surface phenomena at the micro and nano scale

Surface phenomena at the micro and nano scale

Academic year 2023/2024

Sommario del corso

• Course objectives
• Results of learning outcomes
• Program
• Course delivery
• Learning assessment methods
• Support activities
• Notes
• Class schedule
• Teaching tools
• Course card

Course objectives

The surface is the link between a body and the environment. As such, the surface is the place where many physical and chemical phenomena take place, and in many cases determines the behaviour of the material in practical applications.

The main objective of the course is to gain an understanding of the main phenomena occurring at the surfaces of materials, merging physical and chemical concepts. It complements the knowledge acquired during the courses of Solid State Physics and Crystallography, answering the fundamental question: what happens to the properties of an infinite solid when the lattice periodicity ends at a surface?

Another objective of the course is to introduce the most important techniques that can be used to characterize surfaces and their respective capabilities and providing the knowledge to be able to choose the appropriate surface approach for solving real problems.

Results of learning outcomes

• Ability to foresee and understand the physics of solid-gas surface phenomena
• Ability to interpret the outcome of volumetric measurements for different types of materials
• Understand how to use microcalorimetry to investigate surface phenomena
• Understand the surface chemistry of different categories of materials and how it is related to technologically important fields like heterogeneous catalysis
• Know the basic principles of surface-sensitive spectroscopies
• Analyze examples from surface science techniques
• Investigation of the factors that cause biological surfaces to have superb functionalities.

Program

FRONTAL LESSONS

• BULK, SURFACES AND INTERFACES (prof. Groppo)

Definition of interface and surface / Different types of surfaces: external and internal / Thermodynamic at surfaces / Surface tension for liquids / Minimization of the surface tension for solids / Adsorption from the gas phase / Relaxation and reconstruction / Assuming a spherical shape / Nano-scale effects on the materials properties / Adsorption (physisorption and chemisorption) / Thermodynamics of surfaces, surface tension, nucleation; Wulff construction and equilibrium shapes.

• METHODS FOR MEASURING THE SURFACES (prof. Groppo and prof. Crocellà)

Rapid overview on the main surface science techniques (spectroscopies: XPS, LEED, EELS; microscopies: STM, AFM) / Surface science at the dawn of the 21st century: solid/gas interface at ambient pressures.

Adsorption processes (physisorption and chemisorption). Quantitative expression of adsorption (adsorption isotherms). Porous materials and classifications of pores (micropores, mesopores and macropores). Volumetric techniques. Surface area and pore structure determination by gas adsorption. Classification of gas physisorption isotherms. Choice of the adsorptive for textural properties evaluation: N2 adsorption at 77 K, Ar adsorption at 87 K, CO2 adsorption at 273 K. Equations used to describe experimental isotherms. Assessment of microporosity and mesoporosity: BJH, t-plot and NL-DFT methods. Experimental methods for the determination of the heat of adsorption (micro-calorimetry).

• WHEN THE SURFACE IS MAINLY INTERNAL (prof. Crocellà and prof. Bordiga)

Mesoporous materials, synthesis (by hard and soft templating), properties and examples of applications.

Microporous materials: Synthetic zeolites and aluminium phosphate.  Definition and description of a zeolite, zeolite topologies and morphologies. Strategies in synthesis of zeolites. AlPO and SAPO: a comparison with zeolites. How to measure the surface acidity (FT-IR of molecular probes). How to monitor the oxidation state of metal sites in zeolites. The synergy between active sites and porosity. Some examples of applications in catalysis (acid catalysis; redox catalysis).

• SURFACE PROPERTIES OF METAL-OXIDES (prof. Groppo)

General properties of metal oxides / Crystal structures / Electronic properties / Surface properties: surface reconstruction, hydroxyl groups, acidity/basicity and red-ox properties, surface defects.

Silica and silicates and the role of OH groups / Structures/ Synthesis method: pyrogenic silica, sol-gel processes / Surface chemistry: surface OH groups and IR spectroscopy for detecting the OH groups/ Reactivity at the silica surface: the SOMC approach.

Alumina and surface acidity / crystalline structures and polymorphs / Synthesis and crystal habits/ Surface chemistry: surface OH group, Lewis acid sites, basic sites/ Detection of acid sites by IR spectroscopy of basic probe molecules: the cases of pyridine and CO / Reactivity at the alumina surface.

MgO and ZnO: acid-base couple at the surface / Crystalline structures, morphology, and synthesis strategies / Surface chemistry and ability in H2 splitting

TiO2: synergy between surface and bulk / a few principle of photocatalysis / H2O photolysis / Photo-decomposition of pollutants / Photo-induced hydrophilicity and antifogging effect, self-cleaning and cooling functions /Defects in TiO2, black TiO2 and electronic levels in the band-gap

• THE SURFACE OF METALS AND METAL NANOPARTICLES (prof. Groppo)

Adsorption sites and defects at the surface of metals / Adsorbate geometries / CO as molecular probe / Surface reconstruction / Reactivity at metal surfaces: the case of H2 (surface, sub-surface and bulk hydrides) / Methods for characterising metal hydrides

Metal nanoparticles / Shapes of metal nanoparticles / Synthesis methods, the role of stabilizers and/or supports / Supported metal nanoparticles: metal-support interaction, sintering and re-dispersion, particle size and dispersion / Methods for particle size measurements.

• QUANTUM DOTS AND QUANTUM WELLS (prof. Yum)

Basic properties of QDs and QWs / Formation of QDs / Application of QDs, e.g. LEDs and Solar cells.

• SEMICONDUCTOR AND LIQUID INTERFACE (prof. Yum)

Semiconductor junction / Semiconductor and liquid junction / Methods to characterize the junctions / Redox reaction / Standard electrode potential / Light absorption by semiconductors / H₂ reduction on the surface of semiconductor / Photoelectrochemial water splitting / Methods and metrics to evaluate photoelectrochemical water splitting / Examples of photoelectrodes (inorganic materials and organic materials) / Issues in surface and bulk.

LABORATORY

• Application of N₂ and Ar physisorption for characterizing materials with different surface area and porosity (micro- and meso-pores)
• Application of microcalorimetry for estimating the heat of adsorption of probe molecules on different types of materials
• Use of FT-IR spectroscopy of adsorbed probe molecules for distinguishing different types of adsorption sites at the surface of materials.
• Use of DR UV-Vis spectroscopy for investigating surface defects in semiconducting materials (e.g. TiO₂).

Course delivery

Frontal lessons and laboratory activities will be held in presence 

Lessons: 6 CFU (48 hours)

Laboratory: 1 CFU (16 hours) - the lab part will be carried out by dividing the class into small groups to allow access to all research instruments

Practical exercise: 1 CFU (12 hours)

Total: 8 CFU (76 hours)

Attendance at the lessons is not compulsory. Attendance at the laboratory and practical exercise is compulsory and cannot be less than 70% of the total.

All the teaching material will be published on the Moodle page of the course.

Learning assessment methods

The exam will consist of a written test (to be done in presence in the informatic classroom) and an oral part (in presence).

WRITTEN TEST:

The written test is propaedeutic to the oral. It consists of 21 closed questions through the Moodle platform. Only those students who pass the written test with a mark of at least 21/30 will be admitted to the oral, which will take place right after the written test.

ORAL:

The oral will take place right after the written test, in presence. The oral part will be conducted starting from the comment on the laboratory activities. During this discussion, additional questions will be done, to verify the knowledge of the topics developed in the frontal lessons of the course.

The final mark is expressed in thirtieths and will depend both on the written test and on the oral. The written test will count for 10% of the final mark, whereas the oral part will count for 90% of the final grade.

The students who will pass the written test but will not pass the oral will also have to repeat the written test in future sessions.

Support activities

The teachers can be contacted through e-mail to discuss and clarify any concept explained during the lessons.

Elena Groppo: elena.groppo@unito.it

Silvia Bordiga: silvia.bordiga@unito.it

Valentina Crocellà: valentina.crocella@unito.it

Notes

Class schedule

• Teaching material
• Exams and finals
• Class schedule
• Go to Moodle
• Register for the course
• Enrolled students
• Invia email agli studenti registrati
• Export table