These giant gypsum cave crystals in Mexico grew very slowly in warm, stable, mineral rich water. (National Geographic)

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2 Nanoscience studies nature at the molecular level. Some molecules, given the right conditions, self-assemble in a regular pattern, for example, a crystal. These giant gypsum cave crystals in Mexico grew very slowly in warm, stable, mineral rich water. (National Geographic)

3 Module Objectives: Construct a model of crystal growth noting the structure that results when certain rules or conditions are applied Generate an understanding of self-assembly during the process of growing crystals. Apply the process skills of scientific inquiry during experimentation.

4 The Big Ideas of Nanoscale Science BIG IDEAS of Nanotechnology* Addressed: BIG IDEA #2 Structure of Matter The atomic theory describes a model on which matter is composed of discrete units called atoms. Slightly more than 100 types of atoms make up all substances. The type of atoms and their arrangements determine their identity and affect the properties of a material. BIG IDEA #6 Self-Assembly Under specific conditions, some materials can spontaneously assemble into organized structures. This process provides a useful means for manipulating matter at the nanoscale. BIG IDEA #8 Models and Simulations Scientists use models and simulations to help visualize, explain, predict, and hypothesize about structures, properties and behaviors of phenomena (e.g., objects, materials, processes, systems). The extremely small size and complexity of nanoscale targets make models and simulations useful for the study and design of nanoscale phenomena. Deb Newberry 2008

5 National Science Education Standards Addressed Science Physical Science Standards: Level 5-8: Properties and changes of properties in matter: Physical Science Standards: Level 9-12: Structure of atoms Structure and properties of matter NSES: All students should understand that scientists formulate and test their explanations of nature using observations, experiments and theoretical and mathematical models. Benchmarks for Science Literacy: Models are listed as a common theme of science.

6 Self-Assembly Crystals Module Science Inquiry Continuum Level: Guided Inquiry. Note: To increase the level of inquiry, encourage students to find the laboratory procedures to grow crystals as a research assignment. Basic Science Process Skills Applied: Observation, Prediction, Measurement, Recording and Analyzing Data (Communicating), Experimental Design Integrated Science Process Skills Applied: Experimenting, Acquiring Data, Analyzing Data, Analyzing Investigations, Understanding Cause and Effect Relationships, Formulating Models

7 Prerequisites/Traditional Concepts 14 Unit Cells Miller Indices Crystal Orientation Nomenclature Bravais Surfaces Chemical Bonding Atomic Level Structure

8 Growing Crystals: A Lesson on the Structure of Matter and Self-Assembly Grade Level: High School/Community College Content Integration: Chemistry, Mineralogy, Meteorology Background: Crystal arranged atoms in a particular order that repeats Scale nano, atoms are less than 1 nm in diameter Wow Factor beauty, strength, looks machined Modeling - molecular alignment causes a distinct lattice structure May be precipitated from a solution Heating allows more space and freer movement of atoms Super saturation decreases the space between atoms Seed crystals or nuclei determine the repeated pattern

9 Module Overview Molecules that exist in a disordered state such as a water based solution may spontaneously self-assemble into an ordered state. This process is driven by thermodynamics seeking an energy stable equilibrium. The result may be structures such a self-assembled monolayer, a lipid, or a crystal. This module will use a super-saturated solutions to observe some crystals that grow at a normal rate as well as those that grow in a matter of seconds. This module will demonstrate the key concepts that define selfassembly: 1. Order the molecules arrange themselves into a higher order 2. Reversibility the materials can be reused over and over

10 Pre activity Ask students to think of what defines a crystal Ask them to give examples of crystals Determine why gemstones are so valuable given their very common ingredients Study the strong and weak forces that bind atoms Study Gibbs Free Energy and the laws of thermodynamics

11 Self-Assembly Crystals Module Outcomes Students will be able to; List ten types of self-assembled structures various crystals, lipids, etc. Create a super-saturated solution. Explain various sources of activation energy needed to initiate crystal growth. Demonstrate the key concepts of self-assembly achieving higher order and reversibility. Measure the significant heat generated by rapid selfassembly and explain why the reaction was exothermic.

12 What are some examples of self-assembled structures? Crystals diamond, salt, sugar, giant gypsum, sapphire, ruby, Lipid-bilayers such as those found in cell walls Phase separated polymers (also known as block copolymers ) Self-assembled monolayers such as Graphene Self-folding proteins Silicon wafers used in integrated circuit fabrication Carbon nano tubes (CNTs)

13 Self-Assembled Crystals Module Activities and Evaluation Materials includes slow growth crystals, physical participation modeling, and more

14 Self-Assembled Crystals Module Activities and Evaluation Materials includes slow growth crystals, physical participation modeling, and more

15 Activities and Evaluation Materials Self-Assembled Crystals Module

16 Activities and Evaluation Materials Self-Assembled Crystals Module

17 Activities and Evaluation Materials Self-Assembled Crystals Module

18 Activities and Evaluation Materials Self-Assembled Crystals Module

19 Activities and Evaluation Materials complete module Self-Assembled Crystals Module

20 Activity Self-Assembled Crystals Using Super-Saturated Sodium Acetate Preparations Materials: Sodium Acetate Trihydrate purchased inexpensively online may be reused A source of heat energy such as a Bunsen burner, a hotplate, or a microwave oven Additional Materials Beakers or bowls for preparing the solution Plastic squirt bottle or transfer pipettes for washing small amounts of water down the sides of the beaker or bowl Scupula for transferring small numbers of Sodium Acetate crystals to the demonstration beaker or bowl Refrigerator for slowly cooling the super-saturated solution Add powdered Sodium Acetate Trihydrate to a beaker or small bowl Heat to break the powder s bonds and dissolve into a solution Squirt a little water down the sides of the beaker or bowl to wash off the powdered crystals which might trigger the self-assembly When the solution is very saturated but fairly clear transfer to a refrigerator for slow cooling Cool for an hour (less time for smaller amounts) Discuss what might supply enough activation energy to be the rapid self-assembly process Try various techniques for providing the activation energy: 1. Dropping a seed crystal into the super-saturated solution 2. Inducing a shockwave 3. Pouring the solution onto a seed crystal(s) to form a vertical structure

21 Now Ask students to guess what happens when a supersaturated solution is given sufficient activation energy.

22 While some crystals grow slowly, others can self-assemble with astonishing speed. This lab activity will demonstrate rapid crystal growth using a super-saturated solution of a common food additive, Sodium Acetate the flavor found in salt and vinegar potato chips It can be made from vinegar and baking soda.

23 In this activity you will transform sodium acetate from a white powder to a super-saturated liquid to a rapid growth crystal

24 Materials Sodium Acetate Trihydrate (some choose to make their own) A source of heat can be a Bunsen burner, hotplate, or microwave Glassware good for heating and viewing Water A squirter - for washing the sides of the beaker and adding a little water

25 Procedure Heat Sodium Acetate Trihydrate (SAT) powder (fairly gently) with a Bunsen burner, hotplate, or microwave (it melts at 58C). You may stir gently with a clean glass stir rod or swirl the beaker to mix. This takes about 20 minutes. Add water with a squirter by washing down the sides of the beaker or bowl say 30ml water for every 160 grams of SAT powder. This washes the powder granules off and reduces the chances of triggering the selfassembly reaction. When the solution is dissolved (may still be cloudy) carefully place it in a refrigerator to cool slowly for 30 minutes to an hour. When cooled it will become clear. You may have some settling on the bottom this is ok. The clear liquid will decant easily.

26 Procedure - continued The super-saturated solution is now ready for a trigger event adding sufficient activation energy to start the self-assembly reaction. Experiment with various triggers: dropping seed crystals into the solution, inducing a shockwave, or pouring onto seed crystals. Record the temperature of the exothermic reaction with a probe, a regular thermometer, or an infrared thermometer. Examine your crystals with an optical microscope. To image with a scanning electron microscope, first dehydrate the crystals on a specimen stub and then sputter coat. Demonstrate reversibility by reheating the crystals until they dissolve, adding a little water to replace some that was lost to evaporation.

27 Triggering the self-assembly with a seed crystal

28 Video Hans Mikelson of Chippewa Valley Technical College Some more fine videos online:

29 Video Out-takes With CVTC s Hans Mikelson watch?v=plpb1o5r88e atch?v=snvcslr8mvo atch?v=n0btx3mfxgo

30 Some Questions Why was the crystal growth exothermic? What are some practical uses for a super-saturated solution of Sodium Acetate Trihydrate? (Think winter sports such as hunting when one s hands or toes get cold) What is super saturation? How can this example of self-assembly be reversed? Why is your Sodium Acetate Trihydrate crystal not as valuable as a diamond made of carbon? How could one image the crystal structure? What type of crystal lattice does Sodium Acetate Trihydrate represent?

31 Self-Assembly Crystals Module Related Activities Try forming slow growth crystals of Epsom salt, borax, alum, or sugar Get students out of their seats to model self-assembly (see Nanolink Resources) Draw accurate crystal lattice structure types with CAD Collect crystals and study the conditions they need to grow Make nanoscale block copolymer structures with a vacuum oven and study how they might be used in applications such as photovoltaics Learn how artificial diamonds are made Watch Silicon Run to see how silicon ingots are grown from a seed crystal. Learn which elements contribute to a gemstone s brilliant color Experiment with the solutions found in commercial hand-warmers Image a dehydrated Sodium Acetate Trihydrate crystal in an SEM

32 One Related Activity - Modeling CAD drawing of four common crystal structures

33 Another Related Activity - Imaging Sodium Acetate Trihydrate crystal showing typical monoclinic structure image by K. Carlson, Chippewa Valley Technical, 2011

34 Thank You Deb Newberry Jeannine Stanaway Kristi Jean Karen Halverson Rick Barrett Hans Mikelson John Wagner Stacy Carrell-Atchison Michael Patterson Anna Garden Matt Pleil