🫳Intro to Nanotechnology Unit 5 – Nanomaterial Characterization Techniques

Key Concepts and Definitions

• Nanomaterials have at least one dimension between 1-100 nanometers (nm)
• Nanostructures can be classified as 0D (quantum dots), 1D (nanotubes, nanowires), 2D (graphene, thin films), or 3D (nanoparticles, nanoporous materials)
• Characterization involves determining the physical, chemical, and structural properties of nanomaterials
• Surface area to volume ratio significantly increases at the nanoscale, leading to unique properties and behaviors
• Quantum confinement effects occur when the size of a material approaches the nanoscale, affecting its electronic and optical properties
• Nanomaterial synthesis methods include top-down (lithography, etching) and bottom-up (chemical vapor deposition, sol-gel) approaches
• Nanoscale interactions are governed by forces such as van der Waals, electrostatic, and capillary forces

Importance of Nanomaterial Characterization

• Ensures the quality, purity, and consistency of nanomaterials for reliable performance in various applications
• Helps understand the structure-property relationships of nanomaterials, enabling the design of materials with desired properties
• Allows for the optimization of nanomaterial synthesis processes by providing feedback on the resulting material properties
• Enables the identification of potential hazards or toxicity associated with nanomaterials, ensuring safe use and handling
• Facilitates the development of new applications by revealing unique properties and behaviors of nanomaterials
• Supports the reproducibility and comparability of research results across different laboratories and institutions
• Plays a crucial role in the commercialization and quality control of nanomaterial-based products

Common Nanomaterial Types

• Carbon-based nanomaterials
  • Carbon nanotubes (single-walled and multi-walled)
  • Graphene and graphene oxide
  • Fullerenes (C60, C70)
• Metal nanoparticles (gold, silver, copper)
• Metal oxide nanoparticles (titanium dioxide, zinc oxide, iron oxide)
• Semiconductor nanoparticles (quantum dots)
  • Cadmium selenide (CdSe)
  • Indium phosphide (InP)
• Polymeric nanoparticles (dendrimers, micelles)
• Silica-based nanomaterials (mesoporous silica, silica nanoparticles)
• Composite nanomaterials (core-shell structures, nanocomposites)

Physical Characterization Techniques

• Electron microscopy
  • Scanning electron microscopy (SEM) for surface morphology and topography
  • Transmission electron microscopy (TEM) for internal structure and crystallinity
• Atomic force microscopy (AFM) measures surface topography and mechanical properties at the nanoscale
• X-ray diffraction (XRD) determines the crystal structure, phase composition, and crystallite size of nanomaterials
• Dynamic light scattering (DLS) measures the hydrodynamic size distribution of nanoparticles in suspension
• Brunauer-Emmett-Teller (BET) analysis quantifies the specific surface area of nanomaterials based on gas adsorption
• Thermogravimetric analysis (TGA) assesses the thermal stability and composition of nanomaterials
• Differential scanning calorimetry (DSC) investigates the thermal transitions and phase changes in nanomaterials

Chemical Characterization Methods

• Energy-dispersive X-ray spectroscopy (EDS or EDX) provides elemental composition information when coupled with electron microscopy
• X-ray photoelectron spectroscopy (XPS) analyzes the surface chemistry and oxidation states of nanomaterials
• Fourier-transform infrared spectroscopy (FTIR) identifies functional groups and chemical bonds in nanomaterials
• Raman spectroscopy probes the vibrational modes and structural properties of nanomaterials, particularly useful for carbon-based nanomaterials
• Zeta potential measurements assess the surface charge and colloidal stability of nanoparticles in suspension
• Inductively coupled plasma mass spectrometry (ICP-MS) quantifies trace elements and impurities in nanomaterials with high sensitivity
• Nuclear magnetic resonance (NMR) spectroscopy elucidates the chemical structure and local environment of atoms in nanomaterials

Imaging and Microscopy Techniques

• Scanning tunneling microscopy (STM) provides atomic-scale imaging of conductive surfaces
• High-resolution transmission electron microscopy (HRTEM) reveals the atomic structure and lattice fringes of crystalline nanomaterials
• Scanning transmission electron microscopy (STEM) combines the principles of SEM and TEM for high-resolution imaging and chemical analysis
• Atomic force microscopy (AFM) modes
  • Contact mode for surface topography
  • Tapping mode for soft or delicate samples
  • Phase imaging for mapping surface properties
• Kelvin probe force microscopy (KPFM) maps the surface potential and work function of nanomaterials
• Environmental scanning electron microscopy (ESEM) allows imaging of non-conductive and hydrated samples without the need for sample preparation
• Confocal laser scanning microscopy (CLSM) enables three-dimensional imaging of fluorescently labeled nanomaterials in biological systems

Data Analysis and Interpretation

• Statistical analysis of size distribution, shape, and morphology data obtained from microscopy techniques
• Spectral deconvolution and peak fitting for XPS, FTIR, and Raman data to identify chemical species and quantify their relative abundances
• Rietveld refinement of XRD patterns to determine the crystal structure, lattice parameters, and phase composition of nanomaterials
• Scherrer equation for estimating the average crystallite size from XRD peak broadening
• Porod analysis of small-angle X-ray scattering (SAXS) data to characterize the surface roughness and fractal dimension of nanomaterials
• Quantitative analysis of elemental composition using EDS or ICP-MS data
• Correlation of physical, chemical, and structural properties to understand the structure-property relationships in nanomaterials

Applications and Case Studies

• Nanomedicine
  • Targeted drug delivery using functionalized nanoparticles (liposomes, polymeric nanoparticles)
  • Magnetic nanoparticles for hyperthermia cancer therapy and MRI contrast enhancement
• Energy storage and conversion
  • Nanostructured electrodes for high-performance lithium-ion batteries (silicon nanowires, graphene-based materials)
  • Quantum dot solar cells for enhanced light harvesting and energy conversion efficiency
• Environmental remediation
  • Photocatalytic degradation of pollutants using titanium dioxide nanoparticles
  • Adsorption of heavy metals and contaminants by nanoporous materials (zeolites, metal-organic frameworks)
• Sensors and diagnostics
  • Gold nanoparticle-based colorimetric sensors for the detection of biomolecules and pathogens
  • Carbon nanotube-based gas sensors for environmental monitoring and industrial safety
• Nanoelectronics and optoelectronics
  • Quantum dot light-emitting diodes (QD-LEDs) for display applications
  • Graphene-based transistors for high-speed and low-power electronic devices