Characterisation techniques

How XRD, XPS, BET, electron microscopy, NMR, FTIR, Raman, thermal analysis, UV–vis, DLS, electrochemistry and ICP-MS work, what their data looks like and how to read it, with every fact cited to the literature. Each page has the instrument and an example data plot you can edit in LabCanvas for your methods figure or graphical abstract.

TechniqueXRD · XPS · BET · SEM · TEM · NMR

Characterisation techniques

Fifteen materials characterisation techniques explained with sources: XRD, XPS, BET, SEM, TEM, AFM, NMR, FTIR, Raman, TGA, UV–vis, DLS, CV, EIS and ICP-MS.

XRD: Crystal structure, phase and crystallite size (nλ = 2d sin θ)

Techniquenλ = 2d sin θ

X-ray diffraction (XRD)

X-ray diffraction explained: Bragg’s law, how to read an XRD pattern, phase identification, Scherrer crystallite size, Rietveld refinement and common mistakes.

XPS: Surface elements and chemical states, top ~10 nm (BE = hν − KE)

TechniqueBE = hν − KE

X-ray photoelectron spectroscopy (XPS)

XPS explained: binding energy, 2–10 nm surface sensitivity, survey vs high-resolution spectra, chemical shifts, C 1s charge referencing and depth profiling.

BET: Surface area, pore size and pore volume (N₂ isotherm at 77 K)

TechniqueN₂ isotherm at 77 K

Gas sorption and BET surface area

BET surface area explained: N₂ sorption at 77 K, IUPAC isotherm types, the BET range and Rouquerol criteria, pore size, degassing and limits for MOFs.

SEM: Electron images of surfaces, plus EDS elemental maps (Surface morphology and composition)

TechniqueSurface morphology and composition

Scanning electron microscopy (SEM)

How SEM works: secondary vs backscattered electron images, EDS/EDX elemental analysis, resolution, sample coating, low-vacuum mode and common mistakes.

$TEM: Atomic-scale images and diffraction from thin samples (HAADF intensity ∝ Z²)$

TechniqueHAADF intensity ∝ Z²

Transmission electron microscopy (TEM)

How TEM works: bright field, HRTEM lattice images, SAED diffraction, STEM-HAADF Z-contrast, EDS/EELS, sample thickness and beam damage of MOFs.

AFM: A sharp tip maps surfaces in 3D, in air or liquid (Height, phase and nanoscale forces)

TechniqueHeight, phase and nanoscale forces

Atomic force microscopy (AFM)

How AFM works: tip, cantilever and laser deflection, contact vs tapping mode, measuring 2D flake thickness from height profiles, and common AFM artefacts.

NMR: Atomic-level structure from nuclear spins (Chemical shift δ (ppm))

TechniqueChemical shift δ (ppm)

Nuclear magnetic resonance (NMR) spectroscopy

NMR spectroscopy explained: nuclear spins in a magnetic field, chemical shift in ppm, ¹H and ¹³C, coupling, integration, solid-state MAS and MOF digestion NMR.

FTIR: Functional groups from infrared absorption (A = log₁₀(I₀/I))

TechniqueA = log₁₀(I₀/I)

Fourier-transform infrared (FTIR) spectroscopy

FTIR spectroscopy explained: infrared absorption by bond vibrations, the interferometer and Fourier transform, wavenumber regions, ATR and reading bands.

Raman: Vibrations from inelastically scattered laser light (Raman shift Δν̃ = ν̃₀ − ν̃ₛ (cm⁻¹))

TechniqueRaman shift Δν̃ = ν̃₀ − ν̃ₛ (cm⁻¹)

Raman spectroscopy

Raman spectroscopy explained: inelastic laser scattering, Raman shift, Stokes lines, IR complementarity, graphene D, G and 2D bands, lasers, fluorescence.

TGA / DSC: Thermal stability, composition and phase transitions (Mass and heat flow vs temperature)

TechniqueMass and heat flow vs temperature

TGA and DSC (thermal analysis)

TGA and DSC explained: mass loss and DTG vs temperature, atmosphere, MOF thermal stability, and glass transition, melting and crystallisation in DSC.

UV–vis: Absorbance, concentration and optical band gap (A = εcl)

TechniqueA = εcl

UV–vis spectroscopy

UV–vis spectroscopy explained: absorbance and the Beer–Lambert law, band gap from a Tauc plot, diffuse reflectance for powders and gold plasmon bands.

DLS / ζ: Hydrodynamic size and surface charge of particles (D = kT / 6πηr)

TechniqueD = kT / 6πηr

DLS and zeta potential

DLS and zeta potential explained: Brownian motion, Stokes–Einstein hydrodynamic size, intensity vs number distributions, PDI and colloidal stability.

CV: Current vs potential: redox peaks and kinetics (ΔEp ≈ 59/n mV (reversible))

TechniqueΔEp ≈ 59/n mV (reversible)

Cyclic voltammetry (CV)

Cyclic voltammetry explained: three-electrode cell, scan rate, redox peaks, 59/n mV reversibility, Randles–Ševčík, RHE conversion, ECSA and Tafel pitfalls.

EIS: Resistances, capacitances and diffusion vs frequency (Z(ω) = Z′ + jZ″)

TechniqueZ(ω) = Z′ + jZ″

Electrochemical impedance spectroscopy (EIS)

EIS explained: small AC perturbation, Nyquist and Bode plots, Randles circuit, charge-transfer resistance, Warburg diffusion, batteries and catalysts.

ICP-MS: Argon plasma elemental and isotopic analysis (Elemental content down to ng L⁻¹)

TechniqueElemental content down to ng L⁻¹

ICP-MS and ICP-OES

ICP-MS and ICP-OES explained: argon plasma, detection limits, acid digestion, interferences, single-particle ICP-MS and metal content of MOFs.