# Quantitative size-dependent structure and strain determination of CdSe nanoparticles using atomic pair distribution function analysis

## TL;DR

This study uses atomic pair distribution function analysis to determine the size-dependent structure and strain in CdSe nanoparticles, revealing core structure, fault density, and size-related strain with high precision.

## Contribution

It introduces a quantitative PDF method for analyzing the structure and strain in very small CdSe nanoparticles, including fault density and core size.

## Key findings

- Core structure is wurtzite with stacking faults (~50%)
- Core diameter matches standard measurements, indicating minimal surface amorphous regions
- Smaller particles exhibit increased compressive strain in Cd-Se bonds

## Abstract

The size-dependent structure of CdSe nanoparticles, with diameters ranging from 2 to 4 nm, has been studied using the atomic pair distribution function (PDF) method. The core structure of the measured CdSe nanoparticles can be described in terms of the wurtzite atomic structure with extensive stacking faults. The density of faults in the nanoparticles ~50% . The diameter of the core region was extracted directly from the PDF data and is in good agreement with the diameter obtained from standard characterization methods suggesting that there is little surface amorphous region. A compressive strain was measured in the Cd-Se bond length that increases with decreasing particle size being 0.5% with respect to bulk CdSe for the 2 nm diameter particles. This study demonstrates the size-dependent quantitative structural information that can be obtained even from very small nanoparticles using the PDF approach.