Concentration of colloidal silica suspensions using fluorescence spectroscopy

Yeomin Yoon, Richard M. Lueptow

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


A simple detection method based on fluorescence excitation-emission spectroscopy has been developed to quantify the concentration of Ludox colloidal silica nanoparticles having diameters ranging from 7 to 22 nm. The technique works for suspensions of nominally negatively (SM30, LS, and TM40) and positively (CL) charged colloid silica particles. Without pretreatment, the method detection limits are 1.4 mg/L SiO2 for CL (12 nm) and TM40 (22 nm) suspensions and 12 mg/L SiO2 for SM30 (7 nm) and LS (12 nm) suspensions at an excitation wavelength of 308 nm and an emission wavelength of 318 nm. The fluorescence intensities of all the colloidal silica particle suspensions are linear (R2 > 0.98) with concentration in the range of 0-300 mg/L SiO2. The fluorescence intensity of the negatively charged particle suspensions is constant between pH 3 and 9. The fluorescence intensity of suspensions of particles that are nominally positively charged is constant above pH 5.5, where the particles become negatively charged.

Original languageEnglish
Pages (from-to)107-110
Number of pages4
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Issue number1-3
StatePublished - 5 Apr 2006

Bibliographical note

Funding Information:
This work was supported by NASA. The authors would also like to thank Dr. Mario Esparza for fluorescence EEM analyses at Arizona State University.


  • Fluorescence spectroscopy
  • Ludox colloidal silica particle
  • Nanoparticle suspension
  • Scattering
  • Zeta potential


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