RESEARCH PAPER Layered double hydroxide nanoparticles incorporating terbium: applicability as a fluorescent probe and morphology modifier Anthony W. Musumeci Æ Zhi Ping Xu Æ Suzanne V. Smith Æ Rodney F. Minchin Æ Darren J. Martin Received: 13 May 2008 / Accepted: 18 December 2008 / Published online: 8 January 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Stable and non-invasive fluorescent probes for nanotoxicological investigations are greatly needed to track the fate of nanoparticles in biological systems. The potential for terbium (Tb) to act as a fluorescent probe and its effect on layered double hydroxide (LDH) nanoparticle morphology are presented in this study. Incorporation of Tb during synthesis offers a simple methodology to easily tailor LDH nanoparticle thickness. A three-fold reduction in the average crystallite thickness (from 13 to 4 nm) has been achieved, whilst preferential lateral growth of LDH nanoparticles in the a-b crystal plane has been observed with increasing Tb loadings. Remarkably, Tb–LDH nanoparticles have emitted green fluorescence with a fluorescence quantum yield of 0.044. Keywords Layered double hydroxide  Fluorescent nanoparticles  Morphology modification  Visualization  Instrumentation Introduction Layered double hydroxides (LDHs) are a type of layered material, normally represented by the formula [M 1-x 2? M x 3? (OH) 2 ](A x  yH 2 O), where M 2? and M 3? can be most divalent and trivalent metal ions and A - be any type of anion (Kovanda et al. 2005). Structur- ally, LDHs consist of octahedral brucite-like layers M 2þ 1x M 3þ x OH ð Þ 2   xþ in which M 2? is partially substituted by M 3? to yield a net positive layer charge. Anionic species as well as water molecules (A x  yH 2 O) x- are present between the brucite-like layers, balancing the positive layer charge (Braterman et al. 2004; Kovanda et al. 2005; Xu et al. 2006a, b). In general, phase pure LDH is obtained for x-values between 0.2 and 0.33 (Cavani et al. 1991). Altering the trivalent to divalent metal cation ratio outside these values will result in the formation of other phases, such as hydroxides and mixed metal oxides. The sandwich-like three-dimensional LDH struc- ture is held together primarily by electrostatic interactions and hydrogen bonds between the positive metal-hydroxide layers and interlayer anions (Fig. 1) (Braterman et al. 2004). The thickness of the interlayer region is dependant on the number, size and orientation of interlayer anions in conjunction A. W. Musumeci (&)  Z. P. Xu  D. J. Martin ARC Centre of Excellence for Functional Nanomaterials, Australian Institute for Nanotechnology and Bioengineering, The University of Queensland, Brisbane, QLD, Australia e-mail: a.musumeci@uq.edu.au S. V. Smith ARC Centre of Excellence for Antimatter-Matter Studies, Australian Nuclear Science and Technology Organisation, Menai, NSW, Australia R. F. Minchin School of Biomedical and Medical Science, The University of Queensland, Brisbane, QLD, Australia 123 J Nanopart Res (2010) 12:111–120 DOI 10.1007/s11051-008-9583-9