Determination of non-traditional intrinsic fluorescence (NTIF) emission sites in 1-(4-carbomethoxypyrrolidone)-PAMAM dendrimers using CNDP-based quenching studies

  • Malgorzata Konopka
  • Anna Janaszewska
  • Kayla A.M. Johnson
  • David Hedstrand
  • Donald A. Tomalia
  • Barbara Klajnert-MaculewiczEmail author
Research Paper
Part of the following topical collections:
  1. Unifying Concepts for Nanoscience and Nanosystems: 20th Anniversary Issue


A unique photoluminescent phenomenon producing inexplicable, blue emissions [λEx = 365 nm; λEm = 460 nm] in the absence of traditional aromatic fluorophores has been observed in a variety of surface functionalized poly(amidoamine) (PAMAM) dendrimers over the past two decades. This emission phenomenon, referred to as non-traditional intrinsic fluorescence (NTIF), originates from the intra-molecular clustering of electron-rich sub-fluorophores (i.e., tertiary amines and/or amido groups) residing in the interior of all PAMAM dendrimers. The intra-molecular clustering of these interior sub-fluorophores is hypothesized to account for the modest but reproducible, blue emissions observed for a variety of dendrimer surface moieties (i.e., –OH, –CO2H, and –NH2). Unexpectedly, a simple, one-step conversion of amine-terminated PAMAM dendrimers to 1-(4-carbomethyoxy) pyrrolidone-terminated dendrimers (4-CMP) was found to produce a 50-fold increase in blue NTIF emission compared to other surface moieties. In an effort to understand this new enhanced emission property, critical nanoscale design parameter (CNDP)-directed quenching experiments were devised to probe the increased NTIF emissions. Was it originating from the interior sub-fluorophoric tertiary amine/amido moieties or from the surface-attached, sub-fluorophoric pyrrolidone amido groups or both? Four generations of 4-CMP PAMAM dendrimers were examined. Two classical quenchers, namely, potassium iodide and acrylamide were selected to probe surface versus interior domains, respectively, as a function of predictable CNDPs associated with generation levels. With increasing dendrimer generation, quencher penetration into the dendrimer interior is impeded due to CNDP-directed generational congestion. Stern-Volmer plots for each quencher, as a function of generation, exhibited appropriate linear or non-linear correlations that corroborated behavior expected for two distinct region-specific emission sites.


PAMAM dendrimers Intrinsic emission Auto-fluorescence Non-traditional fluorescence (NTIF) Unconventional fluorescence NTIF quenching 



The work was sponsored by the Polish National Science Centre (Project Harmonia “Intrinsically fluorescent dendrimers – spectrofluorimetric and cell biology studies” UMO-2014/14/M/NZ3/00498).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

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Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Department of General Biophysics, Faculty of Biology and Environmental ProtectionUniversity of LodzLodzPoland
  2. 2.NanoSynthons LCCMt. PleasantUSA
  3. 3.Department of ChemistryUniversity of PennsylvaniaPhiladelphiaUSA
  4. 4.Department of PhysicsVirginia Commonwealth UniversityRichmondUSA

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