Enhanced NIR-I Emission from Broadband Water-Dispersible NIR-II Dye-Sensitized Upconversion of Near-Infrared Light


Lanthanide (Ln3+)-doped upconverting nanoparticles (UCNPs) have attracted a great deal of research interest as they possess prominent advantages such as high spatial emission resolution, deep tissue penetration of near-infrared (NIR) excitation light, reduced light scattering and low autofluorescence background signal, among others. Such unique properties are at the core of the widespread applications of UCNPs in solar cells, security inks, biosensing, clinical applications and bioimaging (both in vitro and in vivo), for instance. Yet, some fundamental limitations such as the weak and narrow absorption bands of Ln3+ ions and their low absorption cross-section limit UCNPs in broadly harvesting near NIR light and producing bright upconversion luminescence, thus restricting their scope of utility in a wide range of applications.

To address these limitations, recently, enormous research input has been directed towards the development of NIR dye-sensitized UCNPs as they offer prominent advantages including a broader absorption range and enhanced upconversion efficiency. In most of the literature reports, NIR dyes have been directly anchored onto the surface of UCNPs, leading to the energy transfer across the organic/inorganic interface to the Ln3+ ions doped in UCNPs, thereby improving upconversion efficiency. However, such dye-sensitization processes using UCNPs/pristine organics-soluble dyes are mostly carried out in non-aqueous media and hence is of little use for biological imaging in the NIR-I or NIR-II window.

To overcome this bottle-neck, Prof. Ribeiro’s research group proposed to employ a water-dispersible NIR-II dye (IR-1061) to sensitize core/active shell UCNPs and achieve sufficiently high upconversion quantum efficiency in aqueous media. The core/active shell UCNPs were synthesized following modified high temperature co-precipitation method and the water dispersible dye was prepared using tip-sonication and phase transfer process.

The authors have particularly focused on achieving strong NIR-I emission rather than visible upconversion emission as the latter suffers from limitations of shallow tissue penetration depth, which again is not beneficiary for biological applications.

For this purpose, Pluronic F68-encapsulated water-dispersible IR-1061 dye was coupled with polyethyleneimine (PEI)-coated NaYF4:Tm3+/Yb3+@NaYF4:Yb3+ core/active shell UCNPs based on the electrostatically interactions between negatively charged water-dispersible NIR dyes and positively charged surface of UCNPs.

The authors achieved a 283% enhancement in NIR-I emission (i.e. 800 nm emission of Tm3+ ion) from water-dispersible NIR-II dye-sensitized core/active shell UCNPs via doping of ytterbium ions (Yb3+, 10 mol % optimal) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. Practically, in comparison with the native form of the dye, this water-dispersible dye can also efficiently harvest irradiation energy, which is nonradiatively transferred to Yb3+ ions in the shell (via Forster mechanism) and subsequently to Yb3+ ions in the core. The later sensitizes Tm3+ ions positioned in the core, thus generating upconversion luminescence from the UCNPs. The detailed mechanistic study by Prof. Ribeiro’s research group found an optimal UCNPs/dye ratio of 1/60 for efficient energy transfer between water-dispersible IR-1061 dye and UCNPs.

In their study, the authors demonstrated a detailed characterization of their proposed dye/UCNPs system, highlighting the possible energy transfer mechanism as well as the effect of shell and core configuration and dye-loading on the upconversion response of the system, thus offering an interesting strategy to improve NIR-I emission from core/active shell UCNPs. Such water-dispersible dye/UCNPs system not only possesses greater potential for a broad spectrum of photonic applications but will also pave the way for new biological and medical applications.



About the author

Dr. Chanchal Hazra received his B.Sc and M.Sc in Chemistry from the University of Burdwan, West Bengal, India. He completed his PhD in Chemical Sciences at the Indian Institute of Science Education and Research (IISER)-Kolkata, India in 2015. Since 2016, he is working as FAPESP-Postdoctoral research fellow at the Institute of Chemistry, State University of Sao Paulo (IQ-UNESP), Araraquara, Brazil. His current research is focused on lanthanide-doped down and/or upconverting nanoparticles, multifunctional nanoplatforms, and novel photoactive nano and/micromaterials and exploring them for sensing, bioimaging (or medicinal) and environmental remediation applications.

About the author

Dr. Sajjad Ullah is Assistant Professor in Chemistry at the Institute of Chemical Sciences, University of Peshawar, Pakistan. He received his PhD in Chemistry from University of São Paulo (IQSC, USP), Brazil in 2014 and worked as Postdoctoral Fellow at the Institute of Chemistry of Araraquara, State University of São Paulo (IQ-UNESP), Brazil (2016-2018). He has 11 years of teaching/research experience at five different Public sector Universities of Pakistan and Brazil. His research is focused on the development of novel photoactive materials (nanoparticles, membranes, thin films) for environmental remediation using UV/Vis/NIR radiation.

About the author

York E Serge Correales received his bachelor’s degree in chemistry at the University of Atlantic, Barranquilla, Atlántico, Colombia in 2016. Thereafter, he moved to Institute of Chemistry, Sao Paulo State University (IQ-UNESP), Araraquara, Sao Paulo, Brazil to pursue his Master degree. Before completion his Master degree, because of his outstanding research activity and academic records, in 2018, he achieved the opportunity to carry out his direct-doctoral program (supported by FAPESP, Brazil) under the supervision of Prof. Sidney J. L. Ribeiro in the same institute. His current research interest focuses on lanthanide-doped down and/or upconverting nanoparticles for environmental remediation and biological applications.

About the author

Laís G. Caetano received her bachelor’s degree in Chemistry at the Federal University of Viçosa (UFV-CRP), Rio Paranaíba, Brazil in 2014. Thereafter, she joined at the Institute of Chemistry, São Paulo State University (IQ-UNESP), Araraquara, Brazil and completed her master’s degree in Chemistry in 2016. For her Master’s project she joined Prof. Sidney J.L. Ribeiro’s research group and continuing her PhD in the same group on developing efficient materials of highly stable efficient counter-electrodes for dye sensitized solar cells (DSSC).

About the author

Sidney J.L. Ribeiro- Professor of Inorganic Chemistry at the Institute of Chemistry of the São Paulo State University (UNESP) in Araraquara-SP, Brazil. PhD in Inorganic Chemistry (UNESP-UFPE-1992). Pos-Doc at École Centrale Paris (1994) and CNET-France Telecom (1995) working with transparent glass-ceramics and lasers. Main interests are in Inorganic Chemistry and its implications in Materials Science, Spectroscopy and Education in Chemistry. On-going research projects deal with natural polymers (bacterial cellulose and fibroin), organic-inorganic hybrids, waveguides (optical fibers and thin films), porous materials and luminescent markers for Medicine. Supervisor of 16 PhD thesis, 25 MsC and 18 pos-docs.

Member of the international board of the Journal of Sol-Gel Science and Technology and Journal of Non-Crystalline Solids. Worked as invited researcher at NIRIM – National Institute for Research in Inorganic Materials – Tsukuba, Japão. Worked as visiting Professor at the Univeristy of Trento in Italy, Universities of Angers, Toulouse and Bordeaux in France, University of Aveiro in Portugal and Federal University of Juiz de Fora, Juiz De Fora-MG, Brazil.


Chanchal Hazra, Sajjad Ullah,  York E. Serge Correales, Laís G. Caetano and  Sidney J. L. Ribeiro (2018) . Enhanced NIR-I emission from water-dispersible NIR-II dye-sensitized core/active shell upconverting nanoparticles. Journal of Materials Chemistry C 6, 4777-4785.

Go To Journal of Materials Chemistry C

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