Nanomaterials: Making a Bluer Light

NanolightThere are reams of R&D articles on nanomaterials nowadays, and it never surprizes me that there a mention of a rare metal or graphite/grapheme connection. Today is no different, A couple of weeks ago, ScienceDaily (Apr. 12th) reported on a new design for nanoparticles that absorb low-energy light and emit high-energy light may find use in biological imaging.

The article notes that the light that a luminescent particle emits is usually less energetic than the light that it absorbs. However, some applications require the emitted light to be more energetic, and as such, require some form of ‘upconversion’. Apparently only a small handful of materials show this upconversion process… that is until now ! (Aha — the rare metal connection!)

A team of researchers at Singapore’s A*STAR Institute of Materials Research and Engineering (IMRE) have succeeded in expanding the list of upconversion materials, easing the path to new applications

As described in ScienceDaily, “Traditional upconversion particles are distinguished by their evenly-spaced or 'ladder-like' energy levels which their internal electrons can take on. The even spacings allow an electron to be promoted up in energy many times consecutively, by absorbing many photons of the same color. When an electron that has been promoted to a high energy finally relaxes back to the lowest-energy state, it emits a photon which is more energetic than the photons that excited it to begin with.” (Whew!)

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The Singaporean Team tried doping nanoparticles with elements from the lanthanide (rare earth) group of the periodic table and which are capable of upconversion. These materials were thought to be valuable in biological imaging because their high-energy emission can be clearly distinguished from background noise. There testing showed that only three elements from the lanthanide series are efficient at upconversion: erbium, thulium, and holmium. Not a long list, because apparently there are two simultaneous requirements that an upconversion particle – to exhibit a ladder-like electronic energy structure and also show efficient emission.

This prompted the Team to seek a broader solution, ultimately using different lanthanides to perform different stages of the upconversion process. Sensitizer elements absorb incident light, and transfer the absorbed energy to nearby accumulators, whose electrons rise to high energy levels. Then, the energy stored in accumulators transfers by hopping through many migrators, until an activator is reached. Finally, the activator releases a high-energy photon.

By assigning different elements to each of these four functions, the researchers were able to ease the requirements on any individual element. Ultimately the team observed a spectrum of colors from the upconverted emission of europium, terbium, dysprosium and samarium.

AStFor those of you who aren’t familiar with this IMRE — The Institute of Materials Research and Engineering is a research institute of the Science and Engineering Research Council (SERC) under Agency for Science, Technology and Research (A*STAR). The Institute has capabilities in materials analysis & characterisation, design & growth, patterning & fabrication, and synthesis & integration. IMRE conducts a wide range of research, which includes novel materials for organic solar cells, photovoltaics, printed electronics, catalysis, bio-mimetics, microfluidics, quantum dots, heterostructures, sustainable materials, and atom technology… many of which also have rare metal connections.For those of you who aren’t familiar with this IMRE — The Institute of Materials Research and Engineering is a research institute of the Science and Engineering Research Council (SERC) under Agency for Science, Technology and Research (A*STAR). The Institute has capabilities in materials analysis & characterisation, design & growth, patterning & fabrication, and synthesis & integration. IMRE conducts a wide range of research, which includes novel materials for organic solar cells, photovoltaics, printed electronics, catalysis, bio-mimetics, microfluidics, quantum dots, heterostructures, sustainable materials, and atom technology… many of which also have rare metal connections.

The original ScienceDaily article can be found at http://www.sciencedaily.com/releases/2012/04/120412105102.htm

Until soon… Ian


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