Left: Schematic of the coupling of photonic crystal effect and multiple-beam interference in the CPhCs E-F-E double heterostructure; Middle and Right: Illustration and SEM image of an E-F-E double heterostructure (Scale bar is 1 μm).
Researchers report breakthrough due to novel and multi-layer colloidal photonic crystal structure. It could drive the next advances in sensor technology, energy saving and harvesting, lasers and optoelectronics. According to Dr Li, the researchers discovered that a double heterostructure tri-layer CPhC – with the stopband of top and bottom layers overlapping the excitation wavelength, a middle CPhC layer in resonance with the emission wavelength, and a thickness supporting constructive multiple beam interference for excitation light – resulted in a 1000X fluorescence enhancement in an all-polymer structure compared to that achieved by the same amount of dyes on glass substrate.
(a) The fluorescence spectra double heterostructure E-(CDs@F)-E, heterostructure of E-CDs@F, and single monolithic (CDs@F), control is CDs infiltrated into the amorphous PS structure. (b) FL enhancement factor for all samples, measured as the fluorescence intensity ratio between the sample and the control. (c) concentration-dependent FL linear response of E-(CDs@F)-E film sensor by of Hg(II) compared to concentration-dependent FL linear response of CDs. (d) Reversible changes of the FL intensities of the film sensor when immersed in the solution of 1.0 nM Hg2+ and 2 mM EDTA alternately.
“Furthermore, we found that the enhancement of fluorescence intensity due to the double heterostructure is almost 6X that of monolithic CPhCs,” says Dr Li. “What is even more intriguing is that the emission lifetime constant has been shortened by fourfold.”
Besides highly effective performance in ultra-sensitive sensing – with multiple functions including signal enhancement, ease in immobilisation and protection for sensing agents – the research presents evidence of significant improvements in energy efficiency and flexibility for lighting devices.
“By using our double heterostructure CPhCs, we can give LEDs a significant increase in energy efficiency and flexibility in colour tuning and colour mixing,” says Dr Li. In fluorescence-based sensing technologies, improving signal to noise ratio is of paramount significance for improving sensitivity and reliability.
“Colloidal photonic crystals can be conveniently made into array systems in mass production fashion, for example by inkjet printing method or by pintool plotter,” says Dr Li. Both materials and fabrication methods are inexpensive and scalable.” http://www.nature.com/articles/srep14439 http://www.eurekalert.org/pub_releases/2015-09/gu-cct092915.php
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