Colloidal Quantum Dots for Cost-effective, Miniaturized, and Simple Spectrometers.

Abstract

According to a market report published by Transparency Market Research (1), the global spectrometry market was valued at $12.2 billion in 2013 and is estimated to reach $19.6 billion by 2020. The market can be divided into 3 categories: atomic spectrometry, mass spectrometry, and molecular spectrometry. As of 2013, molecular spectrometry reportedly had the highest market share of the 3 spectrometry techniques. Not surprisingly, there has been a large surge in interest for handheld and portable molecular spectrometers for consumers, food suppliers, pharmaceutical companies, and the military, with a vast range of applications. Handheld and miniaturized molecular spectrometers have primarily delivered capabilities for color measurement or spectrometry in the ultraviolet-visible (UV-VIS),3 near infrared, or infrared (IR) ranges, but several factors can limit their performance. In particular, the resolution and spectral range of the spectrometer are highly dependent on the inherent design. To date, most spectrometers use interference filters and interferometric optics as the basis of operation. However, a recent paper in Nature Letters describes a miniaturized spectrometer that uses the absorption spectrum of colloidal quantum dots (CQDs) overlaid on a charge-coupled device (CCD) detector as an alternative to interferometric techniques (2). The CQD spectrometer exploits the absorption spectrum of 195 different types of quantum dots to cover a spectral range of 300 nm (390–690 nm). The performance of the CQD spectrometer was demonstrated through its ability to measure shifts in spectral peaks as small as 1 nm. The spectral resolving capability between 2 peaks in the ideal case (no measurement or instrument noise present in system) is 3.2 nm. The CQD materials comprised aliquots of CdS and CdSe preparations, which were converted into broadband wavelength filters by quenching the fluorescent emission of the CQDs through …