Vicki L. Colvin

Toward open source nano: Arsenic removal and alternative models of technology transfer

In the wake of growing pressures to make scholarly knowledge commercially relevant via translation into intellectual property, various techno-scientific communities have mobilized to create open access/open source experiments. These efforts are based on the ideas and success of free and open source software, and generally try to exploit two salient features: increased openness and circulation, and distributed collective innovation. Transferring these ideas from software to science often involves unforeseen challenges, one of which is that these movements can be deemed, often incorrectly, as heretical by university administrators and technology transfer officers who valorize metrics such as number of patents filed and granted, spin-off companies created, and revenue generated. In this paper, we discuss nascent efforts to foster an open source movement in nanotechnology and provide an illustrative case of an arsenic removal invention. We discuss challenges facing the open source nano movement that include making a technology widely accessible and the associated politics of metrics.

Engineered superparamagnetic iron oxide nanoparticles for ultra-enhanced uranium separation and sensing

Rapid separation and analysis of radionuclides in the environment remains a challenge despite broad needs, particularly for ultra-sensitive field detection. Ionizing radiation detection/counting can be limited by sample matrix shielding and long integration times, while more sensitive spectrometry requires extensive sample preparation and advanced instrumentation. In this work we have designed, synthesized, and demonstrated optimized iron oxide nanoparticles (IONPs) for low-energy, high-efficiency separation and concentration for ultra low-level uranium (as a model actinide) sensing in dilute (environmental) applications. Monodispersed single crystalline, IONPs with an ordered, oleic acid bilayer coating, are demonstrated to bind ca. 50% wt U/wt Fe, under optimal conditions, which is the highest reported for any iron-based sorbent materials to date. Superparamagnetic material properties allow for subsequent low-field magnetic separations from heterogeneous and relatively large (dilute) aqueous volumes resulting in highly concentrated residues. Through a final filtration step, high particle (aqueous) stability gives rise to self-assembling, homogenous, sub-micron films, arranged to minimize α-particle self-shielding, thus allowing for optimized sensitivity/detection with a handheld Gieger counter. Taken together, we demonstrate a ca. 10 000-fold increase in uranium detection sensitivity when compared to commercially available nanoscale IONPs (combining sorption and detection/counting enhancements). Lastly, these advantages are demonstrated for real world samples.

White light-emitting diodes of high color rendering index with polymer dot phosphors

Nowadays the yellow emissive YAG:Ce phosphors play an important role in fabricating white light-emitting diodes (WLEDs). However, they are deficient in red emission so we proposed polymer dot phosphors to compensate this poor photometric property. The polymer dot phosphors exhibited broad emission bands under excitation of a blue LED chip with weak reabsorption. We demonstrated hybrid white light-emitting diodes with commendable color rendering index (85–95), widely variable color temperatures (3050–7295 K) and high luminous efficacy (72–80 lm W−1 operated at 20 mA) by combining green and red emitting polymer dots on YAG:Ce-based WLEDs. The optical properties suggest the polymer dot phosphors are the suitable color converting materials, which may enable their application in WLED lighting.

PbS Capped CsPbI 3 Nanocrystals for Efficientand Stable Light-Emitting Devices Using p – i – n Structures

Cesium lead halide perovskite nanocrystals (NCs) have unique optical properties such as high color purity and high photoluminescence (PL) efficiency. However, the external quantum efficiency (EQE) of the corresponding light-emitting diodes (LEDs) is low, primarily as a result of the NC surface defects. Here, we report a method to reduce the surface defects by capping CsPbI3 NCs with PbS. This passivation significantly enhanced the PL efficiency, reduced the Stokes shift, narrowed the PL bandwidth, and increased the stability of CsPbI3 NCs. At the same time, CsPbI3 NC films switched from n-type behavior to nearly ambipolar by PbS capping, which allowed us to fabricate electroluminescence LEDs using p–i–n structures. The thus-fabricated LEDs exhibited dramatically improved storage and operation stability, and an EQE of 11.8%. These results suggest that, with a suitable surface passivation strategy, the perovskite NCs are promising for next-generation LED and display applications.