A user-friendly set of computer-aided design (CAD) models and stereolithography (STL) files is reported for the production of simple and inexpensive 3D printed colorimeters. The designs shared here allow educators to provide active learners with tools for constructing instruments in activities aimed at exploring the technology and fundamental principles related to quantitative analysis. While previous efforts focused on fabricating inexpensive instruments from building blocks and other household items, 3D printing transcends the limitations of conventional tooling. The digital models described here are flexible in design, printed quickly, and each requires less than a dollar's worth of plastic filament. These designs are compatible with simple CAD software, such as Inventor Professional and Tinkercad, commonly available to educators and students. With the use of programs of this type, CAD files are easily modified in order to produce customized models for exploring a variety of concepts inaccessible to more conventional instruments. Developed with novice 3D printer users in mind, comprehensive slicer settings are provided to assist educators in obtaining reliable results. Once printed, the resulting colorimeter instruments perform very well when compared to commercially available spectrophotometers.
We describe a novel manifestation of rigidochromic behavior in a series of tetranuclear Cu(I)−pyrazolate (Cu 4 pz 4 ) macrocycles, with implications for solid-state luminescence at deep-blue wavelengths (<460 nm). The Cu 4 pz 4 emissions are remarkably sensitive to structural effects far from the luminescent core: when 3,5-di-tert-butylpyrazoles are used as bridging ligands, adding a C4 substituent can induce a blue shift of more than 100 nm. X-ray crystal and computational analyses reveal that C4 units influence the conformational behavior of adjacent tert-butyl groups, with a subsequent impact on the global conformation of the Cu 4 pz 4 complex. Emissions are mediated primarily through a clustercentered triplet ( 3 CC) state; compression of the Cu 4 cluster into a nearly close-packed geometry prevents the reorganization of its excited-state structure and preserves the 3 CC energy at a high level. The remote steric effect may thus offer alternative strategies toward the design of phosphors with rigid excited-state geometries.
The plant hormone ethylene (C2) can induce premature fruit ripening and flower senescence at levels below 1 ppm, which has motivated efforts to develop cost-effective methods for C2 monitoring during the transport and storage of climacteric fruits. Here, we describe a nanocomposite film composed of exfoliated MoS2, single-walled carbon nanotubes (SCNTs), and Cu(I)–tris(mercaptoimidazolyl)borate complexes (Cu–Tm) for real-time detection of C2 at levels down to 100 ppb. A copercolation network of MoS2 and SCNTs was deposited onto interdigitated Ag electrodes printed on plastic substrates and then coated with Cu–Tm with a final conductance in the 0.5 mS range. Reversible changes in relative conductance (−ΔG/G 0) were measured upon C2 exposure with a linear response at sub-ppm levels. The thin-film sensors were highly selective toward C2, and they responded weakly to other volatile organic compounds or water at similar partial pressures. A mechanism is proposed in which Cu–Tm behaves as a chemically sensitive n-type dopant for MoS2, based on spectroscopic characterization and density functional theory modeling. Cu–Tm-coated MoS2/SCNT sensors were also connected to a battery-powered wireless transmitter and used to monitor C2 production from various fruit samples, validating their utility as practical, field-deployable sensors.
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