Ingrid T. Weber

High photoluminescent metal-organic frameworks as optical markers for the identification of gunshot residues.

Gunshot residue (GSR) are solid particles produced when a firearm is discharged, and its detection is important evidence in forensic investigations. Currently, scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) is the standard technique adopted for the analysis and identification of GSR; however, this methodology is inefficient for lead-free ammunition. Herein, we report the inclusion of high photoluminescent metal-organic frameworks in ammunition to allow for the visual detection of GSR. The tests indicated that marked GSR is easily visible in proportions above 5.0 wt %. A total of 1 g of marker suffices to tag 100 0.38 mm bullets or 62 0.40 mm bullets.

Up-conversion properties of lanthanide-organic frameworks and how to track ammunitions using these materials

This manuscript reports the first example of up-conversion properties involving Yb3+ and Tb3+ ions in five isostructural Lanthanide-Organic Frameworks (LnOFs), herein designated as UCMarker-1 to UCMarker-5, respectively, and their application as optical probes for the identification of gunshot residues (GSRs) and the ammunition encryption procedure. The excitation of the Yb3+ 2F7/2 ↔ 2F5/2 transition (980 nm) at room temperature leads to visible up-conversion (UC) emission of Tb3+ 5D4 → 7FJ. The GSR and lead-free primer residues are easily identified upon UV radiation (λ = 254 nm). These results prove that the exploration of LnOFs to identify GSR is attractive for the identification of ammunition origins or caliber recognition.

Controlling the energy transfer in lanthanide–organic frameworks for the production of white-light emitting materials

Visible color tunable and white-light emitting Ln-MOFs were obtained via layer-by-layer epitaxial growth of different [Ln2(Mell)(H2O)8] compounds, where Mell is mellitate anion and Ln = Eu3+, Tb3+ and Gd3+. The RGB-MOF, RBG-MOF, BRG-MOF and BGR-MOF materials exhibit white-light emission and CIE coordinates (0.337, 0.336), (0.339, 0.330), (0.338, 0.337) and (0.333, 0.336), upon excitation at 361, 347, 378 and 360 nm, respectively. These values are very close to the standardized value of (0.33, 0.33).

Lanthanide-Organic Gels as a Multifunctional Supramolecular Smart Platform

A multifunctional smart supramolecular platform based on a lanthanide-organic hydrogel is presented. This platform, which provides unique biocompatibility and tunable optical properties, is synthesized by a simple, fast, and reproducible eco-friendly microwave-assisted route. Photoluminescent properties enable the production of coated light-emitting diodes (LED), unique luminescent barcodes dependent on the excitation wavelength and thin-films for use in tamper seals. Moreover, piroxicam entrapped in hydrogel acts as a transdermal drug release device efficient in inhibiting edemas as compared to a commercial reference.

Application of the Metal–Organic Framework [Eu(BTC)] as a Luminescent Marker for Gunshot Residues: A Synthesis, Characterization, and Toxicity Study

The 3D metal-organic framework (MOF) [Eu(BTC)] (where BTC = trimesic acid) was synthesized in 20 min by a microwave-assisted hydrothermal method with a yield of 89%. A structural and spectroscopic study, performed by X-ray diffraction, thermogravimetry, and photoluminescence spectroscopy, showed that this framework has high crystallinity, thermal stability, and luminescence. This MOF had a red-orange luminescence when excited with ultraviolet (UV) radiation (λ = 254 nm) and a high potential for use as a luminescent marker for gunshot residues (GSR). When added to 9 mm nontoxic ammunition, it greatly improved quality of the crime scene investigation, allowing for direct visualization of the luminescent GSR on the shooters hand and firearm and at the firing range using only a portable UV lamp. The marked luminescent GSR was easily collected and characterized by nondestructive techniques, including with a Video Spectral Comparator and scanning electron microscopy/energy-dispersive spectroscopy, wherein the presence of Eu3+ ions was confirmed. Furthermore, the oral acute toxicity of this MOF was assessed in adult female Wistar rats using the Organisation for Economic Cooperation and Development 423 guidelines. This study classified the MOF [Eu(BTC)] in a less toxic Globally Harmonized System category (category 5), with a LD50 (lethal dose) of 5000 mg/kg, ensuring a wide security range for its application.

Down- and Up-Conversion Photoluminescence of Carbon-Dots from Brewing Industry Waste: Application in Live Cell-Imaging Experiments

Simple synthetic procedures have been applied to obtain luminescent carbon quantum dots, also referred as C-dots, from an abundant carbon source, that is, from the brewing industry waste. The synthetic procedures have been conducted aiming to investigate the effects of the oxidation stage on the properties of the nanomaterial. C-dots down- and up-conversion properties, as well as their potential for cellular imaging experiments in live (and adhered) cells, are disclosed herein.

Zinc-gallium oxynitride powders: effect of the oxide precursor synthesis route

Zinc-gallium oxynitride powders (ZnGaON) were synthesized by nitridation of ZnGa2O4 oxide precursor obtained by polymeric precursors (PP) and solid state reaction (SSR) methods and the influence of the synthesis route of ZnGa2O4 on the final compound ZnGaON was investigated. Crystalline single phase ZnGa2O4 was obtained at 1100 oC / 12 h by SSR and at 600 oC / 2 h by PP with different grain sizes and specific surface areas according to the synthesis route. After nitridation, ZnGaON oxynitrides with a GaN wurtzite-type structure were obtained in both cases, however at lower temperatures for PP samples. The microstructure and the specific surface area were strongly dependent on the oxide synthesis method and on the nitridation temperature (42 m2g-1 and 5 m2g-1 for PP and SSR oxides treated at 700 °C, respectively). The composition analyses showed a strong loss of Zn for the PP samples, favored by the increase of ammonolysis temperature and by the higher specific surface area.

Influence of Nd Doping on the Properties of SrTiO3 thin Films Synthesized by PLD on Different Substrates

SrTiO3, SrTi0.99Nd0.01O3 and Sr0.99Nd0.01TiO3 thin films were synthesized by pulsed laser deposition at 700 °C on different substrates (silica, R-sapphire, (100) LaAlO3 and (100) MgO). The influence of Nd3+ substitution into the A and B sites of SrTiO3 perovskite on film growth was studied. The films were characterized by X-ray diffraction (θ-2θ, θ- and θ-scans), micro-Raman spectroscopy, UV-Vis spectroscopy and field-emission scanning electron microscopy. All of the films exhibited a (h00) orientation and high-quality epitaxial growth on LaAlOθ. The films grown on MgO, with the exception of the SrTiNd0.01O3 film, also exhibited a (h00) orientation. The polycrystallinity of the SrTi0.99Nd0.01O3 film may be related to the increased lattice distortion when Ti4+ was replaced with Nd3+. A polycrystalline growth was observed for all of the films deposited on silica and R-sapphire, as expected. The Raman results showed that Nd doping led to an increase in the short-range disorder. The morphology strongly depended on the nature of the substrate and on Nd doping, specially in the case of SrTi0.99Nd0.01O3.

Identification of ANFO: Use of luminescent taggants in post-blast residues

This work describes the incorporation of luminescent taggants in cartridges of ammonium nitrate-fuel oil (ANFO) to allow easy identification and collection of post-blast residues. Metal-Organic Frameworks taggants proved to be appropriate for explosive marking when ANFO proportions were above 3.0wt.%. Lanthanide-based light emission enabled in situ retrieval of explosive residues as well as chemical identification, allowing the creation of a coding system using Energy Dispersive Spectroscopy (EDS). The proposed method will accelerate laboratory analysis and support forensic investigations, connecting evidence to suspects and/or to the explosive origin.

Investigation of the use of luminescent markers as gunshot residue indicators

The addition of luminescent markers into ammunition cartridges is an appealing proposal to achieve a greater individual identification of the ammunition. The lanthanide elements present in these luminescent materials act as characteristic chemical markers that, also, offer the great benefit of making gunshot residues (GSR) collection easier. Although the use of luminescent markers offers numerous advantages, and can be a reliable future option in the cartridge ammunition market, little or nothing is known about the interaction of the marker with the ammunition compounds after the shot. For the forensic laboratories, it is of utmost importance to anticipate the commercialization of tagged luminescent ammunition by knowing the type of particles produced after the discharge. That is, to investigate if markers merge with GSR to form single particles or, on the contrary, they form individual particles that travel separately from the GSR particles. In this work, conventional ammunition cartridges tagged with two types of luminescent markers were shot. Then, the particles produced were visualized under UV light on the floor, clothing targets and the shooter. The luminescent particles spread over the floor determined the shooter position and the bullet trajectory. The illumination of the shot targets allows the visualization of the GSR patterns only using a portable UV lamp, avoiding the use of colorimetric test. The GSR particles were collected and subjected to SEM-EDX and Raman spectroscopy analysis to get information about their inorganic and organic composition. The results indicated that part of the marker and the GSR merge and travel together. With this, particles composed by the marker and propellant organic compounds can be identified by Raman spectroscopy, and the unequivocal identification of the GSR and the marker can be achieved by SEM-EDX. Consequently, the luminescent particles detected under UV light improve the evidence collection and offer information about the GSR and the marker. Additionally, this study support the use of luminescent ammunition to study, for example, the transfer or persistence of GSR.