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We introduce a new latent fingermark (LFM) development method, where compounds showing long lifetime luminescence are generated in situ by the reactions of Eu(TTA) 3 (H 2 O) 2 with LFM components. Until now, time-gated imaging could not be used to develop LFM on porous surfaces due to the difficulties with selective binding of the developing agents to the fingermark ridges. The nature of the interactions of Eu(TTA) 3 (H 2 O) 2 with the LFM material has been investigated for three model compounds commonly found in the LFM composition-oleic acid, l-serine, and squalene. The LFMs developed with the europium β-diketonate complex have been successfully photographed using a time-gated imaging scheme. The presented new approach has been demonstrated to give similar or better results than developing agents commonly used for paper samples (ninhydrin and 1,2-indanedione). Moreover, contrary to the methods mentioned above, the new approach allows for the development of amino acid-poor LFM on paper.

To obtain chitosan (CTS) with narrower molecular weight distribution, CTS with weight-average molecular weight (M W ) of 197.30 kDa was first metal complexed and then degraded into five CTSs with M W of 107.90, 56.48, 10.40, 5.67 (CTS-4) and 3.66 kDa. Decrease of M W did not cause a significant change in chemical structure of the residue CTS, but the crystal structure was transformed significantly. The moisture retention increased firstly and then decreased as the M W of CTS decreased. CTS-4 was superior to CTSs with other M W and propylene glycol in terms of the moisture retention. The lower water activity and increase of net isosteric heat were observed in CTS-4, which was due to the migration of immobilized water to a bound-state caused by mounting newly formed chain-end hydrophilic groups per unit weight. CTS-4 could effectively improve moisture retention, showing a potential to substitute commonly used humectant such as propylene glycol., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Cobalt(ii) phthalocyanine (CoPc) was suspended in aqueous medium and the colloidal system was used as catalyst for the electrochemical determination of hydrogen peroxide on paper-based electrodes modified with carbon nanomaterials. H 2 O 2 was oxidised at 0.275 V vs. Ag pseudoreference electrode. This system was adapted to develop a glucose sensor with glucose oxidase immobilized on the cellulose electrode. CoPc suspended nanoparticles acted as nanoenzyme mimicking peroxidase activity and were combined with different carbon nanomaterials to form hybrids with optimised catalytic performance. GO-CoPc paper-based electrodes yielded the best results with a linear range of ∼12 μM to 49 mM for H 2 O 2 and 0.1 mM to 1 mM for glucose. Glucose was determined in physiological serum and juice samples with recoveries of 93.3 and 94.2% respectively. CoPc could replace HRP for the catalytic sensing of H 2 O 2 , without the need to be dissolved. This material can be used in situ in a simple protocol with other nanomaterials for electrode modification. The sensor described has the advantage of easy preparation, using the catalyst in colloidal form, long term stability, and versatility to be adapted to other low cost and disposable enzymatic systems.

We introduce for the first time a paper-based analytical device (PAD) for the non-enzymatic detection of glucose by modifying a screen-printed carbon electrode with cobalt phthalocyanine, graphene and an ionic liquid (CoPc/G/IL/SPCE). The modifying composite was characterized by UV-visible spectroscopy, energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The disposable devices show excellent conductivity and fast electron transfer kinetics. The results demonstrated that the modified electrode on PADs had excellent electrocatalytic activity towards the oxidation of glucose with NaOH as supporting electrolyte (0.1M). The oxidation potential of glucose was negatively shifted to 0.64V vs. the screen-printed carbon pseudo-reference electrode. The paper-based sensor comprised a wide linear concentration range for glucose, from 0.01 to 1.3mM and 1.3-5.0mM for low and high concentration of glucose assay, respectively, with a detection limit of 0.67µM (S/N = 3). Additionally, the PADs were applied to quantify glucose in honey, white wine and human serum. The disposable, efficient, sensitive and low-cost non-enzymatic PAD has great potential for the development of point-of-care testing (POCT) devices that can be applied in healthcare monitoring., (Copyright © 2017 Elsevier B.V. All rights reserved.)

There is an ongoing need for explosive detection strategies to uncover threats to human security including illegal transport and terrorist activities. The widespread military use of the explosive trinitrotoluene (TNT) for landmines poses another particular threat to human health in the form of contamination of the surrounding environment and groundwater. The detection of explosives, particularly at low picogram levels, by using a molecular sensor is seen as an important challenge. Herein, we report on the use of a fluorescent metal-organic framework hydrogel that exhibits a higher detection capability for TNT in the gel state compared with that in the solution state. A portable sensor prepared from filter paper coated by the hydrogel was able to detect TNT at the picogram level with a detection limit of 1.82 ppt (parts per trillon). Our results present a simple and new means to provide selective detection of TNT on a surface or in aqueous solution, as afforded by the unique molecular packing through the metal-organic framework structure in the gel formation and the associated photophysical properties. Furthermore, the rheological properties of the MOF-based gel were similar to those of a typical hydrogel., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Moolooite (copper oxalate), a very rare compound, was found as a degradation product from the decay of malachite in several specimens of Cultural Heritage studied. Computer simulations, based on heterogeneous chemical equilibria, support the transformation of malachite to moolooite through the intermediate copper basic sulfates or copper basic chlorides, depending on the presence of available free sulfate or chloride anions in the chemical system. Raman and X-ray fluorescence spectral evidence found during the analysis of the three case studies investigated supported the model predictions. According to the study, the presence of lichens and other microorganisms might be responsible for the decay phenomena. This work tries to highlight the importance of biological attack on specimens belonging to Cultural Heritage and to demonstrate the consequences of oxalic acid, excreted by some of these microorganisms, on the conservation and preservation of artwork.

The utilization of the lanthanide shift reagent tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III) [Eu(fod)3] as a simple one-step reagent for the luminescent visualization of latent fingerprints has been investigated. UV excitation of Eu(fod)3-treated prints, achieved by using a hand-held UV lamp or a Polilight, results in an orange emission at 614 nm. Time-resolved imaging is not required for visualization. Visualization of latent fingerprints on paper under the conditions used, although good, was found to be inferior to that obtained by standard DFO (1,8-diazafluoren-9-one) treatment, whereas visualization of prints obtained on aluminum drink cans and galvanized iron proved superior to that obtained by Superglue/panacryl treatment. Eu(fod)3 treatment can also be used first without compromising subsequent ninhydrin or DFO treatment, making it a 'nothing-to-lose" reagent.