The goal of this work was to study the effect of alkaline pretreatments on the thermal decomposition and composition of industrial hemp (Cannabis sativa L.) samples. Thermogravimetric/mass spectrometric measurements (TG/MS) have been performed, on untreated, hot water washed and alkali treated hemp samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. Principal Component Analysis (PCA) has been used to find statistical correlations between the data. Correlations have been obtained between the parameters of the thermal decomposition and the alkali ion content as well as the altered chemical structure of the samples. The differences in the thermal behaviour of the samples are explained by the different K + and Na + content and the changed structure of the hemicellulose component of the samples due to the pretreatments. The more alkali ions remain in the hemp samples after the alkali treatment, the more ash, char and lower molecular products are formed during thermal decomposition.
The protein mediated approach is a common method for the synthesis of photoluminescent gold quantum clusters (GQCs), where proteins, acting as reducing and stabilizing agents, react with gold salts through cysteine residues. For the better understanding of the phenomenon, the aqueous phase reaction of HAuCl4 and L-cysteine has been investigated at the supramolecular level by various experimental techniques and molecular mechanics simulations. We have observed the formation of a novel photoluminescent product, (AuCys)n β , which shows emission in the orange region of the spectrum. Small-and wide-angle X-ray scattering (SWAXS) measurements have revealed the presence of nanosized lamellae, which have an internal multilayer superlattice structure with a characteristic periodic distance of 1.3 nm. Based on the results, the layers are built up by zigzag shaped (AuCys)n polymer chains connected through aurophilic bonds. The aurophilic network is stabilized via salt bridges and hydrogen bonds, which are also responsible for the interlayer interactions. Here, the evolution of the multilayer structure has been monitored by the combined application of photoluminescence spectroscopy and time-resolved SAXS. It has been concluded that there is a strong correlation between the emission and the scattering intensity, which suggests that the two-and three-dimensional aggregation of the building blocks to form sheets and multilayers are simultaneous processes. Furthermore, we have revealed that the formation and behavior of (AuCys)n β show significant differences to that of Au-L-glutathione compounds desrcibed earlier despite the similarity of L-cysteine and L-glutathione. These results evidence that L-cysteine and gold species form building blocks that can be applied expansively in supramolecular and cluster chemistry.
A widely used oxidizing agent in organic chemistry with an assumed structure of '[Ag(py)2]MnO4' and its perchlorate and perrhenate analogues are studied. Their synthesis in pure form is challenging. In order to clarify the chemical nature of known compounds and find routes to new derivatives, a systematic study is presented for the synthesis of [Ag(py)n]XO4 (X= Mn, Cl, Re, n=2-4) complexes. Ten complexes including four new derivatives, namely [Ag(py)4]MnO4, [Ag(py)4]MnO4•4[Ag(py)2]MnO4, [Ag(py)2]ClO4•0.5py, and [Ag(py)2]ReO4 are synthesized and characterized. The chemical identity of 'Ag(py)2MnO4' is also clarified. A novel route to prepare [Ag(py)2]MnO4 is developed. The reaction of AgXO4 salts with neat pyridine followed by various crystallization techniques is used to prepare [Ag(py)2]XO4, [Ag(py)4]XO4, [Ag(py)4]XO4•4[Ag(py)2]XO4 and [Ag(py)2]XO4•0.5py (X=Cl, Mn), complexes. The solid phase structure of [Ag(py)2]MnO4•0.5py is determined (a=19.410 Å, b=7.788 Å, c=21.177 Å, =104.20°, C2/c (15), Z=4(8)). [Ag(py)2] + cations in the crystal form dimeric units where silver ions are connected by oxygen atoms of two MnO4anions. The Ag…Ag distance is indicative of argentophilic interaction. The pyridine ring … interactions contribute to the stability of the crystal lattice.
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