Analytical characterisation of pigments on pre-Roman pottery by means of spectroscopic techniques Part I: white coloured shards

This paper is part of a systematic archaeometric investigation aimed at the characterisation of the pigments and related materials (ligand, colour substrate) used in decoration of pottery excavated in the archaeological zone of Canosa (Puglia, Italy). Shards found in thirteen different tombs have been analysed; in this paper samples exhibiting a white colouration have been selected. Both surface (XPS) and bulk (FT-IR) spectroscopies were used which gave complementary information and enabled white pigments to be divided into two groups. Moreover, X-ray diffraction was used in some cases to further support some spectral assignments. The molecular specificity of FT-IR, when applied to the analysis of both pigments and ceramic body, allowed the identification of the various constituents and, hence, provided indirect information on the end-use of the original wares. The potential of the combined use of different spectroscopies to obtain valuable information on both painting materials and technical aspects is shown.     

Defect dominated conductivity in Zn3P2

The electrical resistivity and Hall coefficient of Zn₃P₂ have been measured for single crystal and thin polycrystalline film samples which were annealed over a range of equilibrium vapor compositions and temperatures. The room temperature electrical resistivity of single crystal samples annealed at 573 K varied from approximately 10⁵Ω-cm for single crystals heated in equilibrium with zinc to 10 Ω-cm for those annealed in a phosphorus rich ambient. Hall measurements indicate that a variation in carrier concentration is responsible for these changes. The experimentally observed dependence of carrier concentration [h° ], (cm^?3) on phosphorus pressure is given by [h°] = 1.32 · 10¹⁶ [p(P₄)]^0.13 for samples annealed at 573 K. The experimentally determined pressure dependence is in good agreement with a model based on phosphorus interstitials acting as acceptors. The pressure and temperature dependence of the carrier concentration yield the equilibrium constant K_I for the formation of interstitial phosphorus defects according to the reaction

$\text{1}\text{4}\text{P}{}_4\text{→ P′}{}_{\mathrm{i}}\text{+ h°}$

where

$\text{K}{}_{\mathrm{I}}\text{= 10}{}^{\mathrm{42.4\; \pm \; 2}}\text{cm}{}^{\mathrm{?6}}\text{torr}{}^{0.25}\text{[p(P}{}_4\text{)]}{}^{\mathrm{?0.25}}\text{exp(?1.18}\text{ev}\text{kT}\text{)}$

. The accommodation of phosphorus interstitials is discussed in light of the crystal structure of Zn₃P₂.     

Mono-, di-, and trinuclear luminescent silver(I) and gold(I) N-heterocyclic carbene complexes derived from the picolyl-substituted methylimidazolium salt: 1-methyl-3-(2-pyridinylmethyl)-1H-imidazolium tetrafluoroborate

The N-heterocyclic carbene (NHC) precursor, 1-methyl-3-(2-pyridinylmethyl)-1H-imidazolium tetrafluoroborate, [HCH3im(CH2py)]BF4, reacted with AgBF4 in the presence of aqueous NaOH to produce the silver complex [Ag(CH3im(CH2py))2]BF4 (1) which was then reacted with Au(tht)Cl to form the corresponding gold(I) complex, [Au(CH3im(CH2py))2]BF4 (2). Complex 2 reacted with 1 equiv of AgBF4 to produce the mixed-metal species [AuAg(CH3im(CH2py))2](BF4)2 (3). The reaction of 2 with 1 equiv of Au(tht)Cl followed by metathesis with NaBF4 produces the dimetallic gold complex [Au2(CH3im(CH2py))2](BF4)2 (4). The reaction of [Ag(CH3im(CH2py))2]BF4 (1) with 1 equiv of AgBF4 produces the trinuclear [Ag3(CH3im(CH2py))3(NCCH3)2](BF4)3 (5) complex, which appears to dissociate into a dimetallic complex in solution. Complexes 1-5 were characterized by 1H NMR, 13C NMR, UV-vis, luminescence spectroscopy, elemental analysis, mass spectrometry, and X-ray crystallography. The CH3im(CH2py) ligands in 3 are arranged in a head-to-head fashion spanning a Au-Ag separation of 3.0318(5) A with the carbene portion of the ligand remaining coordinated to the Au(I) center. In 4, the ligands are arranged in a head-to-tail fashion with an Au-Au separation of 3.1730(5) A. In 5, the ligands bridge the nearly symmetrical Ag3 triangular core with short Ag-Ag separations of 2.7765(8), 2.7832(8), and 2.7598(8) A. All of these complexes, including the ligand precursor, are intensely luminescent in solution and the solid state.     

Short metal-metal separations in a highly luminescent trimetallic Ag(I) complex stabilized by bridging NHC ligands

Reaction of 1,3-bis(2-pyridinylmethyl)-1H-imidazolium salt, [H(pyCH(2))(2)im]X (X = BF(4)(-) or Cl(-)), with silver oxide in acetonitrile readily yields yellow-brown [((pyCH(2))(2)im)(2)Ag]X, 1.BF(4) or 1.Cl. The chloride salt crystallizes with 3.650 A intermolecular Ag...Ag interactions while 1.BF(4) shows no short intermolecular interaction. Addition of excess Ag(BF(4)) produces the homoleptic carbene bridged trimetallic species, [(mu-NHC)(3)Ag(3)](BF(4))(3), 2. This species contains very short Ag-Ag separations between 2.7249(10) and 2.7718(9) A. In solution, these complexes are photoluminescent.     

Aspects of column fabrication for packed capillary electrochromatography

Various parameters have been evaluated to develop a process for optimization of column manufacture for packed capillary electrochromatography (CEC). Spherisorb ODS-1 was packed into 75 microm I.D. capillaries to establish a standard set of packing conditions to afford high-performance columns free of voids. Numerous silica-based packing materials including porous and non-porous reversed-phase and ion-exchange phases were employed to evaluate the applicability of the standard conditions. Success of column manufacture and performance demonstrate a relationship to the colligative properties of the packing materials under the applied conditions. Frequently encountered difficulties arising from inadequate column conditioning and void formation in the packed bed are identified and discussed.     

Synthesis,Structure, Photophysical Properties,and Photostability of Benzodipyrenes

This work explores the syntheses, structures, photophysical properties, and photostability of benzodipyrenes (BDPs). BDPs were synthesized through an InCl₃-AgNTf₂-catalyzed, four-fold alkyne benzannulation reaction. The structures of BDP 4 a and its corresponding endoperoxide product were unambiguously confirmed by X-ray crystallography. The BDPs reported here can also be recognized as peri- and cata-benzannulated pentacenes with a non-functionalized central ring. Unlike the previous reported pentacene-based polycyclic aromatic hydrocarbons, the absorbances of the BDPs were blueshifted by ca. 40 nm relative to pentacene, even after extension of π-conjugation. The newly synthesized BDP products exhibit relatively good stability with half-lives as high as 4612 min in THF.     

Natural Products Extracted from Fungal Species as New Potential Anti-Cancer Drugs: A Structure-Based Drug Repurposing Approach Targeting HDAC7

Mushrooms can be considered a valuable source of natural bioactive compounds with potential polypharmacological effects due to their proven antimicrobial, antiviral, antitumor, and antioxidant activities. In order to identify new potential anticancer compounds, an in-house chemical database of molecules extracted from both edible and non-edible fungal species was employed in a virtual screening against the isoform 7 of the Histone deacetylase (HDAC). This target is known to be implicated in different cancer processes, and in particular in both breast and ovarian tumors. In this work, we proposed the ibotenic acid as lead compound for the development of novel HDAC7 inhibitors, due to its antiproliferative activity in human breast cancer cells (MCF-7). These promising results represent the starting point for the discovery and the optimization of new HDAC7 inhibitors and highlight the interesting opportunity to apply the “drug repositioning” paradigm also to natural compounds deriving from mushrooms.     

Stimulated emission of GaN under high one and two quantum excitation

Stimulated emission at 3.435 eV in GaN at 80 K is reported. This emission is attributed to a cooperative excitonic process and is observed only in undoped samples. One and two photon optical pumping has been used and optical gain of about 10³ cm^-1 has been measured.     

Synthesis and structural characterisation of CdS nanoparticles prepared in a four-components "water-in-oil" microemulsion

Nanostructured semiconductor particles are currently under intense investigation because of their enhanced photoreactivity and photocatalytic properties due to the quantum-size effect and the dependence of the photophysical and photochemical properties on their size as it approaches the exciton diameter. This increasing interest has led to the development of several synthetic procedures to prepare and stabilise uniform crystallites. In this paper, we report a novel synthetic pathway to obtain cadmium sulphide (CdS) nanoparticles in a quaternary "water-in-oil" microemulsion formed by a cationic surfactant cetyltrimethylammonium bromide (CTAB), pentanol, n-hexane and water. The synthesis of CdS in this system is achieved by mixing two microemulsions containing Cd(NO3)2 and Na2S, respectively. The nanocrystals have been characterised by using UV--visible spectroscopy and Transmission Electron Microscopy to investigate the influence of various parameters of the particles' formation and stability in solution. Capping of nanoparticles with suitable organic molecules has been performed in order to increase their stability and afford solubility in a wide range of solvents.