Nanomaterials based upon silylated layered double hydroxides

A class of nanomaterials based upon the surface modification of layered double hydroxides (LDHs) have been synthesized by grafting silanes onto the surfaces of the LDH. By in situ coprecipitation, the surfaces of a LDH have been modified through grafting of 3-aminopropyltriethoxysilane (APTS) using the anionic surfactant Na-dodecylsulfonate (SDS). The synthesized nanomaterials were characterized by X-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR FTIR), thermogravimetry (TG) and transmission electron microscopy (TEM). The grafted LDH (LDH-G) displays distinct XRD patterns proving the obtained materials are a new and different phase. The FTIR spectra of the silylated hydrotalcite show bands attributed to Si-O-M (M = Mg and Al) vibration at 996 cm⁻¹, suggesting that APTS has successfully been grafted onto the LDH layers. The TG curves prove the grafted sample has less M-OH concentration and less interlayer water molecules, as indicated by the M-OH consumption during the condensation reaction between Si-OH and M-OH on the LDH surface. The grafted sample displays a ribbon-like thin sheet in the TEM images, with the lateral thickness estimated as 2.5 nm.     

Raman spectroscopic study of the uranyl tellurite mineral moctezumite PbUO2(TeO3)2

The uranyl tellurite mineral moctezumite, Pb(UO₂)(TeO₃)₂, was studied by Raman spectroscopy and complemented with infrared spectroscopy. The presence of the stretching and bending vibrations of uranyl (UO₂)²⁺ and tellurite (TeO₃)²⁻ ions was inferred, and the observed bands were assigned to uranyl and tellurite units vibrations. U O bond lengths calculated from the spectra with two empirical relations are close to those inferred from the X‐ray single‐crystal structure of moctezumite. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the tellurite minerals: graemite CuTeO3·H2O and teineite CuTeO3·2H2O

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO₃), (b) A(XO₃)·xH₂O, (c) A₂(XO₃)₃·xH₂O, (d) A₂(X₂O₅) and (e) A(X₃O₈). Raman spectroscopy has been used to study the tellurite minerals teineite and graemite; both contain water as an essential element of their stability. The tellurite ion should show a maximum of six bands. The free tellurite ion will have C_3v symmetry and four modes, 2A₁ and 2 E. Raman bands for teineite at 739 and 778 cm⁻¹ and for graemite at 768 and 793 cm⁻¹ are assigned to the ν₁ (TeO₃)²⁻ symmetric stretching mode while bands at 667 and 701 cm⁻¹ for teineite and 676 and 708 cm⁻¹ for graemite are attributed to the ν₃ (TeO₃)²⁻ antisymmetric stretching mode. The intense Raman band at 509 cm⁻¹ for both teineite and graemite is assigned to the water librational mode. Raman bands for teineite at 318 and 347 cm⁻¹ are assigned to the (TeO₃)²⁻ν₂(A₁) bending mode and the two bands for teineite at 384 and 458 cm⁻¹ may be assigned to the (TeO₃)²⁻ν₄(E) bending mode. Prominent Raman bands, observed at 2286, 2854, 3040 and 3495 cm⁻¹, are attributed to OH stretching vibrations. The values for these OH stretching vibrations provide hydrogen bond distances of 2.550(6) Å (2341 cm⁻¹), 2.610(3) Å (2796 cm⁻¹) and 2.623(2) Å (2870 cm⁻¹) which are comparatively short for secondary minerals. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman and mid‐IR spectroscopic study of the magnesium carbonate minerals—brugnatellite and coalingite

Two hydrated hydroxy magnesium carbonate minerals brugnatellite and coalingite with a hydrotalcite‐like structure were studied by Raman spectroscopy. Intense bands are observed at 1094 cm⁻¹ for brugnatellite and at 1093 cm⁻¹ for coalingite attributed to the CO₃²⁻ν₁ symmetric stretching mode. Additional low intensity bands are observed at 1064 cm⁻¹. The existence of two symmetric stretching modes is accounted for in terms of different anion structural arrangements. Very low intensity bands at 1377 and 1451 cm⁻¹ are observed for brugnatellite, and the Raman spectrum of coalingite displays two bands at 1420 and 1465 cm⁻¹ attributed to the (CO₃)²⁻ν₃ antisymmetric stretching modes. Very low intensity bands at 792 cm⁻¹ for brugnatellite and 797 cm⁻¹ for coalingite are assigned to the CO₃²⁻ out‐of‐plane bend (ν₂). X‐ray diffraction studies by other researchers have shown that these minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality and explains why the Raman spectra of these minerals have not been previously or sufficiently described. A comparison is made with the Raman spectra of other hydrated magnesium carbonate minerals. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the metatellurate mineral: xocomecatlite Cu3TeO4(OH)4

The mineral xocomecatlite is a hydroxy metatellurate mineral with Te⁶⁺ O₄ units. Tellurates may be subdivided according to their formula into three types of tellurate minerals: type (a) (AB)_m (TeO₄)_pZ_q, type (b) (AB)_m(TeO₆)^·xH₂O and (c) compound tellurates in which a second anion including the tellurite anion, is involved. The mineral xocomecatlite is an example of the first type. Raman bands for xocomecatlite at 710, 763 and 796 cm⁻¹, and 600 and 680 cm⁻¹ are attributed to the ν₁(TeO₄)²⁻ symmetric and ν₃ antisymmetric stretching mode. Raman bands observed at 2867 and 2926 cm⁻¹ are assigned to TeOH stretching vibrations and enable estimation of the hydrogen bond distances of 2.622 Å (2867 cm⁻¹), 2.634 Å (2926 cm⁻¹) involving these OH units. The hydrogen bond distances are very short implying that they are necessary for the stability of the mineral. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and Raman spectroscopic study of Mg/Al,Fe hydrotalcites with variable cationic ratios

Hydrotalcites of formula Mg₆(Al,Fe)₂(OH)₁₆(CO₃)·4H₂O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d‐spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (1) brucite layer OH stretching vibrations, (2) water stretching bands and (3) water strongly hydrogen bonded to the carbonate anion. Multiple (CO₃)²⁻ symmetric stretching bands suggest that different types of (CO₃)²⁻ exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the two Raman bands at around 3600 cm⁻¹, attributed to Mg OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm⁻¹, indicating that water is strongly hydrogen bonded to both interlayer anions and the brucite‐like surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the mixed anion sulphate–arsenate mineral parnauite Cu9[(OH)10|SO4|(AsO4)2]·7H2O

The mixed anion mineral parnauite Cu₉[(OH)₁₀|SO₄|(AsO₄)₂]·7H₂O has been studied by Raman spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands are observed and are resolved into component bands. Two intense bands at 859 and 830 cm⁻¹ are assigned to the ν₁ (AsO₄)³⁻ symmetric stretching and ν₃ (AsO₄)³⁻ antisymmetric stretching modes. The comparatively sharp band at 976 cm⁻¹ is assigned to the ν₁ (SO₄)²⁻ symmetric stretching mode and a broad‐spectral profile centered upon 1097 cm⁻¹ is attributed to the ν₃ (SO₄)²⁻ antisymmetric stretching mode. A comparison of the Raman spectra is made with other arsenate‐bearing minerals such as carminite, clinotyrolite, kankite, tilasite and pharmacosiderite. Copyright © 2009 John Wiley & Sons, Ltd.     

Advances in Biomimetic Nanoparticles for Targeted Cancer Therapy and Diagnosis

Biomimetic nanoparticles have recently emerged as a novel drug delivery platform to improve drug biocompatibility and specificity at the desired disease site, especially the tumour microenvironment. Conventional nanoparticles often encounter rapid clearance by the immune system and have poor drug-targeting effects. The rapid development of nanotechnology provides an opportunity to integrate different types of biomaterials onto the surface of nanoparticles, which enables them to mimic the natural biological features and functions of the cells. This mimicry strategy favours the escape of biomimetic nanoparticles from clearance by the immune system and reduces potential toxic side effects. Despite the rapid development in this field, not much has progressed to the clinical stage. Thus, there is an urgent need to develop biomimetic-based nanomedicine to produce a highly specific and effective drug delivery system, especially for malignant tumours, which can be used for clinical purposes. Here, the recent developments for various types of biomimetic nanoparticles are discussed, along with their applications for cancer imaging and treatments.     

Search for solar hadronic axions produced by a bremsstrahlung-like process

We have searched for hadronic axions which may be produced in the Sun by a bremsstrahlung-like process, and observed in the HPGe detector by an axioelectric effect. A conservative upper limit on the hadronic axion mass of ma?334 eV$m_a?334\text{eV}$ at 95% C.L. is obtained. Our experimental approach is based on the axion–electron coupling and it does not include the axion–nucleon coupling, which suffers from the large uncertainties related to the estimation of the flavor-singlet axial-vector matrix element.     

Observation of enhanced orbital electron-capture nuclear decay rate in a compact medium

The eigenstate energies of an atom increase under spatial confinement and this effect should increase the electron density of the orbital electrons at the nucleus thus increasing the decay rate of an electron capturing radioactive nucleus. We have observed that the orbital electron capture rates of ¹⁰⁹In and ¹¹⁰Sn increased by (1.00±0.17)%$(1.00\pm 0.17)\mathrm{\%}$ and (0.48±0.25)%$(0.48\pm 0.25)\mathrm{\%}$ respectively when implanted in the smaller Au lattice compared to implantation in a larger Pb lattice. These observations are interpreted to be a result of the higher compression experienced by the large radioactive atoms in the smaller spatial confinement of the Au lattice.