Chemical vapor deposition and characterization of nitrogen doped TiO2 thin films on glass substrates

Photocatalytically active, N-doped TiO2 thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH3 as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R=[NH3]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R=2200, the N-doped TiO2 layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375–400 °C). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO2 films of comparable thickness

Chemical vapor infiltration of photocatalytically active TiO2 thin films on glass microfibers

Due to the high diffusivity of the chemical species, chemical vapor infiltration (CVI) is a suitable process for the conformal coverage of objects with large dimensions and complex shape geometry. Its large scale capacity and high reproducibility have made the technique favorable for the deposition of non-oxide ceramics. There are few works on other materials and metal-organic compounds are rarely used as molecular precursors. In this study we focus on the deposition of anatase thin films on substrates with large surface area (microfibers) for photocatalytic air treatment systems. Titanium tetra-isopropoxide (TTIP) was used as precursor without additional oxygen source. Using low mole fractions (26–124×10−5) and low deposition temperatures (300–400 °C), a relatively good thickness uniformity was obtained along the reactor axis. Infiltration experiments were achieved in this temperature range and under 1 Torr for high TTIP diffusivity (110–146 cm2 s−1) and low initial Thiele modulus (0.11–0.13) values. Photocatalytic activity of TiO2 coated glass microfiber samples depends on the film morphology, average thickness and infiltration efficiency. It is shown that this later parameter plays a major role due to the increase of active surface area

Oxygen vacancies in strained SrTiO3_{3} thin films: formation enthalpy and manipulation

We report the enthalpy of oxygen vacancy formation in thin films of electron-doped SrTiO$_{3}$, under different degrees of epitaxial stress. We demonstrate that both compressive and tensile strain decrease this energy at a very similar rate, and promote the formation of stable doubly ionized oxygen vacancies. Moreover, we also show that unintentional cationic vacancies introduced under typical growth conditions, produce a characteristic rotation pattern of TiO$_6$ octahedra. The local concentration of oxygen vacancies can be modulated by an electric field with an AFM tip, changing not only the local electrical potential, but also producing a non-volatile mechanical response whose sign (up/down) can be reversed by the electric field.Comment: Physical Review B (accepted for publication

Advances in the therapy of cancer pain: from novel experimental models to evidence-based treatments

Cancer related pain may be due to the malignant disease itself, or subsequent to treatments, such as surgery, chemotherapy or radiation therapy. The pathophysiology of pain due to cancer may be complex and include a variety of nociceptive, inflammatory, and neuropathic mechanisms. Despite modern advances in pharmacotherapy, cancer pain remains overall under-treated in a world-wide scale, and a main reason is lack of understanding of its pertinent pathophysiology and basic pharmacology. Recently, pertinent animal models have facilitated understanding of the pathobiology and have advanced the pharmacology of cancer pain, with significant translational applicability to clinical practice. Furthermore, quantitative and qualitative systematic reviews, integrating the best available evidence, indicate the validity of treatments that fit into an expanded view of the WHO-analgesic ladder. Appropriate current treatments include a valid therapeutic role of non-opioid and opioid analgesics, adjuvants -such as gabapentin, biphosphonates, palliative radiation therapy and radiopharmaceutical compounds, and interventional pain therapy (including neuraxial drug infusion and verterbroplasty for spine metastases) in selected patients. Overall, experimental animal models simulating cancer pain have been useful in providing pertinent information on the pathophysiology of cancer pain, and provide a testing ground for established and novel therapies, which are validated by clinical evidence. This is clinically significant, considering the epidemiological dimensions and the problematic nature of cancer pain

Thiotepa hyperpigmentation preceding epidermal necrosis: malignant intertrigo misdiagnosed as Stevens-Johnson syndrome-toxic epidermal necrolysis overlap

Thiotepa is a common alkylating agent known to precipitate cutaneous reactions consistent with toxic erythema of chemotherapy, including erythema and hyperpigmentation. Herein, we describe an atypical case of malignant intertrigo involving preferential erythema and desquamation not only of skin folds but also of occluded areas after thiotepa-based conditioning. The diagnosis was complicated by concurrent stomatitis and oral petechiae in the setting of autologous stem cell transplant 11 days prior for diffuse large B-cell lymphoma. Histopathological examination from two cutaneous sites demonstrated epidermal dysmaturation and eccrine gland necrosis consistent with thiotepa-induced desquamation and not Stevens-Johnson syndrome or graft-versus-host-disease. Malignant intertrigo can present with extensive cutaneous involvement, as evidenced by our patient who had 25% body surface area affected. Mucosal involvement is common with most chemotherapeutic regimens and its presence should not deter the astute clinician from consideration of a diagnosis of toxic erythema of chemotherapy. No further interventions were needed and the patient healed spontaneously

Microfibrous TiO2 supported photocatalysts prepared by metal-organic chemical vapor infiltration for indoor air and waste water purification

The photocatalytic degradation of gaseous (toluene) and aqueous (imazapyr, malic acid, orange G) pollutants over TiO2 supported photocatalysts is investigated using a batch reactor. A strong influence of the microstructural characteristics of TiO2 on the decomposition kinetics of the pollutants is found. Well crystallized, porous TiO2-anatase films grown under low pressure at 400–500 8C by MOCVD on glass plates and by MOCVI on glass micro-fibers are the best heterogeneous photocatalysts, showing the highest activity. We demonstrate a good control of these characteristics by choosing the deposition parameters. Achieving conformal coverage (i.e. good infiltration) of glass micro-fibers by the TiO2 thin films has also a strong influence on the photocatalytic activity. A correlation between optimal infiltration, film microstructure and photocatalytic activity is established. Strong similarities between optimal photocatalytic decomposition rate in gas and liquid phase were found with respect to the film microstructure and the photocatalyst mass. The total mineralization of the toluene was prevented because of the deactivation of the photocatalyst surface. However the reactivation of the photocatalyst was achieved by UV irradiation under oxygen stream. This allows a long-term use of the photocatalyst