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1.
PLoS One ; 15(2): e0227811, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32023266

RESUMO

Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to non-fluorinated neonicotinoids. Neonicotinoids containing trifluoroacethyl substituent reveal increased insecticidal activity due to higher hydrophobicity and metabolic stability. We synthesized novel neonicotinoid insecticides containing fluorinated acceptor groups and their interactions were estimated with the nicotinic acetylcholine receptor (nAChR) binding site by molecular docking studies, to evaluate their larvicidal activity against A. darlingi, and to assess their outdoor photodegradation behavior. New neonicotinoid analogues were prepared and characterized by NMR and mass-spectrometry. The synthesized molecules were modelled by time-dependent density functional theory and analyzed, their interaction with nAChR was investigated by molecular docking. Their insecticide activity was tested on Anopheles larvae collected in suburban area of Manaus, Brazil. Four new fluorinated neonicotinoid analogs were prepared and tested against 3rd instars larvae of A. darlingi showing high larvicidal activity. Docking studies reveal binding modes of the synthesized compounds and suggest that their insecticidal potency is governed by specific interactions with the receptor binding site and enhanced lipophilicity. 2-Chloro-5-(2-trifluoromethyl-pyrrolidin-1-ylmethyl)pyridine 5 showed fast degradation in water maintaining high larvicidal activity. All obtained substances possessed high larvicidal activity in low concentrations in 48 hours of exposure, compared to commercial flupyradifurone. Such activity is connected to a unique binding pattern of the synthesized compounds to insect's nAChR and to their enhanced bioavailability owing to introduction of fluorinated amino-moieties. Therefore, the compounds in question have a high potential for application as control agents for insects transmitting tropical diseases, and they will be less persistent in the environment.


Assuntos
Anopheles/efeitos dos fármacos , Halogenação , Inseticidas/toxicidade , Simulação de Acoplamento Molecular , Neonicotinoides/toxicidade , 4-Butirolactona/análogos & derivados , 4-Butirolactona/química , 4-Butirolactona/toxicidade , Animais , Inseticidas/química , Larva/efeitos dos fármacos , Neonicotinoides/síntese química , Neonicotinoides/química , Piridinas/química , Piridinas/toxicidade , Espectrofotometria Ultravioleta , Eletricidade Estática
2.
Nanotechnology ; 2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31978899

RESUMO

Amorphous SiO2-Nb2O5 nanolaminates and mixture films were grown by atomic layer deposition. The films were grown at 300 oC from Nb(OC2H5)5, Si2(NHC2H5)6, and O3 to thicknesses ranging from 13 to 130 nm. The niobium to silicon atomic ratio was varied in the range of 0.11-7.20. After optimizing the composition, resistive switching properties could be observed in the form of characteristic current-voltage behavior. Switching parameters in the conventional regime were well defined only in a SiO2:Nb2O5 mixture at certain, optimized, composition with Nb:Si atomic ratio of 0.13, whereas low-reading voltage measurements allowed recording memory effects in a wider composition range.

3.
ACS Omega ; 4(6): 11205-11214, 2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31460221

RESUMO

Herein, we report an atomic layer deposition (ALD) process for Cu2O thin films using copper(II) acetate [Cu(OAc)2] and water vapor as precursors. This precursor combination enables the deposition of phase-pure, polycrystalline, and impurity-free Cu2O thin films at temperatures of 180-220 °C. The deposition of Cu(I) oxide films from a Cu(II) precursor without the use of a reducing agent is explained by the thermally induced reduction of Cu(OAc)2 to the volatile copper(I) acetate, CuOAc. In addition to the optimization of ALD process parameters and characterization of film properties, we studied the Cu2O films in the fabrication of photoconductor devices. Our proof-of-concept devices show that approximately 20 nm thick Cu2O films can be used for photodetection in the visible wavelength range and that the thin film photoconductors exhibit improved device characteristics in comparison to bulk Cu2O crystals.

4.
Nanomaterials (Basel) ; 9(1)2019 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-30669454

RESUMO

Titanium dioxide nanotubes/hydroxyapatite nanocomposites were produced on a titanium alloy (Ti6Al4V/TNT/HA) and studied as a biocompatible coating for an implant surface modification. As a novel approach for this type of nanocomposite fabrication, the atomic layer deposition (ALD) method with an extremely low number of cycles was used to enrich titania nanotubes (TNT) with a very thin hydroxyapatite coating. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for determination of the structure and the surface morphology of the fabricated nanocoatings. The biointegration activity of the layers was estimated based on fibroblasts' proliferation on the TNT/HA surface. The antibacterial activity was determined by analyzing the ability of the layers to inhibit bacterial colonization and biofilm formation. Mechanical properties of the Ti6Al4V/TNT/HA samples were estimated by measuring the hardness, Young's module, and susceptibility to scratching. The results revealed that the nanoporous titanium alloy coatings enriched with a very thin hydroxyapatite layer may be a promising way to achieve the desired balance between biofunctional and biomechanical properties of modern implants.

5.
Angew Chem Int Ed Engl ; 57(44): 14538-14542, 2018 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-30048031

RESUMO

Rhenium is both a refractory metal and a noble metal that has attractive properties for various applications. Still, synthesis and applications of rhenium thin films have been limited. We introduce herein the growth of both rhenium metal and rhenium nitride thin films by the technologically important atomic layer deposition (ALD) method over a wide deposition temperature range using fast, simple, and robust surface reactions between rhenium pentachloride and ammonia. Films are grown and characterized for compositions, surface morphologies and roughnesses, crystallinities, and resistivities. Conductive rhenium subnitride films of tunable composition are obtained at deposition temperatures between 275 and 375 °C, whereas pure rhenium metal films grow at 400 °C and above. Even a just 3 nm thick rhenium film is continuous and has a low resistivity of about 90 µΩ cm showing potential for applications for which also other noble metals and refractory metals have been considered.

6.
Small ; 14(21): e1800547, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29673074

RESUMO

Semiconducting 2D materials, such as SnS2 , hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few-layer SnS2 films has remained a great challenge. Herein, continuous wafer-scale 2D SnS2 films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low-temperature (250 °C) postdeposition annealing. Uniform coating of large-area and 3D substrates is demonstrated owing to the unique self-limiting growth mechanism of atomic layer deposition. Detailed characterization confirms the 1T-type crystal structure and composition, smoothness, and continuity of the SnS2 films. A two-stage deposition process is also introduced to improve the texture of the films. Successful deposition of continuous, high-quality SnS2 films at low temperatures constitutes a crucial step toward various applications of 2D semiconductors.

7.
Adv Mater ; 30(24): e1703622, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29315833

RESUMO

2D materials research is advancing rapidly as various new "beyond graphene" materials are fabricated, their properties studied, and materials tested in various applications. Rhenium disulfide is one of the 2D transition metal dichalcogenides that has recently shown to possess extraordinary properties such as that it is not limited by the strict monolayer thickness requirements. The unique inherent decoupling of monolayers in ReS2 combined with a direct bandgap and highly anisotropic properties makes ReS2 one of the most interesting 2D materials for a plethora of applications. Here, a highly controllable and precise atomic layer deposition (ALD) technique is applied to deposit ReS2 thin films. Film growth is demonstrated on large area (5 cm × 5 cm) substrates at moderate deposition temperatures between 120 and 500 °C, and the films are extensively characterized using field emission scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray diffractometry using grazing incidence, atomic force microscopy, focused ion beam/transmission electron microscopy, X-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The developed ReS2 ALD process highlights the potential of the material for applications beyond planar structure architectures. The ALD process also offers a route to an upgrade to an industrial scale.

8.
Nanotechnology ; 29(5): 055301, 2018 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-29215346

RESUMO

We demonstrate the preparation and exploitation of multilayer metal oxide hard masks for lithography and 3D nanofabrication. Atomic layer deposition (ALD) and focused ion beam (FIB) technologies are applied for mask deposition and mask patterning, respectively. A combination of ALD and FIB was used and a patterning procedure was developed to avoid the ion beam defects commonly met when using FIB alone for microfabrication. ALD grown Al2O3/Ta2O5/Al2O3 thin film stacks were FIB milled with 30 keV gallium ions and chemically etched in 5% tetramethylammonium hydroxide at 50 °C. With metal evaporation, multilayers consisting of amorphous oxides Al2O3 and Ta2O5 can be tailored for use in 2D lift-off processing, in preparation of embedded sub-100 nm metal lines and for multilevel electrical contacts. Good pattern transfer was achieved by lift-off process from the 2D hard mask for micro- and nano-scaled fabrication. As a demonstration of the applicability of this method to 3D structures, self-supporting 3D Ta2O5 masks were made from a film stack on gold particles. Finally, thin film resistors were fabricated by utilizing controlled stiction of suspended Ta2O5 structures.

9.
Nanomaterials (Basel) ; 7(7)2017 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-28737725

RESUMO

Plasma enhanced atomic layer deposition (PEALD) of silver nanoparticles on the surface of 1-D titania coatings, such as nanotubes (TNT) and nanoneedles (TNN), has been carried out. The formation of TNT and TNN layers enriched with dispersed silver particles of strictly defined sizes and the estimation of their bioactivity was the aim of our investigations. The structure and the morphology of produced materials were determined using X-ray photoelectron spectroscopy (XPS) and scanning electron miscroscopy (SEM). Their bioactivity and potential usefulness in the modification of implants surface have been estimated on the basis of the fibroblasts adhesion and proliferation assays, and on the basis of the determination of their antibacterial activity. The cumulative silver release profiles have been checked with the use of inductively coupled plasma-mass spectrometry (ICPMS), in order to exclude potential cytotoxicity of silver decorated systems. Among the studied nanocomposite samples, TNT coatings, prepared at 3, 10, 12 V and enriched with silver nanoparticles produced during 25 cycles of PEALD, revealed suitable biointegration properties and may actively counteract the formation of bacterial biofilm.

10.
Int J Pharm ; 525(1): 160-174, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28432020

RESUMO

Active pharmaceutical ingredients (APIs) are predominantly organic solid powders. Due to their bulk properties many APIs require processing to improve pharmaceutical formulation and manufacturing in the preparation for various drug dosage forms. Improved powder flow and protection of the APIs are often anticipated characteristics in pharmaceutical manufacturing. In this work, we have modified acetaminophen particles with atomic layer deposition (ALD) by conformal nanometer scale coatings in a one-step coating process. According to the results, ALD, utilizing common chemistries for Al2O3, TiO2 and ZnO, is shown to be a promising coating method for solid pharmaceutical powders. Acetaminophen does not undergo degradation during the ALD coating process and maintains its stable polymorphic structure. Acetaminophen with nanometer scale ALD coatings shows slowed drug release. ALD TiO2 coated acetaminophen particles show cytocompatibility whereas those coated with thicker ZnO coatings exhibit the most cytotoxicity among the ALD materials under study when assessed in vitro by their effect on intestinal Caco-2 cells.


Assuntos
Acetaminofen/química , Excipientes/química , Nanotecnologia , Células CACO-2 , Humanos , Pós , Propriedades de Superfície
11.
Int J Nanomedicine ; 11: 6771-6780, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-28008252

RESUMO

BACKGROUND: Coordination compounds of pentavalent antimony have been, and remain, the first-line drugs in leishmaniasis treatment for >70 years. Molecular forms of Sb (V) complexes are commercialized as sodium stibogluconate (Pentostam®) and meglumine antimoniate (MA) (Glucantime®). Ever-increasing drug resistance in the parasites limits the use of antimonials, due to the low drug concentrations being administered against high parasitic counts. Sb5+ toxicity provokes severe side effects during treatment. To enhance therapeutic potency and to increase Sb (V) concentration within the target cells, we decided to try a new active substance form, a hydrosol of Sb2O5·nH2O nanoparticles (NPs), instead of molecular drugs. METHODOLOGY/PRINCIPAL FINDINGS: Sb2O5·nH2O NPs were synthesized by controlled SbCl5 hydrolysis in a great excess of water. Sb2O5·nH2O phase formation was confirmed by X-ray diffraction. The surface of Sb (V) NPs was treated with ligands with a high affinity for target cell membrane receptors. The mean particle size determined by dynamic light scattering and transmission electron microscopy was ~35-45 nm. In vitro tests demonstrated a 2.5-3 times higher antiparasitic activity of Sb (V) nanohybrid hydrosols, when compared to MA solution. A similar comparison for in vivo treatment of experimental cutaneous leishmaniasis with Sb5+ nanohybrids showed a 1.75-1.85 times more effective decrease in the lesions. Microimages of tissue fragments confirmed the presence of NPs inside the cytoplasm of infected macrophages. CONCLUSION/SIGNIFICANCE: Sb2O5·nH2O hydrosols are proposed as a new form of treatment for cutaneous leishmaniasis caused by Leishmania amazonensis. The NPs penetrate directly into the affected cells, creating a high local concentration of the drug, a precondition to overcoming the parasite resistance to molecular forms of pentavalent antimonials. The nanohybrids are more effective at a lower dose, when compared to MA, the molecular drug. Our data suggest that the new form of treatment has the potential to reduce and simplify the course of cutaneous leishmaniasis treatment. At the same time, Sb2O5·nH2O hydrosols provide an opportunity to avoid toxic antimony (V) spreading throughout the body.


Assuntos
Antimônio/farmacologia , Antiprotozoários/química , Antiprotozoários/farmacologia , Nanopartículas/química , Óxidos/farmacologia , Animais , Antimônio/química , Avaliação Pré-Clínica de Medicamentos/métodos , Difusão Dinâmica da Luz , Leishmania mexicana/efeitos dos fármacos , Leishmania mexicana/patogenicidade , Leishmaniose Cutânea/tratamento farmacológico , Masculino , Mesocricetus , Microscopia Eletrônica de Transmissão , Óxidos/química , Tamanho da Partícula , Difração de Raios X
12.
Langmuir ; 32(41): 10559-10569, 2016 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-27673703

RESUMO

Nucleation and conformality are important issues, when depositing thin films for demanding applications. In this study, iridium and iridium dioxide (IrO2) films were deposited by atomic layer deposition (ALD), using five different processes. Different reactants, namely, O2, air, consecutive O2 and H2 (O2 + H2), and consecutive O3 and H2 (O3 + H2) pulses were used with iridium acetylacetonate [Ir(acac)3] to deposit Ir, while IrO2 was deposited using Ir(acac)3 and O3. Nucleation was studied using a combination of methods for film thickness and morphology evaluation. In conformality studies, microscopic lateral high-aspect-ratio (LHAR) test structures, specifically designed for accurate and versatile conformality testing of ALD films, were used. The order of nucleation, from the fastest to the slowest, was O2 + H2 > air ≈ O2 > O3 > O3 + H2, whereas the order of conformality, from the best to the worst, was O3 + H2 > O2 + H2 > O2 > O3. In the O3 process, a change in film composition from IrO2 to metallic Ir was seen inside the LHAR structures. Compared to the previous reports on ALD of platinum-group metals, most of the studied processes showed good to excellent results.

13.
ACS Omega ; 1(6): 1296-1306, 2016 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-31457197

RESUMO

Hybrid halide perovskite thin films are applicable in a wide range of devices such as light-emitting diodes, solar cells, and photodetectors. The optoelectronic properties of perovskites together with their simple and inexpensive film deposition methods make these materials a viable alternative to established materials in these devices. However, the potential of perovskite materials is compromised by the limitations of the existing deposition methods, which suffer from trade-off among suitability for large-scale industrial production in a batch or roll-to-roll manner, deposition area, film quality, and costs. We addressed these limitations by developing a deposition method that is inexpensive, applicable to large substrate areas, scalable, and yields high-quality perovskite films. In this study, the low-cost electrodeposition (ED) method and sequential exposure to reagent vapors produce CH3NH3PbI3 perovskite films with thickness nonuniformity below 9% on a centimeter scale. PbO2 films are electrodeposited first and then undergo two vapor conversion steps, with HI vapor in the first step and CH3NH3I vapor in the second step. The second step yields CH3NH3PbI3 films that are continuous and consist of micrometer-sized grains. This process allows the preparation of both α- and ß-phase CH3NH3PbI3 films, offers a simple means to control the film thickness, and works over a wide range of film thicknesses. In this work, films with thicknesses ranging from 100 nm to 10 µm were prepared. ED and vapor conversion are inherently scalable techniques and hence the process described herein could benefit application areas in which large device areas and throughput are required, such as the production of solar cells.

14.
Angew Chem Int Ed Engl ; 54(48): 14321-5, 2015 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-26437764

RESUMO

The addition of Barton's base has a dramatic effect on the classic rhodium(III)-mediated hydrogenations promoted by Wilkinson's catalyst. Following the initial oxidative addition, a barrierless reductive elimination of HCl from the traditional rhodium(III) intermediates instantly produces a rhodium(I) monohydride species, which is remarkably reactive in the hydrogenation of several internal alkynes and functionalized trisubstituted alkenes. The direct formation of this species is unprecedented upon addition of molecular hydrogen and its catalytic potential has been hitherto barely explored.

15.
Nanotechnology ; 26(26): 265304, 2015 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-26062985

RESUMO

A focused ion beam (FIB) is otherwise an efficient tool for nanofabrication of silicon structures but it suffers from the poor thermal stability of the milled surfaces caused by segregation of implanted gallium leading to severe surface roughening upon already slight annealing. In this paper we show that selective etching with KOH:H2O2 solutions removes the surface layer with high gallium concentration while blocking etching of the surrounding silicon and silicon below the implanted region. This remedies many of the issues associated with gallium FIB nanofabrication of silicon. After the gallium removal sub-nm surface roughness is retained even during annealing. As the etching step is self-limited to a depth of 25-30 nm for 30 keV ions, it is well suited for defining nanoscale features. In what is essentially a reversal of gallium resistless lithography, local implanted areas can be prepared and then subsequently etched away. Nanopore arrays and sub-100 nm trenches can be prepared this way. When protective oxide masks such as Al2O3 grown with atomic layer deposition are used together with FIB milling and KOH:H2O2 etching, ion-induced amorphization can be confined to sidewalls of milled trenches.

16.
Nanotechnology ; 26(13): 134004, 2015 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-25764569

RESUMO

In this work we report on the influence of nitrogen ambient thermal effects on the performance of Pt/Al2O3/Si3N4/SiO2/Si memory capacitors. Two post deposition annealing (PDA) furnace steps were employed, at 850 and 1050 °C both for 15 min. The alumina films were deposited by atomic layer deposition using TMA/H2O at 250 °C. The structural characteristics of the stacks were evaluated by transmission electron microscopy and x-ray reflectivity measurements. The memory performance of the stacks was evaluated by write/erase and erase/write measurements, endurance and retention testing. It was found that in as-deposited state the Al2O3 layer is defective resulting in strong leakage currents, controlled by deep defects states. Thus, this behavior inhibits the memory functionality of the stacks. PDA crystallizes and condenses the Al2O3 transforming the layer from amorphous to polycrystalline. During this transformation the Al2O3 electrical quality improves greatly indicating that a significant number of these deep defects have been removed during annealing. Physical reasoning implies that the most plausible origin of these deep defects is hydrogen. However, the polycrystalline Al2O3 films showed inferior retention characteristics which are attributed to grain boundary related shallow defects. The findings of this work could pave the way for more efficient annealing schemes, in which an important factor is the time interval for hydrogen out-diffusion from the Al2O3 layer.

17.
J Am Chem Soc ; 137(12): 4038-41, 2015 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-25636083

RESUMO

We report the synthesis and reactivity of a chiral aminoborane displaying both rapid and reversible H2 activation. The catalyst shows exceptional reactivity in asymmetric hydrogenation of enamines and unhindered imines with stereoselectivities of up to 99% ee. DFT analysis of the reaction mechanism pointed to the importance of both repulsive steric and stabilizing intermolecular non-covalent forces in the stereodetermining hydride transfer step of the catalytic cycle.

18.
Angew Chem Int Ed Engl ; 54(6): 1749-53, 2015 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-25521538

RESUMO

Ansa-aminoborane 1 (ortho-TMP-C6H4-BH2; TMP = 2,2,6,6-tetramethylpiperid-1-yl), a frustrated Lewis pair with the smallest possible Lewis acidic boryl site (-BH2), is prepared. Although it is present in quenched forms in solution, and BH2 represents an acidic site with reduced hydride affinity, 1 reacts with H2 under mild conditions producing ansa-ammonium trihydroborate 2. The thermodynamic and kinetic features as well as the mechanism of this reaction are studied by variable-temperature NMR spectroscopy, spin-saturation transfer experiments, and DFT calculations, which provide comprehensive insight into the nature of 1.

19.
J Phys Chem A ; 119(11): 2298-306, 2015 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-25105932

RESUMO

Bi2Te3 thin films were deposited by atomic layer deposition (ALD) from BiCl3 and (Et3Si)2Te at 160-300 °C. The process was studied in detail, and growth properties typical of ALD were verified. Films were stoichiometric with low impurity content. The film thickness was easily controlled with the number of deposition cycles. Properties of the ALD Bi2Te3 thin films were found to be comparable to those reported in literature for Bi2Te3 films made by other methods. Films crystallized to a rhombohedral phase, and there was a preferred orientation to the growth. Electrical and thermoelectric properties were also determined to be comparable to literature values.

20.
Biointerphases ; 9(3): 031008, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25280849

RESUMO

Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts.


Assuntos
Carbonato de Cálcio/química , Durapatita/química , Nanopartículas/química , Humanos , Fosfatos/química , Solubilidade , Difração de Raios X
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