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1.
Cancer Med ; 12(14): 15612-15627, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37317676

RESUMO

BACKGROUND: Patients' lack of knowledge about their own disease may function as a barrier to shared decision-making and well-being. This study aimed to evaluate the impact of written educational materials on breast cancer patients. METHODS: This multicenter, parallel, unblinded, randomized trial included Latin American women aged ≥18 years with a recent breast cancer diagnosis yet to start systemic therapy. Participants underwent randomization in a 1:1 ratio to receive a customizable or standard educational brochure. The primary objective was accurate identification of molecular subtype. Secondary objectives included identification of clinical stage, treatment options, participation in decision-making, perceived quality of information received, and illness uncertainty. Follow-up occurred at 7-21 and 30-51 days post-randomization. CLINICALTRIALS: gov identifier: NCT05798312. RESULTS: One hundred sixty-five breast cancer patients with a median age of 53 years and 61 days from diagnosis were included (customizable: 82; standard: 83). At first available assessment, 52%, 48%, and 30% identified their molecular subtype, disease stage, and guideline-endorsed systemic treatment strategy, respectively. Accurate molecular subtype and stage identification were similar between groups. Per multivariate analysis, customizable brochure recipients were more likely to identify their guideline-recommended treatment modalities (OR: 4.20,p = 0.001). There were no differences between groups in the perceived quality of information received or illness uncertainty. Customizable brochure recipients reported increased participation in decision-making (p = 0.042). CONCLUSIONS: Over one third of recently diagnosed breast cancer patients are incognizant of their disease characteristics and treatment options. This study demonstrates a need to improve patient education and shows that customizable educational materials increase patients' understanding of recommended systemic therapies according to individual breast cancer characteristics.


Assuntos
Neoplasias da Mama , Humanos , Feminino , Adolescente , Adulto , Pessoa de Meia-Idade , Neoplasias da Mama/diagnóstico , Neoplasias da Mama/terapia , Folhetos , Tomada de Decisão Compartilhada
2.
Healthcare (Basel) ; 12(1)2023 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-38200967

RESUMO

This article presents an exploration of conversational chatbots designed to alleviate loneliness among older adults. In addition to technical evaluation, it delves into effective communication between these systems and this demographic group, considering linguistic nuances, communicative preferences, and specific emotional needs. The intrinsic importance of chatbots as innovative solutions in combating loneliness is highlighted, emphasizing their ability to be understanding and empathetic allies, contributing to emotional well-being and socialization. The article explores how improved emotional well-being can positively impact the health and quality of life of older adults. The methodology, rooted in triangulation between a literature review and qualitative research through interviews and focus groups with older adults, provides a comprehensive insight into the findings. Ethical, technical, and design considerations such as privacy, autonomy, technology adaptation, and usability are also addressed. The article concludes with practical recommendations for developing user-friendly interfaces that encourage the active participation of older adults in chatbots. This holistic approach not only analyzes the technical effectiveness of chatbots in mitigating loneliness in older adults but delves into human, ethical, and practical aspects, enriching the understanding and implementation of these agents for social and emotional support.

3.
Boca Raton; CRC Press; 1; 2021. [19] p. tab, ilus.
Monografia em Inglês | LILACS, BVSDIP | ID: biblio-1566172

RESUMO

The adoption of novel integrated vector management (IVM) strategies requires proof-of-concept demonstrations. To implement a community-based intervention, for the control of vectors of Chagas disease in Guatemala, we engaged all relevant stakeholder groups. Based on this and previous experiences of the authors on engaged research and community-based interventions, several key factors can help facilitate effective integration of stakeholders in support of area-wide integrated vector management (AW - IVM) programmes. First and foremost, the diversity of stakeholders needs to be engaged early-on in the participatory action research and implementation processes, to provide ownership and contribute ideas on how to design and implement an intervention. Another important component, situational analysis regarding current pest control policies, practices and relevant stakeholders, is generated through interviews with key informants, at both national and local levels (governmental and non-governmental organizations); it can facilitate the joint identification of strengths, weaknesses, opportunities and threats regarding current pest control strategies and proposing solutions through an AW-IVM approach. In addition, successful AW - IVM can result from identifying locally relevant strategies to implement the proof-of-concept demonstrative project. Further, it is critical to maintain constant communication with the local and national leaders, involving them throughout the implementation and evaluation processes. Flexibility should also be built into the project to allow for community-driven changes in the strategy, through a cyclical joint reflective process. Periodic feedback of project development needs to be scheduled with key stakeholders to maintain rapport. Finally, the results of the evaluation should be shared and discussed with stakeholders to ensure long-term sustainability of the programme, intervention, or project. Here we present the citizen engagement procedures used to integrate community members, health officials, and non-governmental organization staff for Chagas disease control in a region of Guatemala. We demonstrate how these methods can be applied to support AW-IVM programmes, so that communities and authorities are actively involved in the development and implementation of a jointly agreed intervention. In 2012, we developed the IVM intervention in an area of Guatemala with persistentTriatoma dimidiata (Latreille) infestation that is associated with the presence of infected rodents (rats and mice), that act as reservoirs of the Trypanosoma cruzi Chagas parasites inside the households. Nine control communities received only the Ministry of Health insecticide application against the vector and nine intervention communities participated in the AW-IVM intervention. The intervention included a programme for rodent control by the community members, together with education about the risk factors for vector infestation, and insecticide application by the Ministry of Health. Entomological evaluations in 2014 and 2015 showed that vector infestation remained significantly lower in both intervention and control communities. In 2015, we found that there was a higher acceptance of vector surveillance activities in the intervention communities compared to control communities, suggesting that participatory activities increase programme sustainability. Finally, we found that there was a significant increase over time in the number of households with infected vectors in the control group, whereas there was no significant increase in the communities that participated in the programme. Thus, an AW-IVM programme including simultaneous rodent and vector control could reduce the risk of Chagas infection in communities with persistent vector infestation.


Assuntos
Rhodnius , Triatoma , Trypanosoma , América Central , Doença de Chagas , Participação Social , Inseticidas
4.
Oncologist ; 25(12): 1047-1054, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33400352

RESUMO

INTRODUCTION: In Mexico, there are considerable health system delays in the diagnosis and treatment initiation of women with breast cancer. Alerta Rosa is a navigation program in Nuevo Leon that aims to reduce barriers that impede the timely management of these patients. PATIENTS AND METHODS: Since December 2017, women who registered to receive medical evaluations by Alerta Rosa were stratified based on their clinical characteristics into three priority groups ("Red," "Yellow," and "Green"). According to the category assigned, patients were scheduled imaging studies and medical appointments with breast specialists on a preferential basis. RESULTS: Up until December 2019, 561 patients were scheduled for medical evaluations. Of them, 59% were classified as "Red," 25% "Yellow," and 16% "Green" priority. The median time from stratification to first medical evaluation was 4, 6, and 7 days, respectively (p = .003). Excluding those who had a prior breast cancer diagnosis, 21 patients were diagnosed by Alerta Rosa, with the initial "Red" priority classification demonstrating a sensitivity of 95% (95% confidence interval [CI], 75.1%-99.9%) and specificity of 42% (95% CI, 37.1%-47.1%) for breast cancer. The median time elapsed from initial patient contact to diagnosis and treatment initiation was 16 days and 39 days, respectively. The majority (72%) of patients were diagnosed at an early stage (0-II). CONCLUSION: This patient prioritization system adequately identified women with different probabilities of having breast cancer. Efforts to replicate similar triage systems in resource-constrained settings where screening programs are ineffective could prove to be beneficial in reducing diagnostic intervals and achieving early-stage diagnoses. IMPLICATIONS FOR PRACTICE: Low- and middle-income countries such as Mexico currently lack the infrastructure to achieve effective breast cancer screening and guarantee prompt access to health care when required. To reduce the disease burden in such settings, strategies targeting early detection are urgently needed. Patient navigation programs aid in the reduction of health system intervals and optimize the use of available resources. This article presents the introduction of a triage system based on initial patient concern. Appointment prioritization proved to be successful at reducing health system intervals and achieving early-stage diagnoses by overcoming barriers that impede early access to quality medical care.


Assuntos
Neoplasias da Mama , Navegação de Pacientes , Rosa , Neoplasias da Mama/diagnóstico , Diagnóstico Tardio , Detecção Precoce de Câncer , Feminino , Humanos , México
5.
Nanomaterials (Basel) ; 8(10)2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30309047

RESUMO

Nanofluids are systems with several interesting heat transfer applications, but it can be a challenge to obtain highly stable suspensions. One way to overcome this challenge is to create the appropriate conditions to disperse the nanomaterial in the fluid. However, when the heat transfer fluid used is a non-polar organic oil, there are complications due to the low polarity of this solvent. Therefore, this study introduces a method to synthesize TiO2 nanoparticles inside a non-polar fluid typically used in heat transfer applications. Nanoparticles produced were characterized for their structural and chemical properties using techniques such as X-ray Diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The nanofluid showed a high stability, which was analyzed by means of UV-vis spectroscopy and by measuring its particle size and ζ potential. So, this nanofluid will have many possible applications. In this work, the use as heat transfer fluid was tested. In this sense, nanofluid also presented enhanced isobaric specific heat and thermal conductivity values with regard to the base fluid, which led to the heat transfer coefficient increasing by 14.4%. Thus, the nanofluid prepared could be a promising alternative to typical HTFs thanks to its improved thermal properties and high stability resulting from the synthesis procedure.

6.
Oncologist ; 23(12): 1461-1466, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30126860

RESUMO

BACKGROUND: In Mexico, the median time between breast cancer (BC) symptom detection and treatment initiation is approximately 7 months. Alerta Rosa is a program that was developed with the intent of breaking down medical care barriers and reduce delays. PATIENTS AND METHODS: Through several media campaigns, we reached out to patients with breast symptoms or abnormal imaging studies. Patients contacted our call center or Facebook page. A navigator recorded their main complaint and scheduled a medical consultation with a specialist. We prioritized patients according to clinical risk. Those diagnosed with BC were referred to their health affiliation unit for care. RESULTS: To date, 656 patients have contacted our program. Median age was 44 years (range, 7-82). Patients reported becoming aware of Alerta Rosa mainly by word of mouth and TV. A total of 446 medical consultations were scheduled, and 309 patients attended their appointments. A biopsy procedure was solicited for 39 patients, and 22 were diagnosed with BC. Most patients had stage II (45%) or stage III (32%) disease. The median time from alert activation to treatment initiation was 33 days (range, 19-56) and from first medical evaluation to treatment initiation was 28 days (range, 16-48). CONCLUSION: In low- or middle-income countries, where BC screening programs do not effectively reach the target population, it is crucial to focus efforts in identifying and prioritizing symptomatic patients or those with abnormal imaging studies to ultimately downstage BC. Alerta Rosa proved to be successful in reducing health system intervals and could be replicated and adapted for other limited resource settings. IMPLICATIONS FOR PRACTICE: In countries such as Mexico, infrastructure and financial drawbacks limit the implementation of effective screening mammography programs. This article presents a novel and effective alternative to optimize resources and reduce health system intervals, so that patients in limited-resource settings can have access to prompt quality care. This strategy for early breast cancer detection focused efforts in prioritizing symptomatic women and those with abnormal breast imaging studies. This article presents novel information that will be useful for the development of effective early breast cancer detection with a focus on opportunistic rather than population-screening mammography in low-resource settings.


Assuntos
Neoplasias da Mama/epidemiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/patologia , Criança , Estudos de Coortes , Feminino , Humanos , México , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto Jovem
7.
Chemphyschem ; 18(4): 346-356, 2017 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-27958673

RESUMO

This study shows an analysis of the stability of nanofluids based on a eutectic mixture of diphenyl oxide and biphenyl, which is used as a heat transfer fluid (HTF) in concentrating solar energy, and NiO nanoparticles. Two surfactants are used to analyse the stability of the nanofluids: benzalkonium chloride (BAC) and 1-octadecanethiol (ODT). From an experimental perspective, the stability is analysed by means of UV/Vis spectroscopy, particle size measurements through the dynamic light-scattering technique, and ζ-potential measurements. The results show that the stability of the nanofluids improves with the use of BAC. DFT calculations are performed to understand the role played by the surfactants. The interaction of the surfactants with both the fluid and the NiO (100) surface is studied. Quantum theory of atoms in molecules (QTAIM) analysis shows that hydrogen bridge interactions favour the stability of the fluid-surfactant mixture. The more stabilising NiO-surfactant interaction involves the Ni-H interaction of the -SH and -CH3 groups of ODT and BAC. Also, nanofluids with BAC are favoured over those with ODT, which is in agreement with experimental results. The structural and electronic effects of incorporating the surfactant onto the NiO (100) surface are shown by using electron localisation function analysis, the non-covalent interaction index and projected density of states.

8.
Cir Cir ; 85(4): 312-319, 2017.
Artigo em Espanhol | MEDLINE | ID: mdl-27955847

RESUMO

BACKGROUND: Intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery facilitates the identification of anatomical structures in cervical endocrine surgery reducing the frequency of vocal cord paralysis. OBJECTIVE: To study the normal electrophysiological values of the vague and recurrent laryngeal nerves before and after thyroid surgery. To compare rates of injury of recurrent nerve before and after the introduction of the intraoperative neuromonitoring in thyroid surgery. MATERIAL AND METHODS: An observational, descriptive and prospective study in which a total of 490 patients were included. Between 2003-2010, surgery was performed on 411 patients (703 nerves at risk) with systematic identification of recurrent laryngeal nerves. Between 2010-2011 neuromonitorization was also systematically performed on 79 patients. RESULTS: Before the introduction of intraoperative neuromonitoring of 704 nerves at risk, there were 14 recurrent laryngeal nerve injuries. Since 2010, after the introduction of the intraoperative neuromonitoring in thyroid surgery, there has been no nerve injury in 135 nerves at risk. CONCLUSIONS: We consider the systematic identification of the recurrent laryngeal nerve is the 'gold standard' in thyroid surgery and the intraoperative neuromonitoring of nerves can never replace surgery but can complement it.


Assuntos
Complicações Intraoperatórias/prevenção & controle , Monitorização Neurofisiológica Intraoperatória , Traumatismos do Nervo Laríngeo Recorrente/prevenção & controle , Nervo Laríngeo Recorrente/fisiologia , Tireoidectomia , Nervo Vago/fisiologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Traumatismos do Nervo Laríngeo Recorrente/epidemiologia
9.
Water Sci Technol ; 2017(1): 184-193, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29698233

RESUMO

Photodegradation processes are of great interest in a range of applications, one of which is the photodecomposition of pollutants. For this reason, analysing nanoparticles that improve the efficiency of these processes under solar radiation are very necessary. Thus, in this study, TiO2 was doped with Mo and Cu using low-temperature hydrolysis as the method of synthesis. Pure TiO2 and x%MoS2/Cu/TiO2 nanoparticles were prepared, where x is the theoretical quantity of MoS2 added (0.0%, 1.0%, 5.5%, 10.0%), setting the nominal quantity of Cu at 0.5 wt.%. The samples obtained were characterized by X-ray diffraction, Raman spectroscopy, X-ray electron spectroscopy and UV-Vis spectroscopy in diffuse reflectance mode. The results suggest that the TiO2 structure was doped with the Mo6+ and Cu2+ ions in the position of the Ti4+. The x%MoS2/Cu/TiO2 samples presented lower band gap energy values and greater optical absorption in the visible region than the pure TiO2 sample. Lastly, the photocatalytic activity of the samples was assessed by means of the photodegradation of methylene blue under visible light. The results show that when the quantity of Mo in the co-doped samples increased (x%MoS2/Cu/TiO2) there were significant increases of up to 93% in the photocatalytic activity.


Assuntos
Cobre/química , Dissulfetos/química , Luz , Nanopartículas Metálicas/química , Azul de Metileno/química , Molibdênio/química , Titânio/química , Catálise , Fotólise , Água/química , Poluentes Químicos da Água/química , Purificação da Água , Difração de Raios X
11.
J Immunol Res ; 2016: 3845247, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27413759

RESUMO

Upon Mycobacterium tuberculosis infection, macrophages may undergo apoptosis, which has been considered an innate immune response. The pathways underlying the removal of dead cells in homeostatic apoptosis have been extensively studied, but little is known regarding how cells that undergo apoptotic death during mycobacterial infection are removed. This study shows that macrophages induced to undergo apoptosis with mycobacteria cell wall proteins are engulfed by J-774A.1 monocytic cells through the mannose receptor. This demonstration was achieved through assays in which phagocytosis was inhibited with a blocking anti-mannose receptor antibody and with mannose receptor competitor sugars. Moreover, elimination of the mannose receptor by a specific siRNA significantly diminished the expression of the mannose receptor and the phagocytosis of apoptotic cells. As shown by immunofluorescence, engulfed apoptotic bodies are initially located in Rab5-positive phagosomes, which mature to express the phagolysosome marker LAMP1. The phagocytosis of dead cells triggered an anti-inflammatory response with the production of TGF-ß and IL-10 but not of the proinflammatory cytokines IL-12 and TNF-α. This study documents the previously unreported participation of the mannose receptor in the removal of apoptotic cells in the setting of tuberculosis (TB) infection. The results challenge the idea that apoptotic cell phagocytosis in TB has an immunogenic effect.


Assuntos
Apoptose , Parede Celular/imunologia , Lectinas Tipo C/fisiologia , Macrófagos/imunologia , Lectinas de Ligação a Manose/fisiologia , Monócitos/imunologia , Mycobacterium smegmatis/imunologia , Fagocitose , Receptores de Superfície Celular/fisiologia , Animais , Linhagem Celular Tumoral , Vesículas Extracelulares/ultraestrutura , Imunofluorescência , Interleucina-10/metabolismo , Interleucina-12/metabolismo , Lectinas Tipo C/genética , Proteínas de Membrana Lisossomal/genética , Proteínas de Membrana Lisossomal/metabolismo , Macrófagos/citologia , Macrófagos/microbiologia , Receptor de Manose , Lectinas de Ligação a Manose/genética , Camundongos , Mycobacterium smegmatis/crescimento & desenvolvimento , Fagossomos/imunologia , Fagossomos/ultraestrutura , RNA Interferente Pequeno , Receptores de Superfície Celular/genética , Fator de Crescimento Transformador beta/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Proteínas rab5 de Ligação ao GTP/análise
12.
Nanoscale ; 7(14): 6216-29, 2015 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-25779372

RESUMO

This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb(2+) position with Sn(2+), Sr(2+), Cd(2+) and Ca(2+). The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn(2+), Sr(2+) and Cd(2+) did not modify the normal tetragonal phase. When doping with Ca(2+), the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr(2+) < Cd(2+) < Ca(2+) < CH3NH3PbI3 ≈ Sn(2+). The biggest decrease was generated by Sr(2+), which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn(2+) ≈ Pb(2+) > Cd(2+) > Sr(2+) for the tetragonal structure and Pb(2+) > Ca(2+) for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn(2+)-doped tetragonal structures, which were different from those doped with Sr(2+) and Cd(2+). Furthermore, when Cd(2+) was incorporated, the Cd-I interaction was strengthened. For Ca(2+) doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.

13.
Beilstein J Nanotechnol ; 6: 605-16, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25821701

RESUMO

Tm-doped TiO2 nanoparticles were synthesized using a water-controlled hydrolysis reaction. Analysis was performed in order to determine the influence of the dopant concentration and annealing temperature on the phase, crystallinity, and electronic and optical properties of the resulting material. Various characterization techniques were utilized such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. For the samples annealed at 773 and 973 K, anatase phase TiO2 was obtained, predominantly internally doped with Tm(3+). ICP-AES showed that a doping concentration of up to 5.8 atom % was obtained without reducing the crystallinity of the samples. The presence of Tm(3+) was confirmed by X-ray photoelectron spectroscopy and UV-vis spectroscopy: the incorporation of Tm(3+) was confirmed by the generation of new absorption bands that could be assigned to Tm(3+) transitions. Furthermore, when the samples were annealed at 1173 K, a pyrochlore phase (Tm2Ti2O7) mixed with TiO2 was obtained with a predominant rutile phase. The photodegradation of methylene blue showed that this pyrochlore phase enhanced the photocatalytic activity of the rutile phase.

14.
Trans R Soc Trop Med Hyg ; 109(2): 159-67, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25604767

RESUMO

BACKGROUND: Integrated vector management strategies depend on local eco-bio-social conditions, community participation, political will and inter-sectorial partnership. Previously identified risk factors for persistent Triatoma dimidiata infestation include the presence of rodents and chickens, tiled roofs, dirt floors, partial wall plastering and dog density. METHODS: A community-based intervention was developed and implemented based on cyclical stakeholder and situational analyses. Intervention implementation and evaluation combined participatory action research and cluster randomized pre-test post-test experimental designs. The intervention included modified insecticide application, education regarding Chagas disease and risk factors, and participatory rodent control. RESULTS: At final evaluation there was no significant difference in post-test triatomine infestation between intervention and control, keeping pre-test rodent and triatomine infestations constant. Knowledge levels regarding Chagas disease and prevention practices including rodent control, chicken management and health service access increased significantly only in intervention communities. The odds of nymph infection and rat infestation were 8.3 and 1.9-fold higher in control compared to intervention communities, respectively. CONCLUSION: Vector control measures without reservoir control are insufficient to reduce transmission risk in areas with persistent triatomine infestation. This integrated vector management program can complement house improvement initiatives by prioritizing households with risk factors such as tiled roofs. Requirement for active participation and multi-sectorial coordination poses implementation challenges.


Assuntos
Doença de Chagas/prevenção & controle , Galinhas/parasitologia , Doenças do Cão/parasitologia , Doenças das Aves Domésticas/parasitologia , Triatoma/parasitologia , Trypanosoma cruzi/patogenicidade , Animais , Doença de Chagas/transmissão , Participação da Comunidade , Doenças do Cão/transmissão , Cães , Exposição Ambiental/efeitos adversos , Exposição Ambiental/prevenção & controle , Guatemala/epidemiologia , Conhecimentos, Atitudes e Prática em Saúde , Habitação/normas , Humanos , Controle de Insetos , Inseticidas , Doenças das Aves Domésticas/transmissão , Ratos , Fatores de Risco , Trypanosoma cruzi/isolamento & purificação
15.
Nanoscale ; 6(21): 12740-57, 2014 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-25219888

RESUMO

This is an experimental and theoretical study of thulium doped TiO2 nanoparticles. From an experimental perspective, a method was used to synthesize thulium-doped TiO2 nanoparticles in which Tm(3+) replaces Ti(4+) in the lattice, which to our knowledge has neither been reported nor studied theoretically so far. Different proportions of anatase and rutile phases were obtained at different annealing temperatures, and XRD and Raman spectroscopy also revealed the presence of a pyrochlore phase (Tm2Ti2O7) at 1173 K. Thus, the structure of the Tm-doped nanoparticles was thermally-controlled. Furthermore, XPS showed the presence of Tm(3+) in the samples synthesized, which produces oxygen vacancies to maintain the local neutrality in the lattice. The presence of Tm(3+) in the samples led to changes in the UV-Vis absorption spectra, so they showed photoluminescence properties and new states in the band gap, which produce a new lower energy electronic transition than the main TiO2 one. Periodic DFT calculations were performed to understand the experimentally produced structures. The production of oxygen vacancies was analysed and the changes generated in the structure were fully detailed. The DOS and PDOS analyses confirmed the experimental results obtained using UV-Vis spectroscopy, and showed that the new electronic states in the band gap are due to interactions of the f state of Tm and the p state of O. Likewise, the charge study and the ELF analysis indicate that when Tm is introduced into the TiO2 structure, the Ti-O bond around the oxygen vacancy is strengthened. Finally, an example of a photocatalytic application was developed to show the high efficiency of the samples due to the heterojunction in the interfaces of the phases in the samples, which improved the charge separation and the good charge carrier mobility due to the presence of the pyrochlore phase, as was also shown theoretically.

16.
Chemphyschem ; 15(11): 2267-80, 2014 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-24840394

RESUMO

This study presents the experimental and theoretical study of highly internally Al-doped TiO2 nanoparticles. Two synthesis methods were used and detailed characterization was performed. There were differences in the doping and the crystallinity, but the nanoparticles synthesized with the different methods share common features. Anatase to rutile transformation occurred at higher temperatures with Al doping. X-ray photoelectron spectroscopy showed the generation of oxygen vacancies, which is an interesting feature in photocatalysis. In turn, the band-gap energy and the valence band did not change appreciably. Periodic density functional calculations were performed to model the experimentally doped structures, the formation of the oxygen vacancies, and the band gap. Calculation of the density of states confirmed the experimental band-gap energies. The theoretical results confirmed the presence of Ti(4+) and Al(3+) . The charge density study and electron localization function analysis indicated that the inclusion of Al in the anatase structure resulted in a strengthening of the TiO bonds around the vacancy.

17.
Phys Chem Chem Phys ; 16(8): 3835-45, 2014 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-24434807

RESUMO

A good correlation was obtained between the electronic properties of Cu-doped anatase TiO2 by virtue of both physical chemistry characterization and theoretical calculations. Pure and Cu-doped TiO2 were synthesized. The composition, structural and electronic properties, and the band gap energy were obtained using several techniques. The method of synthesis used produces Cu-doped anatase TiO2, and XRD, XPS and Raman spectroscopy indicate that Cu atoms are incorporated in the structure by substitution of Ti atoms, generating a distortion of the structure and oxygen vacancies. In turn, the band gap energy of the synthesized samples decrease drastically with the Cu doping. Moreover, periodic density functional theory (DFT-periodic) calculations were carried out both to model the experimentally observed doped structures and to understand theoretically the experimental structures obtained, the formation of oxygen vacancies and the values of the band gap energy. From the analysis of density of states (DOS), projected density of states (PDOS) and the electron localization function (ELF) a decrease in the band gap is predicted upon increasing the Cu doping. Thus, the inclusion of Cu in the anatase structure implies a covalent character in the Cu-O interaction, which involves the appearance of new states in the valence band maximum with a narrowing in the band gap.

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