RESUMO

This paper reports the competition of H2O (residual) and H2 by site (defects) on the Si surface, created by Xe+ ion bombardment. X-ray photoelectron spectroscopy (XPS) in an ultrahigh vacuum system attached to the sample preparation chamber provided the data for the analyses. As hydrogen cannot be detected by XPS, an indirect method to evaluate the O and H cover ratio was developed. The hydrogen passivation effect obtained by the formation of the Si-H bond due to H2 chemisorption limits Si-OH and Si-O-Si bonds, which are products of H2O dissociation. In addition, the results have shown that Xe+ ion bombardment diminished the H2 chemisorption energy barrier onto Si.

RESUMO

OBJECTIVES: This study evaluated the effectiveness of hydrogen peroxide (H2O2) as mouthwash and nasal spray on symptom relief in coronavirus disease 2019 (COVID-19) patients. METHODS: Patients positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), who were treated in a hospital or at home, and patients' family members (not positive for SARS-CoV-2), were randomized into 2 groups: experimental (1% H2O2 for gargling, 0.5% H2O2 for nasal wash), and control. Patients gargled the solution 3 times a day, and applied the nasal spray twice a day, for a 7-day period. Family members received the same treatment as the treated COVID-19 patient. The researchers contacted patients every 2 days over an 8-day period. An average post-treatment interval of 8 days passed before testing family members. RESULTS: The most frequent symptoms on day 0 were cough, loss of taste, and hyposmia; there were no significant differences between groups, independent of the period. The symptom of dyspnea presented a significant difference between days 2 and 4 (p<0.05). Among family members, 86.0% had no antibodies, 2.3% had antibodies, and 11.6% had active infections (4 in the experimental group and 6 in the control group). The most frequent adverse effects in the H2O2 group were a burning throat and nose. CONCLUSIONS: H2O2 was not effective for the relief of COVID-19 symptoms and was associated with reports of transient adverse effects.

Assuntos

COVID-19 , Peróxido de Hidrogênio , Brasil , Método Duplo-Cego , Humanos , SARS-CoV-2 , Resultado do Tratamento

RESUMO

OBJECTIVES: To evaluate the effectiveness of hydrogen peroxide (H2O2) in the form of mouthwash and nasal spray as an auxiliary treatment for coronavirus disease 2019 (COVID-19). METHODS: Forty hospitalized patients who tested positive for severe acute respiratory syndrome coronavirus 2 using a reverse-transcription polymerase chain reaction test were evaluated. They were randomly divided into an experimental group (n= 20; gargling with 1.0% H2O2 and nasal wash with 0.5% H2O2) or a control group (n= 20). The solutions were used for 7 days and the patients were monitored every 2 days, for a total of 8 days. At check-ups, patients were asked about their symptoms and possible adverse effects of the solutions. The presence and severity (mild, moderate, or severe) of symptoms were recorded. Data were compared using the Student test and the Fisher exact test (α= 0.05). RESULTS: There was no significant difference between the 2 groups in the length of hospital stay (p= 0.65). The most frequent symptom on day 0 was coughing (72.0% in the experimental group and 76.5% in the control group), which abated over time. There was no significant difference between the groups in the evaluated symptoms. Most (75.0%) of the patients in the experimental group presented a reduction in dyspnea between days 0 and 2. Few patients reported adverse effects from the use of the solutions. CONCLUSIONS: H2O2 as a mouthwash and nasal spray is safe to use. There is insufficient evidence to demonstrate that H2O2 is effective as an auxiliary treatment for hospitalized COVID-19 patients.

Assuntos

Anti-Infecciosos Locais/administração & dosagem , Tratamento Farmacológico da COVID-19 , Peróxido de Hidrogênio/administração & dosagem , SARS-CoV-2 , Adulto , Brasil , COVID-19/virologia , Método Duplo-Cego , Feminino , Hospitalização , Humanos , Masculino , Pessoa de Meia-Idade , Antissépticos Bucais/administração & dosagem , Sprays Nasais , Índice de Gravidade de Doença , Resultado do Tratamento

RESUMO

Hydrogenated amorphous carbon thin films (a-C:H) have attracted much attention because of their surprising properties, including ultralow friction coefficients in specific conditions. Adhesion of a-C:H films on ferrous alloys is poor due to chemical and physical aspects, avoiding a widespread application of such a film. One possibility to overcome this drawback is depositing an interlayer-an intermediate thin film-between the carbon-based coating and the substrate to improve chemical interaction and adhesion. Based on this, interlayers play a key role on a-C:H thin-film adhesion through a better chemical network structure at the outermost layer of the a-SiC x:H interlayer, i.e., the a-C:H/a-SiC x:H interface. However, despite the latest important advances on the subject, the coating adhesion continues being a cumbersome problem since it depends on multifactorial causes. Thus, the purpose of this paper is to report a standard protocol leading to surprising good results based on the control of the interfacial chemical bonding by properly biasing the substrate (between 500 and 800 V) during the a-SiC x:H interlayer deposition at an appropriate low temperature, by using hexamethyldisiloxane as precursor. The interlayers and the outermost interfaces were analyzed by a comprehensive set of techniques, including X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, and Fourier transform infrared spectroscopy. Nanoscratch tests, complemented by scanning electron microscopy and energy-dispersive X-ray spectroscopy, were used to evaluate the critical load for delamination to certify and quantify the adhesion improvement. This study was important to identify the chemical local bonding of the elements at the interface and its local environment, including the in-depth chemical composition profile of the coating. An important effect is that the oxygen content decreases on increasing substrate bias voltage, improving the adhesion of the film. This is due to the fact that energetic ion hitting the growing interlayer breaks Si-O and C-O bonds, augmenting the content of Si-C and C-C bonds at the outermost interface of the a-SiC x:H interlayer and enhancing the a-C:H coating adhesion. Moreover, the combination of high bias voltage (800 V) and low temperature (150 °C) during the a-SiC x:H interlayer deposition allows good adhesion of a-C:H thin films due to sputtering of light elements like oxygen. Therefore, an appropriated bias and temperature combination can open new pathways in a-C:H thin-film deposition at low temperatures. These results are particularly interesting for temperature-sensible metal alloys, where well-adhered a-C:H thin films are mandatory for tribological applications.