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1.
J Adv Nurs ; 2024 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-38332497

RESUMO

AIMS: To explore women's and health professionals' views on the development of a midwifery-led mHealth app intervention in antenatal care and their demands for app functionality. DESIGN: Descriptive qualitative research was utilized. METHODS: In total, 15 pregnant or postpartum women were interviewed via in-depth interviews and 10 health professionals including obstetricians, midwives and obstetric nurses were invited to participate in a focus group discussion (FGD). All interviews and the FGD were analysed using qualitative content analysis. RESULTS: Four key themes emerged from the data, including (1) limitations of current maternity care services; (2) potential benefits for mHealth app-based midwifery care; (3) possible challenges for providing midwifery care through mHealth apps and (4) suggestions and needs for developing a midwifery-led mHealth app. Participants agreed on the potential need of developing a midwifery-led mHealth app in antenatal care to increase access to midwifery care services and to meet women's diverse needs. Participants preferred to develop professional, reliable, full-featured and interactive mobile applications. The main functions of midwifery-led mHealth apps included personalized assessment and health education, self-monitoring and feedback, data sharing and interactive functions. Women mentioned that online communication and consultation with midwives could help them receive continuous support outside facilities. Health professionals expressed it would be of great convenience and timeliness to send personalized messages to women and to inform them of healthy lifestyles during pregnancy. The challenges included a shortage of human resources, medico-legal risks associated with mHealth and data security risks. CONCLUSIONS: This study explores the individual views and functional needs of target users and healthcare providers for developing a midwifery-led mHealth app in antenatal care, which will serve as a reference for future application development. IMPACT: Our study has important and practical implications for guiding the development of future midwifery-led mHealth app interventions. PATIENT OR PUBLIC CONTRIBUTION: No patient or public contribution.

2.
Appl Opt ; 61(31): 9124-9134, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-36607045

RESUMO

Image encryption has emerged as a method of disguising an image with a noisy or meaningless appearance to prevent its content from being accessed by unauthorized users. We propose an architecture named flexible image encryption and decryption ResNet (FEDResNet) for diffusing an image in end-to-end mode. The architecture consists of an encryption network for diffusing the image and a decryption network for restoring the plaintext image from the diffused image. To enhance the security of the encrypted image, the diffused image is further processed with two optional operations: parallel scrambling and serial diffusion. Two key planes are constructed based on a user-defined key with a chaotic map to control the authority to access images. The structure and parameters of FEDResNet can be shared publicly by different users; hence, it is more flexible and convenient than previous deep-learning-based image encryption methods. A classification network is trained to classify medical images in ciphertext environments. The proposed FEDResNet is trained and tested on the ImageNet data set. Extensive experiments have been performed, and the experimental results suggest that the proposed model can achieve a high level of security with satisfactory efficiency. The experimental results also show that FEDResNet-encrypted images can be classified directly in the ciphertext domain by authorized users as accurately as plaintext images, which is a superior property that is not possessed by traditional image encryption methods.

3.
BMC Pregnancy Childbirth ; 20(1): 423, 2020 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-32718307

RESUMO

An amendment to this paper has been published and can be accessed via the original article.

4.
BMC Pregnancy Childbirth ; 20(1): 386, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32616073

RESUMO

BACKGROUND: There is an increasing global trend towards the widespread over-medicalisation of labour and childbirth. The present study aimed to investigate pregnant women's clinical characteristics, intrapartum interventions, duration of labour and its associated factors; and to compare the differences of these variables between nulliparas and multiparas in China. METHODS: A multi-center cross-sectional study was carried out in three tertiary hospitals of Fudan University in Shanghai, China. A total of 1523 participants were approched and assessed for eligibility. Data on women's sociodemographic characteristics, intrapartum interventions, and duration of labour were measured and collected. Kaplan-Meier survival analysis was performed to present the curves of total duration of labour by parity. After z-transformation of labour duration, multivariable linear regression was used to control for confounding and to identify independent associations between potential associated factors and the primary outcome of labour duration. RESULTS: Overall, 1209 eligible women agreed to participate and were investigated. Rates of different intrapartum interventions were 27.4% in use of amniotomy, 37.9% in use of oxytocin, 53.0% in continuous electronic fetal monitoring, and 52.9% in epidural use, respectively. The curve of total duration of labour was significantly different between nulliparas and multiparas (P < .001). Of the 1209 participants, 983 (81.3%) women eventually achieved successful vaginal birth while 226 (18.7%) women ended in intrapartum caesarean section. The median duration of total stage of labour was significantly longer in the nulliparous group [9.38 (6.33,14.10) hours] than that in the multiparous group [5.08 (3.00,7.83) hours] (P < .001). The following factors were independently associated with longer duration of total stage of labour: epidural analgesia (P < .001), primiparity (P < .001), continuous electronic fetal monitoring (P = .035), and increased birth weight (P = .005). CONCLUSIONS: Intrapartum medical interventions become common obstetric practices in urban China. Multifactorial variables independently associated with longer duration of labour were identified, including epidural analgesia, primiparity, continuous electronic fetal monitoring, and increased birth weight. Further research is required to validate these variables and to determine the modifiable factors for labour management. And models of care with lower intervention rates such as midwife-led models of care should be developed and implemented in China.


Assuntos
Parto Obstétrico/estatística & dados numéricos , Trabalho de Parto , Adulto , Analgesia Epidural/estatística & dados numéricos , Peso ao Nascer , Índice de Massa Corporal , Cardiotocografia , Cesárea/estatística & dados numéricos , China , Estudos Transversais , Feminino , Ganho de Peso na Gestação , Humanos , Primeira Fase do Trabalho de Parto , Segunda Fase do Trabalho de Parto , Terceira Fase do Trabalho de Parto , Pessoa de Meia-Idade , Ocitocina/uso terapêutico , Paridade , Parto , Gravidez , Adulto Jovem
5.
7.
Biol Pharm Bull ; 37(1): 37-43, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24389479

RESUMO

Zorro2 is a member of a non-long terminal repeat (LTR) retrotransposon family in Candida albicans, but as yet no clear evidence has been provided to establish either transcription or transposition activity for Zorro2. In this study, the relative expression changes of two open reading frames in Zorro2, ORF19.7274 and ORF19.7275, were examined in response to miconazole (MCZ), and were found to be increased by this treatment. As well, the copy number and the transcripts of Zorro2 in MCZ-induced resistant daughter strains were increased compared to the parental strain, indicating that transposition of Zorro2 occurred during long-term MCZ treatment. Intriguingly, the transcription activity of Zorro2 retrotransposons was significantly inhibited when the cells were treated with MCZ together with antioxidant N-acetyl-L-cysteine (NAC). As both the level of intracellular reactive oxygen species (ROS) and the expression of genes involving DNA repair activated by MCZ were reduced when combined with the treatment of NAC, we propose that the damage caused by accumulation of ROS under MCZ stress is a major reason for the transcription and transposition activation of the Zorro2 retrotransposon.


Assuntos
Antifúngicos/farmacologia , Candida albicans/efeitos dos fármacos , Miconazol/farmacologia , Fases de Leitura Aberta , Espécies Reativas de Oxigênio/metabolismo , Retroelementos , Transcrição Gênica , Acetilcisteína/farmacologia , Antioxidantes/farmacologia , Candida albicans/genética , Reparo do DNA , Genoma Fúngico
8.
BMJ Open ; 14(5): e082527, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38692722

RESUMO

OBJECTIVE: To investigate the status of the midwifery workforce and childbirth services in China and to identify the association between midwife staffing and childbirth outcomes. DESIGN: A descriptive, multicentre cross-sectional survey. SETTING: Maternity hospitals from the eastern, central and western regions of China. PARTICIPANTS: Stratified sampling of maternity hospitals between 1 July and 31 December 2021.The sample hospitals received a package of questionnaires, and the head midwives from the participating hospitals were invited to fill in the questionnaires. RESULTS: A total of 180 hospitals were selected and investigated, staffed with 4159 midwives, 412 obstetric nurses and 1007 obstetricians at the labour and delivery units. The average efficiency index of annual midwifery services was 272 deliveries per midwife. In the sample hospitals, 44.9% of women had a caesarean delivery and 21.4% had an episiotomy. Improved midwife staffing was associated with reduced rates of instrumental vaginal delivery (adjusted ß -0.032, 95% CI -0.115 to -0.012, p<0.05) and episiotomy (adjusted ß -0.171, 95% CI -0.190 to -0.056, p<0.001). CONCLUSION: The rates of childbirth interventions including the overall caesarean section in China and the episiotomy rate, especially in the central region, remain relatively high. Improved midwife staffing was associated with reduced rates of instrumental vaginal delivery and episiotomy, indicating that further investments in the midwifery workforce could produce better childbirth outcomes.


Assuntos
Cesárea , Parto Obstétrico , Tocologia , Humanos , China/epidemiologia , Estudos Transversais , Feminino , Gravidez , Tocologia/estatística & dados numéricos , Adulto , Cesárea/estatística & dados numéricos , Parto Obstétrico/estatística & dados numéricos , Resultado da Gravidez/epidemiologia , Inquéritos e Questionários , Admissão e Escalonamento de Pessoal/estatística & dados numéricos , Maternidades/estatística & dados numéricos , Episiotomia/estatística & dados numéricos , Serviços de Saúde Materna/estatística & dados numéricos , Serviços de Saúde Materna/provisão & distribuição , Recursos Humanos/estatística & dados numéricos
9.
Nat Commun ; 15(1): 5541, 2024 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-38956044

RESUMO

To enhance the reaction kinetics without sacrificing activity in porous materials, one potential solution is to utilize the anisotropic distribution of pores and channels besides enriching active centers at the reactive surfaces. Herein, by designing a unique distribution of oriented pores and single crystalline array structures in the presence of abundant acid sites as demonstrated in the ZSM-5 nanorod arrays grown on monoliths, both enhanced dynamics and improved capacity are exhibited simultaneously in propene capture at low temperature within a short duration. Meanwhile, the ZSM-5 array also helps mitigate the long-chain HCs and coking formation due to the enhanced diffusion of reactants in and reaction products out of the array structures. Further integrating the ZSM-5 array with Co3O4 nanoarray enables comprehensive propene removal throughout a wider temperature range. The array structured film design could offer energy-efficient solutions to overcome both sorption and reaction kinetic restrictions in various solid porous materials for various energy and chemical transformation applications.

10.
Chemistry ; 19(20): 6265-73, 2013 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-23494813

RESUMO

A new polyaniline (PANI)-functionalized graphene oxide (GO-PANI) was prepared by using an in situ oxidative graft polymerization of aniline on the surface of GO. Its highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), ionization potential (IP), and electron affinity (EA) values experimentally estimated by the onset of the redox potentials were -5.33, -3.57, 5.59, and 3.83 eV, respectively. A bistable electrical-switching effect was observed in electronic device with the GO-PANI film sandwiched between the indium tin oxide (ITO) and Al electrodes. This device exhibited two accessible conductivity states, that is, the low-conductivity (OFF) state and the high-conductivity (ON) state, and can be switched to the ON state under a negative electrical sweep, and can also be reset to the initial OFF state by a reverse (positive) electrical sweep. The ON state is nonvolatile and can withstand a constant voltage stress of -1 V for 3 h and 10(8) read cycles at -1 V under ambient conditions. The nonvolatile nature of the ON state and the ability to write, read, and erase the electrical states, fulfill the functionality of a rewritable memory. An ON/OFF current ratio of more than 10(4) at -1 V achieved in this memory device is high enough to promise a low misreading rate through the precise control of the ON and OFF states. The mechanism associated with the memory effects was elucidated from molecular simulation results.

11.
Int J Nurs Stud ; 137: 104387, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36435003

RESUMO

BACKGROUND: Inappropriate weight gain during pregnancy may present risks for maternal and newborn health. Pregnancy is considered the optimal time to intervene on women's health behaviors such as eating habits and physical activity. However, current clinical practice guidelines for weight management during pregnancy were not fully based on randomized trials, thus lacking specific "active intervention ingredients" that are proven effective in achieving appropriate gestational weight gain. Therefore it is essential to develop and implement an evidence-based weight management program for pregnant women. OBJECTIVE: To examine the effects of a midwife-led weight management program on improving appropriate gestational weight gain, health literacy, experience of antenatal care, and maternal and neonatal outcomes among Chinese pregnant women. DESIGN: A two-group randomized controlled trial. SETTINGS AND PARTICIPANTS: A total of 426 pregnant women were recruited from a tertiary women's hospital in eastern China. METHODS: Participants were randomly allocated to either intervention group (n = 213) or control group (n = 213). Women in the intervention group participated in a midwife-led weight management program during pregnancy, while women in the control group received the conventional obstetrician-led antenatal care. We assessed women at the first antenatal contact, 35-36 weeks gestation and 2-3 days postpartum. Data on gestational weight gain, health literacy, experience of antenatal care, and maternal and neonatal outcomes were compared between the two groups. Dummy variable analysis was conducted to reveal the effect of weight management program on gestational weight gain. RESULTS: The overall gestational weight gain between the two groups was not statistically different (t = -1.377, P = 0.170). Compared with women in the control group, the odds of having inappropriate gestational weight gain was lower in the intervention group (OR = 0.270, 95%CI 0.169, 0.431). Further subgroup analyses showed that women in the intervention group had lower risk of inadequate gestational weight gain (OR = 0.305, 95%CI 0.180, 0.515) and excessive gestational weight gain (OR = 0.236, 95%CI 0.138, 0.404) than those in the control group. The score of experience of antenatal care was significantly higher in the midwife-led weight management group than that in the control group (193.70 ±â€¯18.51 versus 165.70 ±â€¯28.23, P < 0.001). Women's health literacy score was higher in the intervention group than control group [74.41 (69.57, 81.77) versus 71.88 (66.23, 77.18), P = 0.004]. CONCLUSION: Compared with the conventional antenatal care, the midwife-led weight management program could facilitate appropriate gestational weight gain, enhance health literacy, and promote positive experience of antenatal care for Chinese pregnant women.


Assuntos
Ganho de Peso na Gestação , Tocologia , Programas de Redução de Peso , Recém-Nascido , Feminino , Gravidez , Humanos , Gestantes , Cuidado Pré-Natal
12.
ACS Nano ; 17(13): 12603-12615, 2023 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-37350454

RESUMO

Despite much technical progress achieved so far, the exact surface and shape evolution during wet chemical etching is less unraveled, especially in ionically bonded ceramics. Herein, by using in situ liquid cell transmission electron microscopy, a repeated two-stage anisotropic and pulsating periodic etching dynamic is discovered during the pencil shape evolution of a single crystal ZnO nanorod in aqueous hydrochloric acid. Specifically, the nanopencil tip shrinks at a slower rate along [0001̅] than that along the ⟨101̅0⟩ directions, resulting in a sharper ZnO pencil tip. Afterward, rapid tip dissolution happens due to accelerated etching rates along various crystal directions. Concurrently, the vicinal base region of the original nanopencil tip emerges as a new tip followed by the repeated sequence of tip shrinking and removal. The high-index surfaces, such as {101̅m} (m = 0, 1, 2, or 3) and {21̅ 1̅n} (n = 0, 1, 2, or 3), are found to preferentially expose in different ratios. Our 3D electron tomography, convergent beam electron diffraction, middle-angle bright-field STEM, and XPS results indicate the dissociative Cl- species were bound to the Zn-terminated tip surfaces. Furthermore, DFT calculation suggests the preferential Cl- passivation over the {101̅1} and (0001) surfaces of lower energy than others, leading to preferential surface exposures and the oscillatory variation of different facet etching rates. The boosted reactivity due to high-index nanoscale surface exposures is confirmed by comparatively enhanced chemical sensing and CO2 hydrogenation activity. These findings provide an in-depth understanding of anisotropic wet chemical etching of ionic nanocrystals and offer a design strategy for advanced functional materials.

13.
PeerJ ; 10: e13965, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36193420

RESUMO

Background: Fatigue is one of the most prevalent symptoms among pregnant women. In patients with various diseases, pro-inflammatory cytokines are associated with fatigue; however, such associations are unknown in pregnant women. Objectives: The objective of this study was to examine the associations between pro-inflammatory cytokines and prenatal fatigue. Methods: A cross-sectional study was conducted on 271 pregnant Chinese women in their third trimester of pregnancy. Patient-reported Outcome Measurement Information System (PROMIS) was used to evaluate women's prenatal fatigue. Using enzyme-linked immunosorbent assay (ELISA), the serum concentrations of four pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1ß), interleukin 6 (IL-6) and interleukin 8 (IL-8), were measured. The data was analyzed by correlation analysis and general linear regression analysis. Results: In this sample, the mean (standard deviation) of fatigue scores was 51.94 (10.79). TNF-α (r = 0.21, p < 0.001), IL-6 (r = 0.134, p = 0.027) and IL-8 (r = 0.209, p = 0.001) were positively correlated to prenatal fatigue, although IL-1ß was not. TNF-α (ß = 0.263, p < 0.001), along with sleep quality (ß = 0.27, p < 0.001) and depression (ß = 0.376, p < 0.001) independently predicted prenatal fatigue. Conclusions: TNF-α was identified as an independent biomarker for prenatal fatigue in our study. Reducing pro-inflammatory cytokines may be a unique method for lowering prenatal fatigue and, consequently, enhancing mother and child health.


Assuntos
Citocinas , Interleucina-8 , Criança , Humanos , Feminino , Gravidez , Citocinas/análise , Gestantes , Fator de Necrose Tumoral alfa/análise , Interleucina-6/análise , Estudos Transversais , Fadiga/epidemiologia
14.
ACS Appl Mater Interfaces ; 14(13): 15370-15380, 2022 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-35319194

RESUMO

We present a simple, effective, and controllable method to uniformly thin down the thickness of as-exfoliated two-dimensional Bi2O2Se nanoflakes using Ar+ plasma treatment. Atomic force microscopy (AFM) images and Raman spectra indicate that the surface morphology and crystalline quality of etched Bi2O2Se nanoflakes remain almost unaffected. X-ray photoelectron spectra (XPS) indicate that the O and Se vacancies created during Ar+ plasma etching on the top surface of Bi2O2Se nanoflakes are passivated by forming an ultrathin oxide layer with UV O3 treatment. Moreover, a bottom-gate Bi2O2Se-based field-effect transistor (FET) was constructed to research the effect of thicknesses and defects on electronic properties. The on-current/off-current (Ion/Ioff) ratio of the Bi2O2Se FET increases with decreasing Bi2O2Se thickness and is further improved by UV O3 treatment. Eventually, the thickness-controlled Bi2O2Se FET achieves a high Ion/Ioff ratio of 6.0 × 104 and a high field-effect mobility of 5.7 cm2 V-1 s-1. Specifically, the variation trend of the Ion/Ioff ratio and the electronic transport properties for the bottom-gate Bi2O2Se-based FET are well described by a parallel resistor model (including bulk, channel, and defect resistance). Furthermore, the Ids-Vgs hysteresis and its inversion with UV irradiation were observed. The pulsed gate and drain voltage measurements were used to extract trap time constants and analyze the formation mechanism of different hysteresis. Before UV irradiation, the origin of clockwise hysteresis is attributed to the charge trapping/detrapping of defects at the Bi2O2Se/SiO2 interface and in the Bi2O2Se bulk. After UV irradiation, the large anticlockwise hysteresis is mainly due to the tunneling between deep-level oxygen defects in SiO2 and p++-Si gate, which implies the potential in nonvolatile memory.

15.
Chemistry ; 17(37): 10304-11, 2011 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-21805510

RESUMO

A new polymer, poly[{9,9-di(triphenylamine)fluorene}(9,9-dihexylfluorene)(4-aminophenylcarbazole)] (PFCz) was synthesized and used in a reaction with graphene oxide (GO) containing surface-bonded acyl chloride moieties to give a soluble GO-based polymer material GO-PFCz. A bistable electrical switching effect was observed in an electronic device in which the GO-PFCz film was sandwiched between indium-tin oxide (ITO) and Al electrodes. This device exhibited two accessible conductivity states, that is, a low-conductivity (OFF) state and a high-conductivity (ON) state, and can be switched to the ON state under a negative electrical sweep; it can also be reset to the initial OFF state by a reverse (positive) electrical sweep. The ON state is nonvolatile and can withstand a constant voltage stress of -1 V for 3 h and 10(8) read cycles at -1 V under ambient conditions. The nonvolatile nature of the ON state and the ability to write, read, and erase the electrical states, fulfill the functionality of a rewritable memory. The mechanism associated with the memory effects was elucidated from molecular simulation results and in-situ photoluminescence spectra of the GO-PFCz film under different electrical biases.

16.
Materials (Basel) ; 14(16)2021 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-34443021

RESUMO

The thick plate narrow gap welding of 25Cr2NiMo1V rotor steel is achieved by metal active gas arc welding, in which the weld gap was 18.04-19.9 mm. After welding, the weldment was heat treated at 580 °C (20 h). The impact and tensile properties in the as-welded and heat-treated were studied. The results show that after heat treatment, the coarse carbides in the center of the weld were transformed into fine granular carbides distributed along the grain boundaries, and the quantity of carbide precipitates in the weld near the fusion line was reduced. The tensile fracture mode changed from a ductile fracture to a combination of brittle and ductile fractures, and the tensile strength of the weld metal changed from 605 MPa to 543 MPa. After heat-treated, the radiation zone of the weld center changed from a brittle fracture to a combination of brittle and ductile fractures, and the impact energy changed from 141 J to 183 J; the characteristics of the brittle fracture in the radial zone of the fusion line were more obvious, and the impact energy changed from 113 J to 95 J. Therefore, after heat treatment, the toughness of the welded metal was improved, without reducing the strength and hardness of the welded metal to a large extent.

17.
Yao Xue Xue Bao ; 45(7): 821-6, 2010 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-20931777

RESUMO

Gene mutation of Candida albicans is one of the main causes for azole drug resistance. Different types of variation play different roles in promoting the process of drug resistance. ERG series of gene mutations primarily affect the ergosterol synthesis pathway. When the regulatory factors TAC1 for CDR1 gene and Mrr1 for MDR1 gene generate mutations, the expression level of drug efflux pump protein in Candida albicans may be changed. In addition, gene copy number variation is also gaining attention. Therefore, the research of mutation resistance-associated genes has a positive meaning to explore the mechanism of drug resistance in Candida albicans.


Assuntos
Antifúngicos/farmacologia , Azóis/farmacologia , Candida albicans/genética , Farmacorresistência Fúngica , Mutação/genética , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Candida albicans/efeitos dos fármacos , Sistema Enzimático do Citocromo P-450/genética , Variações do Número de Cópias de DNA , Proteínas Fúngicas/genética , Proteínas de Membrana Transportadoras/genética
18.
Nat Commun ; 11(1): 6404, 2020 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-33335090

RESUMO

Bulk photovoltaic effect (BPVE), featuring polarization-dependent uniform photoresponse at zero external bias, holds potential for exceeding the Shockley-Queisser limit in the efficiency of existing opto-electronic devices. However, the implementation of BPVE has been limited to the naturally existing materials with broken inversion symmetry, such as ferroelectrics, which suffer low efficiencies. Here, we propose metasurface-mediated graphene photodetectors with cascaded polarization-sensitive photoresponse under uniform illumination, mimicking an artificial BPVE. With the assistance of non-centrosymmetric metallic nanoantennas, the hot photocarriers in graphene gain a momentum upon their excitation and form a shift current which is nonlocal and directional. Thereafter, we demonstrate zero-bias uncooled mid-infrared photodetectors with three orders higher responsivity than conventional BPVE and a noise equivalent power of 0.12 nW Hz-1/2. Besides, we observe a vectorial photoresponse which allows us to detect the polarization angle of incident light with a single device. Our strategy opens up alternative possibilities for scalable, low-cost, multifunctional infrared photodetectors.

19.
ACS Appl Mater Interfaces ; 11(15): 14239-14248, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30920198

RESUMO

Growth of the large-sized and high-quality MoS2 single crystals for high-performance low-power electronic applications is an important step to pursue. Despite the significant improvement made in minimizing extrinsic MoS2 contact resistance based on interfacial engineering of the devices, the electron mobility of field-effect transistors (FETs) made of a synthetic monolayer MoS2 is yet far below the expected theoretical values, implying that the MoS2 crystal quality needs to be further improved. Here, we demonstrate the high-performance two-terminal MoS2 FETs with room-temperature electron mobility up to ∼90 cm2 V-1 s-1 based on the sulfurization growth of the bifunctional precursor, sodium molybdate dihydrate. This unique transition-metal precursor, serving as both the crystalline Mo source and seed promotor (sodium), could facilitate the lateral growth of the highly crystalline monolayer MoS2 crystals (edge length up to ∼260 µm). Substrate surface treatment with oxygen plasma prior to the deposition of the Mo precursor is fundamental to increase the wettability between the Mo source and the substrate, promoting the thinning and coalescence of the source clusters during the growth of large-sized MoS2 single crystals. The control of growth temperature is also an essential step to grow a strictly monolayer MoS2 crystal. A proof-of-concept for thermoelectric device integration utilizing monolayer MoS2 sheds light on its potential in low-voltage and self-powered electronics.

20.
ACS Nano ; 13(1): 913-921, 2019 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-30586289

RESUMO

Midinfrared (MIR), which covers numerous molecular vibrational fingerprints, has attracted enormous research interest due to its promising potential for label-free and damage-free sensing. Despite intense development efforts, the realization of waveguide-integrated on-chip sensing system has seen very limited success to date. The huge lattice mismatch between silicon and the commonly used detection materials such as HgCdTe, III-V, or II-VI compounds has been the key bottleneck that hinders their integration. Here, we realize an integration of silicon-on-insulator (SOI) waveguides with black phosphorus (BP) photodetectors. When operating near BP's cutoff wavelength where absorption is weak, the light-BP interaction is enhanced by exploiting the optical confinement in the Si waveguide and grating structure to overcome the limitation of absorption length constrained by the BP thickness. Devices with different BP crystal orientation and thickness are compared in terms of their responsivity and noise equivalent power (NEP). Spectral photoresponse from 3.68 to 4.03 µm was investigated. Additionally, power-dependent responsivity and gate-tunable photocurrent were also studied. At a bias of 1 V, the BP photodetector achieved a responsivity of 23 A/W at 3.68 µm and 2 A/W at 4 µm and a NEP less than 1 nW/Hz1/2 at room temperature. The integration of passive Si photonics and active BP photodetector is envisaged to offer a potential pathway toward the realization of integrated on-chip systems for MIR sensing applications.

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