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1.
Neural Regen Res ; 16(1): 143-149, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32788469

RESUMO

Veins are easy to obtain, have low immunogenicity, and induce a relatively weak inflammatory response. Therefore, veins have the potential to be used as conduits for nerve regeneration. However, because of the presence of venous valves and the great elasticity of the venous wall, the vein is not conducive to nerve regeneration. In this study, a novel tissue engineered nerve graft was constructed by combining normal dissected nerve microtissue with an autologous vein graft for repairing 10-mm peripheral nerve defects in rats. Compared with rats given the vein graft alone, rats given the tissue engineered nerve graft had an improved sciatic static index, and a higher amplitude and shorter latency of compound muscle action potentials. Furthermore, rats implanted with the microtissue graft had a higher density and thickness of myelinated nerve fibers and reduced gastrocnemius muscle atrophy compared with rats implanted with the vein alone. However, the tissue engineered nerve graft had a lower ability to repair the defect than autogenous nerve transplantation. In summary, although the tissue engineered nerve graft constructed with autologous vein and nerve microtissue is not as effective as autologous nerve transplantation for repairing long-segment sciatic nerve defects, it may nonetheless have therapeutic potential for the clinical repair of long sciatic nerve defects. This study was approved by the Experimental Animal Ethics Committee of Chinese PLA General Hospital (approval No. 2016-x9-07) on September 7, 2016.

2.
Food Chem ; 338: 128115, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33092006

RESUMO

Citrus flavonoids consist of diverse analogs and possess various health-promoting effects dramatically depending on their chemical structures. Since different flavonoids usually co-exist in real samples, it's necessary to develop rapid and efficient methods for simultaneous determination of multiple flavonoids. Thin layer chromatography combined with surface enhanced Raman spectroscopy (TLC-SERS) was established to simultaneously separate and detect 14 citrus flavonoids for the first time. These target compounds could be characterized and discriminated when paired with SERS at 6-500 times greater the sensitivity than TLC alone. TLC-SERS exhibited high recovery rates (91.5-121.7%) with relative standard deviation lower than 20.8%. Moreover, the established TLC-SERS method was successfully used to simultaneously detect multiple flavonoids in real samples, which exhibited comparable accuracy to high performance liquid chromatography with shorter analytical time (10 vs 45 min). All the results demonstrated that this could be a promising method for simultaneous, rapid, sensitive and accurate detection of flavonoids.

3.
J Nanosci Nanotechnol ; 21(2): 1272-1277, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33183472

RESUMO

Myocardial infarction is one of the common types of coronary heart disease in the clinic. Its morbidity, lethality and disability are high, and it has become a serious threat to human health. At present, it is shown that in the early stage of acute myocardial infarction, myocardial cells are mainly apoptotic, suggesting that effectively blocking myocardial apoptosis in the early stage of myocardial infarction is of great significance for reducing tissue necrosis in the infarcted area. Recent studies have shown that NG nano-protein complexes have a better therapeutic effect on acute myocardial infarction and can inhibit left ventricular remodeling in patients with acute myocardial infarction. However, there are few studies on the effect of NG nano-protein complexes on myocardial cell apoptosis after ischemia. This study used a rat model of acute myocardial infarction to analyze its effect on apoptotic proteins of myocardial cells in rats with acute myocardial infarction in order to provide a certain theoretical basis for its clinical application. In this study, 45 SD rats were randomly divided into a sham operation group, a myocardial infarction group, and a NG nano-protein complex group, with 15 in each group. The sham operation group only underwent thoracotomy, and received normal saline gavage postoperatively; the myocardial infarction group and the NG nano-protein complex group were ligated to the left anterior descending coronary artery of the rat to establish an acute myocardial infarction model, and were performed separately treatment with saline and NG nanoprotein complexes. Finally, we conclude that this nano-protein complex can significantly reduce the expression level of myocardial apoptosis-related proteins in rats with acute myocardial infarction, and is of great significance in inhibiting the apoptosis of acute myocardial infarction cells.

4.
JMIR Form Res ; 4(11): e21995, 2020 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-33151149

RESUMO

BACKGROUND: Although researchers are giving increased attention to blockchain-based personal health records (PHRs) and data sharing, the majority of research focuses on technical design. Very little is known about health care consumers' intentions to adopt the applications. OBJECTIVE: This study aims to explore the intentions and concerns of health care consumers regarding the adoption of blockchain-based personal health records and data sharing. METHODS: Three focus groups were conducted, in which 26 participants were shown a prototype of a user interface for a self-sovereign blockchain-based PHR system (ie, a system in which the individual owns, has custody of, and controls access to their personal health information) to be used for privacy and secure health data sharing. A microinterlocutor analysis of focus group transcriptions was performed to show a descriptive overview of participant responses. NVivo 12.0 was used to code the categories of the responses. RESULTS: Participants did not exhibit a substantial increase in their willingness to become owners of health data and share the data with third parties after the blockchain solution was introduced. Participants were concerned about the risks of losing private keys, the resulting difficulty in accessing care, and the irrevocability of data access on blockchain. They did, however, favor a blockchain-based PHR that incorporates a private key recovery system and offers a health wallet hosted by government or other positively perceived organizations. They were more inclined to share data via blockchain if the third party used the data for collective good and offered participants nonmonetary forms of compensation and if the access could be revoked from the third party. CONCLUSIONS: Health care consumers were not strongly inclined to adopt blockchain-based PHRs and health data sharing. However, their intentions may increase when the concerns and recommendations demonstrated in this study are considered in application design.

5.
Int J Hyperthermia ; 37(1): 1279-1286, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33198563

RESUMO

BACKGROUND: Acute renal impairment (ARI) is a major complication after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) for cancer patients with peritoneal metastases. This study aimed to investigate the incidence and identify the risk factors of post-HIPEC creatinine increased. METHODS: From April 2015 to December 2019, demographic and perioperative data of 169 patients undergoing CRS/HIPEC with a preoperative creatinine level <1.5 mg/dL were retrospectively reviewed. Renal impairment was defined according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0. The risk factors of creatinine increased were analyzed using univariate and multiple logistic regression analyses. RESULTS: Among the 169 enrolled patients, 21 (12.4%) had postoperative creatinine increased (ARI group) and 148 (87.6%) did not (non-ARI group). Significantly more of the ARI group received a cisplatin HIPEC regimen than the non-ARI group (71.4 vs. 37.8%, p = 0.004). Multiple logistic regression analysis revealed that the patients who received a cisplatin HIPEC regimen (adjusted odds ratio [AOR] = 11.38, p < 0.001) and peritoneal dialysis solution as HIPEC perfusate (AOR = 7.07, p = 0.002) were more likely to develop post-HIPEC creatinine increased. CONCLUSIONS: Identifying the risk factors of post-HIPEC creatinine increased can help to improve patient selection, a dose of HIPEC regimens modification and perioperative care. We also identified the detrimental renal effect of peritoneal dialysis solution as HIPEC perfusate. More prospective studies are warranted to confirm these findings.

6.
Breast ; 54: 139-147, 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-33049657

RESUMO

PURPOSE: To investigate the outcomes of adjuvant whole breast radiation therapy (WBRT) in patients with invasive ductal carcinoma of the breast (breast IDC) receiving preoperative systemic therapy (PST) and breast-conserving surgery (BCS), and their prognostic factors, considering overall survival (OS), locoregional recurrence (LRR), distant metastasis (DM), and disease-free survival. PATIENTS AND METHODS: Patients diagnosed as having breast IDC and receiving PST followed by BCS were recruited and categorized by treatment into non-breast radiation therapy [BRT] (control) and WBRT (case) groups, respectively. Cox regression analysis was used to calculate hazard ratios (HRs) and confidence intervals (CIs). RESULTS: Multivariate Cox regression analyses indicated that non-BRT, cN3, and pathologic residual tumor (ypT2-4) or nodal (ypN2-3) stages were poor prognostic factors for OS. The adjusted HRs (aHRs; 95% CIs) of the WBRT group to non-BRT group for all-cause mortality were 0.14 (0.03-0.81), 0.32 (0.16-0.64), 0.43 (0.23-0.79), 0.23 (0.13-0.42), 0.52 (0.20-1.33), and 0.34 (0.13-0.87) in the ypT0, ypT1, ypT2-4, ypN0, ypN1, and ypN2-3 stages, respectively. The aHRs (95% CIs) of the WBRT group to non-BRT group for all-cause mortality were 0.09 (0.00-4.07), 0.46 (0.26-0.83), 0.18 (0.06-0.51), 0.28 (0.06-1.34), 0.25 (0.10-0.63), 0.47 (0.23-0.88), and 0.32 in the cT0-1, cT2, cT3, cT4, cN0, cN1, and cN2-3 stages, respectively. The WBRT group exhibited significantly better LRR-free and DM-free survival than the non-BRT group, regardless of the clinical T or N stage or pathologic response after PST. CONCLUSION: WBRT might lead to superior OS and LRR-free and DM-free survival compared with the non-BRT group, regardless of the initial clinical TN stage or pathologic response.

7.
Sci Rep ; 10(1): 16943, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-33037234

RESUMO

Mutations that lead to constitutive activation of key regulators in cellular processes are one of the most important drivers behind vigorous growth of cancer cells, and are thus prime targets in cancer treatment. BRAF V600E mutation transduces strong growth and survival signals for cancer cells, and is widely present in various types of cancers including lung cancer. A combination of BRAF inhibitor (dabrafenib) and MEK inhibitor (trametinib) has recently been approved and significantly improved the survival of patients with advanced NSCLC harboring BRAF V600E/K mutation. To improve the detection of BRAF V600E/K mutation and investigate the incidence and clinicopathological features of the mutation in lung cancer patients of southern Taiwan, a highly sensitive and specific real-time quantitative PCR (RT-qPCR) method, able to detect single-digit copies of mutant DNA, was established and compared with BRAF V600E-specific immunohistochemistry. Results showed that the BRAF V600E mutation was present at low frequency (0.65%, 2/306) in the studied patient group, and the detection sensitivity and specificity of the new RT-qPCR and V600E-specific immunohistochemistry both reached 100% and 97.6%, respectively. Screening the BRAF V600E/K mutation with the RT-qPCR and V600E-specific immunohistochemistry simultaneously could help improve detection accuracy.

9.
J Formos Med Assoc ; 2020 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-32873465

RESUMO

BACKGROUND/PURPOSE: Ropeginterferon alpha-2b (Ropeg) is a novel pegylated interferon-alpha recently approved for the treatment of polycythemia vera (PV) in Europe. However, other than data from clinical trials, little is known about this agent in real world practice. METHODS: A compassionate use program employing Ropeg for treating patients with unmet medical need was initiated in Taiwan in 2017. Herein, we collected clinical data and assessed the safety as well as efficacy of Ropeg in nine patients treated in this program. RESULTS: Collectively, among evaluable patients, both the molecular response and complete blood count remission rates were 62.5%. Most therapy-related side effects were mild, and there was no treatment discontinuation attributable to intolerable adverse events. The agent also showed efficacy in symptom amelioration and spleen size reduction. Although no specific patterns of cytokine level alteration could be identified, significantly attenuated plasma levels of inflammation markers were observed in one particular patient who happened to have normalized spleen size and most remarkable reduction in JAK2 mutant allele burden, indicating all-around improvement in every aspect of this case. Furthermore, plasma hepcidin levels increased in two-thirds of PV patients, illustrating the potential of Ropeg to restore normal regulation of erythropoiesis. Using RNA sequencing on pre- and post-treatment samples from one patient, we demonstrated altered expression of genes participating in IFN response, inflammation, apoptosis, and cellular differentiation. CONCLUSION: Conclusively, observed signs of efficacy and safety in our real-world experience prove Ropeg as a promising option for the treatment of MPN.

10.
Platelets ; : 1-8, 2020 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-32967492

RESUMO

Hepatitis C virus-associated immune thrombocytopenia (HCV-ITP) has been assumed to be one of secondary ITP and associated with antiplatelet antibodies. This study was to clarify the antibody profile in HCV-ITP compared with primary ITP. We enrolled 55 HCV-ITP, 30 primary ITP, 11 Helicobacter pylori-ITP, 21 HCV control, and 16 healthy volunteers. We reviewed their blood cell counts, autoimmune markers, and spleen size. We used enzyme-linked immunosorbent assay kit to detect the specific antibody to glycoproteins IIb/IIIa, Ia/IIa, Ib/IX, IV, and human leukocyte antigen (HLA) class I. Compared with primary ITP patients, HCV-ITP patients had an older age, lower white blood cell (WBC) count and fewer presented with severe thrombocytopenia. The rate of positive antibody detection was 63.6% for the HCV-ITP group higher than the rate of 40% for the primary ITP. In the HCV control, antiplatelet antibodies were detected in 38.1% patients and no one had more than two types of antibodies. The antiplatelet antibodies correlated to severer thrombocytopenia. An HLA class I antibody was associated with lower WBCs and larger spleen. In conclusion, HCV-ITP patients had a high rate of positive antiplatelet antibody. The antibodies were associated with not only lower platelets but also leukopenia and splenomegaly.

11.
Chemistry ; 2020 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-32969106

RESUMO

The convenient cross-coupling of sp 2 or sp 3 carbons with a specific boron vertex on carborane cage represents significant synthetic values and insurmountable challenges. In this work, we report a Rh-catalyzed reaction between o -carborane and N -acyl-glutarimides to construct various B cage - C bonds. Under the optimized condition, the removable imine directing group (DG) leads to B(3)- or B(3,6)-C couplings, while the pyridyl DG leads to B(3,5)-Ar coupling. In particular, an unexpected rearrangement of amide reagent is observed in pyridyl directed B(4)-C(sp 3 ) formation. This scalable protocol has many advantages, including easy access, the use of cheap and widely available coupling agents, no requirement of an external ligand, base or oxidant, high efficiency, and a broad substrate scope. Leveraging the Rh I dimer and twisted amides, this method enables straightforward access to diversely substituted and therapeutically important carborane derivatives at boron site, and provides a highly valuable vista for carborane-based drug screening.

12.
Anal Chem ; 92(19): 13452-13461, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32900179

RESUMO

Drug-induced hepatic damage has drawn great attention on public health problems. Drugs are biotransformed in the liver by enzymatic processes, accompanied by the production of reactive free radicals, which is the main cause of drug-induced hepatotoxicity. However, the limited penetration of optics makes the use of current luminescence imaging more difficult for acquiring free radicals mapping for lesion location, when applied to whole-body imaging in vivo. In this work, we develop an activatable nanoprobe based on Prussian blue (PB) that can combine magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) for deep-tissue ONOO- imaging. We discover that ONOO- can oxidize FeII within PB into FeIII and meanwhile destroy the crystal structure of PB so that the strong absorption of PB at 710 nm that originated from the electron transferring between FeII and FeIII is greatly diminished. As a result, the reduced photoacoustic imaging (PA) signal of PB is able to function as an indicator for sensing ONOO-. Importantly, after reaction with ONOO-, the reduced size of PB results in the decrease of rotational correlation time (τR), leading to the activatable MRI signal for sensing ONOO-. Finally, we demonstrate that the PB nanoprobe is successfully able to image the variation of ONOO- in drug-induced hepatotoxicity in vivo by PAI and MRI bimodal imaging. Notably, the complementarity of such dual-modality imaging could not only endow our probes with better accuracy and higher penetration depth for visualizing of ONOO- in drug-induced liver injury but also provide anatomical structure to identify the injury area of livers.

13.
Breast ; 54: 70-78, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32947148

RESUMO

PURPOSE: To use pathologic indicators to determine which patients benefit from postmastectomy radiation therapy (PMRT) for breast cancer after neoadjuvant chemotherapy (NACT) and total mastectomy (TM). PATIENTS AND METHODS: We enrolled 4236 patients with breast invasive ductal carcinoma who received NACT followed by TM. Cox regression analysis was used to calculate hazard ratios (HRs) and confidence intervals; independent predictors were controlled for or stratified in the analysis. RESULTS: After multivariate Cox regression analyses, the adjusted HRs derived for PMRT for all-cause mortality were 0.65 (0.52-0.81, P < 0.0001) and 0.58 (0.47-0.71, P < 0.0001) in postchemotherapy pathologic tumor stages T2-4 (ypT3-4) and postchemotherapy pathologic nodal stages N2-3 (ypN2-3), respectively. Moreover, adjusted HRs derived for PMRT with all-cause mortality were 0.51 (0.38-0.69, P < 0.0001), 0.60 (0.40-0.88, P = 0.0096), and 0.64 (0.48-0.86, P = 0.0024) in pathological stages IIIA, IIIB, and IIIC, respectively. Additionally, the PMRT group showed significant locoregional control irrespective of the pathologic response, even ypT0, ypN0, or pathological complete response (pCR), compared with the No-PMRT group. The multivariate analysis showed no statistical differences between the PMRT and No-PMRT groups for distant metastasis-free survival in any pathologic response of ypT0-4, ypN0-3, and pathologic American Joint Committee on Cancer stages pCR to IIIC. CONCLUSION: For patients with breast cancer ypT3-4, ypN2-3, or pathologic stages IIIA-IIIC receiving NACT and TM, benefit from PMRT if it is associated with OS benefits, regardless of the clinical stage of the disease. Compared with No-PMRT, PMRT improved locoregional recurrence-free survival, even pCR, in patients with breast cancer receiving NACT and TM.

14.
Anal Chem ; 92(20): 13661-13666, 2020 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-32957776

RESUMO

Epigenome constitutes an important layer that regulates gene expression and dynamics during development and diseases. Extensive efforts have been made to develop epigenome profiling methods using a low number of cells and with high throughput. Chromatin immunoprecipitation (ChIP) is the most important approach for profiling genome-wide epigenetic changes such as histone modifications. In this report, we demonstrate microfluidic ChIPmentation (mu-CM), a microfluidic technology that enables profiling cell samples that individually do not generate enough ChIP DNA for sequencing library preparation. We used a simple microfluidic device to allow eight samples to be processed simultaneously. The samples were indexed differently using a tagmentation-based approach (ChIPmentation) and then merged for library preparation. A histone modification profile for each individual sample was obtained by demultiplexing the sequencing reads based on the indexes. Our technology allowed profiling 20 cells and is well suited for cell-type-specific studies using low-abundance tissues.

15.
Support Care Cancer ; 2020 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-32995998

RESUMO

BACKGROUND: Nutritional counseling is frequently overlooked in cancer patients with normal nutritional status. This study aimed to evaluate the impact of nutritional counseling in head and neck cancer (HNC) patients with normal nutritional status prior to concurrent chemoradiotherapy (CCRT). METHODS: A total of 243 patients with pretreatment normal nutritional status and locally advanced HNC receiving concurrent chemoradiotherapy (CCRT) at three medical centers were enrolled. All patients were retrospectively allocated into the early (≤ 2 weeks, n = 105, 43.2%), late (> 2 weeks, n = 102, 42.0%), and no nutritional counseling groups (n = 36, 14.8%) according to the time interval between the date of CCRT initiation and the first date of nutritional counseling for comparison. RESULTS: The 1-year overall survival rates were 95.0%, 87.5%, and 81.3% in the early, late, and no nutritional counseling groups (p = 0.035), respectively. The median body weight changes at end of CCRT were - 4.8% (range, - 13.3 to 8.7%), - 5.6% (range, - 21.9 to 5.6%), and - 8.6% (range, - 20.3 to 2.4%) in patients in the early, late, and no nutritional counseling groups, respectively. The early termination of chemotherapy rates and the incompletion rates of planned radiotherapy were 1.9% and 1.9%, 2.9%, and 2.0%, 13.9%, and 19.4% in patients in the early, late, and no nutritional counseling groups, respectively. CONCLUSIONS: Our findings strongly suggest that while some HNC patients may have pretreatment normal nutritional status, early nutritional counseling is nevertheless essential for the improvement of treatment tolerance and survival outcome.

16.
Nat Commun ; 11(1): 3928, 2020 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-32764644

RESUMO

Despite progress in small scale electrocatalytic production of hydrogen peroxide (H2O2) using a rotating ring-disk electrode, further work is needed to develop a non-toxic, selective, and stable O2-to-H2O2 electrocatalyst for realizing continuous on-site production of neutral hydrogen peroxide. We report ultrasmall and monodisperse colloidal PtP2 nanocrystals that achieve H2O2 production at near zero-overpotential with near unity H2O2 selectivity at 0.27 V vs. RHE. Density functional theory calculations indicate that P promotes hydrogenation of OOH* to H2O2 by weakening the Pt-OOH* bond and suppressing the dissociative OOH* to O* pathway. Atomic layer deposition of Al2O3 prevents NC aggregation and enables application in a polymer electrolyte membrane fuel cell (PEMFC) with a maximum r(H2O2) of 2.26 mmol h-1 cm-2 and a current efficiency of 78.8% even at a high current density of 150 mA cm-2. Catalyst stability enables an accumulated neutral H2O2 concentration in 600 mL of 3.0 wt% (pH = 6.6).

17.
Nanoscale ; 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32857075

RESUMO

The electronic transport and field emission properties of a single-crystalline GdB44Si2 nanowire are studied. The atomic structure and elemental composition of the GdB44Si2 nanowire are characterized by transmission electron microscopy (TEM) using atomic imaging, energy-dispersive X-ray spectroscopy (EDS), and electron energy-loss spectroscopic (EELS) mapping. The electrical conductivity of the single GdB44Si2 nanowire is in the range of 46.8-60.1 S m-1. The in situ TEM field emission measurement reveals that it has a low work function of 2.4 eV. To realize a converged electron emission, a field evaporation pretreatment was used to clean the emission surface and to make a sharpened tip. The field emission probe measurement results show that the electron emission from the sharp GdB44Si2 nanowire is converged to a single field emission spot and it has a work function of 2.6 eV which is in agreement with the in situ TEM measurement. The stability of field emission current is also very good with a fluctuation of 1.4% in 20 min. With a low work function and stable emission current, the GdB44Si2 nanowire shows great promise for field emission applications.

18.
Biomed Res Int ; 2020: 5043583, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32685495

RESUMO

Lumbar spinal stenosis (LSS) is a common disease in the elderly population; it has been reported that patients with LSS have an abnormal gait pattern due to symptom such as neurogenic intermittent claudication (NIC); however, no detailed reports exist on the plantar pressure distributions in LSS patients with NIC. To analysis the plantar pressure characteristics of LSS patients, the Footscan® pressure system was used to perform dynamic plantar pressure measurements in 20 LSS patients (age, 69.5 ± 7.2 years) before and after the occurrence of NIC. The contact time (CT), foot progression angle (FPA), pressure-time integral (PTI), and contact area (CA) were collected and compared between the LSS patients and age-matched healthy subjects in each measurement. The LSS group showed an increase in forefoot CT%, PTI, and CA% in both measurements compared with those in the control group. After the occurrence of NIC in the LSS group, CT%, PTI, and CA% of the forefoot increased further compared with those before the occurrence of NIC. In addition, after the occurrence of NIC, the PTI and CA% of the forefoot shifted from the medial foot to the lateral foot. The results suggested that the plantar pressure distributions of patients with LSS differs from normal subjects due to the posture of waking with lumbar forward flexion, and the forefoot bears a higher relative load. In addition, the occurrence of NIC could affect the plantar pressure distribution of the patients with LSS, predicting the patient's risk of falling to the anterior direction and to the symptomatic side.

19.
Nanoscale ; 12(32): 16770-16774, 2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32608436

RESUMO

A single hafnium carbide (HfC) nanowire field-induced electron emitter with a sharp tip apex is fabricated by Pt deposition and focused ion beam (FIB) milling. The structure of the electron emitter is characterized by scanning transmission electron microscopy (STEM) and atom probe tomography (APT). The HfC nanowire is single-crystalline with a thin oxide layer on its tip surface. The field emission properties are determined by using both in situ transmission electron microscopy (TEM) and a field-emission probe in a high-vacuum chamber. A high current of 173 nA was obtained at a low extraction voltage of 631 V with an emission gap of 5 mm. The emission current is stable at 60 nA for 100 min with a fluctuation of 0.7%. The deduced work function was 3.1 eV. It is suggested that the implanted Ga ions and the oxide layer induce more downward dipoles that are beneficial for lowering the work function and creating a stable surface. When the low keV FIB processing is applied, it takes within 30 minutes to finish a HfC nanowire emitter, establishing an efficient procedure for the preparation of nanowire emitters. These results provide a controllable and fast production method for the fabrication of single nanowire field-emission point electron sources.

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