Effect of strain on exciton dynamics in monolayer WS2

The exciton dynamics in a WS2 monolayer with strain are studied by transient absorption measurements.We measure the differential transmission signal from monolayer WS2 as a function of the probe wavelength at different levels of strain applied to the sample.The differential transmission spectrum has a positive maximum value at about 614 nm and shows no significant strain dependence.By time-resolving the differential transmission signal,we find that the strain has a minimal effect on the exciton formation process.However,the exciton lifetime is significantly reduced by strain.These results provide useful information for applications of WS2 in flexible electronic and optoelectronic devices where strain is inevitable.

Chemical vapor deposition growth of crystal monolayer SnS2 with NaCl-assistant

As an important member of the two-dimensional layers of metal dichalcogenides family, the two-dimensional(2 D)group IV metal chalcogenides(GIVMCs) have been attracting intensive attention. However, the growth of monolayer tin disulfide(SnS2) remains a great challenge contrasted to transition metal dichalcogenides, which have been studied quite maturely. Till date, there have been scant reports on the growth of large-scale and large-size monolayer SnS2. Here, we successfully synthesized monolayer SnS2 crystal on SiO2/Si substrates via NaCl-assisted CVD and the edge can be as long as 80 μm. Optical microscope, Raman spectroscopy, x-ray diffraction, atomic force microscopy(AFM), and energydispersion x-ray(EDX) were performed respectively to investigate the morphology, crystallographic structure, and optical property of the 2 D SnS2 nanosheets. In addition, we discussed the growing mechanism of the NaCl-assisted CVD method.

In situ growth of different numbers of gold nanoparticles on MoS_2 with enhanced electrocatalytic activity for hydrogen evolution reaction

Producing hydrogen through a hydrogen evolution reaction（HER） by splitting water at the suitable overpotential is a great alternative to solving the problems of environmental pollution and the energy crisis. Molybdenum sulfide（MoS2）has attracted extensive attention as one of the most promising catalytic materials for HER. In this work, we design a facile method to in situ grow gold nanoparticles（Au NPs） on MoS2. Different numbers of Au NPs with MoS2 are used to find the best catalytic activity. Due to the larger active surface area and higher conductivity of the Au–MoS2 composites, all the Au–MoS2 composites exhibit more enhanced HER electroactivity than pure MoS2. In brief, the new material architecture exhibits optimized HER activity with a low onset overpotential of 0.12 V, low Tafel slope of 0.163 V·dec^（-1）, and an excellent stability in acidic solution.

Analysis of the social and clinical factors affecting the age of children when receiving surgery for hypospadias:a retrospective study of 1611 cases in a single center

We aimed to explore the associations between the age at which children undergo surgery for hypospadias and a range of social and clinical factors in a single center.Our aim was to promote the early surgical treatment of children with hypospadias.For a 6-year period,social and clinical data were collected from all children undergoing surgery to repair hypospadias in Children’s Hospital of Chongqing Medical University(Chongqing,China),located in southwest of China.We analyzed the correlations between age at surgery and a range of social and clinical factors.A total of 1611 eligible cases were recruited,with a mean age of 54.3 months and a median age of 42 months:234 cases(14.5%)were classified into a“timely operation”group,419(26.0%)cases into a“subtimely operation”group,and 958(59.5%)cases into a“delayed operation”group.According to multivariate regression analyses,the higher the regional economic level,the closer the urethral opening to the perineum,and the higher the educational level of the guardians was,the younger the children were when they underwent the initial surgery for hypospadias;this was also the case for families without other children.Our subgroup analysis showed that the primary educational level of the guardians was a risk factor for subtimely surgery in their children(odds ratio[OR]=1.52,95%confidence interval[CI]:1.08-2.15,P<0.05).A lower regional economic level(OR=1.87,95%CI:1.26-2.78,P<0.01),a lower educational level of the guardians(OR=3.84,95%CI:2.31-6.41,P<0.01),and an anterior-segment urethral opening(OR_(1)[vs middle hypospadias]=2.07,95%CI:1.42-3.03;0R_(2)[vs posterior hypospadias]=2.63,95%CI:1.75-3.95;P<0.01)were all risk factors for delayed surgery in children.

Long-term follow-up results of testicular torsion in children

December 2020 to investigate the long-term follow-up results after testicular torsion(TT)in children.Boys with TT were divided into the salvage orchiopexy group and the orchiectomy group,and the baseline characteristics,ultrasonographic indications,intraoperative findings,testicular volumes,and adverse events during follow-up were compared.A total of 145 cases were included in this study.Approximately 56.6%of patients who underwent salvage orchiopexy had testicular atrophy(TA),and the median testicular volume loss of the testes was 57.4%.Age less than 6 years,delayed surgery,and intraoperative poor blood supply were associated with TA in pediatric TT after orchiopexy.Most atrophied testes appeared within 3-6 months after surgery.Compared with the corresponding age-matched healthy controls,the contralateral testicular volumes were larger in the orchiopexy(P=0.o01 without TA,and P=0.042 with TA)and orchiectomy groups(P=0.033).The adverse events were comparable in patients with orchiectomy or orchiopexy.In summary,follow-up before 3 months after surgery may not offer sufficient clinical value,while that 3 months after surgery should be regarded as the first follow-up time for testicular monitoring.The contralateral testes of patients with TT showed compensatory hypertrophy.We suggest performing orchiectomy when torsed testes are surgically assessed as Arda gradeⅢor inviable.