[Analysis on infectivity of COVID-19 patients before and after last negative nucleic acid test]

Objective: To investigate the infection rate in close contacts of COVID-19 patients before and after the last negative nucleic acid test, evaluate the effect of dynamic nucleic acid test in determining the infectivity of COVID-19 patients. Methods: Dynamic nucleic acid test results of COVID-19 cases were collected in a retrospective cohort study. COVID-19 cases with negative nucleic acid test results before their first positive nucleic acid tests were selected as study subjects. Close contacts of the index cases and the secondary close contacts were kept isolation for medical observation to assess their risk of infection. Results: This study included 89 confirmed cases from two local COVID-19 epidemics in Ningbo. A total of 5 609 close contacts were surveyed, the overall infection rate was 0.20%. No close contacts of the COVID-19 cases before the last negative nucleic acid test were infected, and the infection rate in the close contacts of the COVID-19 cases after the last negative nucleic acid test was 1.33%, all of these close contacts lived together with the index cases. No secondary close contacts were infected. Conclusion: COVID-19 patient becomes infectious after the last nucleic acid is negative, and has no infectivity before the last nucleic acid negative.

Revealing the synergistic mechanism of multiply nanostructured V2O3 hollow nanospheres integrated with doped N, Ni heteroatoms, in-situ grown carbon nanotubes and coated carbon nanolayers for the enhancement of lithium-sulfur batteries

Lithium sulfur (Li-S) batteries are regarded as one of the most promising future energy storage candidates on account of high theoretical specific capacity of 1675 mAh g^-1 and energy density of 2600 Wh kg^-1. However, their practical application is seriously hindered due to the poor conductivity and volume expansion of sulfur, the weak redox kinetics of lithium polysulfide (LPS), and the severe shuttle effect of LPS. Herein, V₂O₃@N,Ni-C nanostructures, multiply integrated with zero-dimensional (0D) V₂O₃ nanoparticles, 1D carbon nanotubes, 2D carbon coating layers and graphene, 3D hollow spheres, and doped N and Ni heteroatoms, were synthesized via a solvothermal method followed by chemical vapor deposition. After being used as a modifier for traditional commercial separator of Li-S batteries, the shuttle effect of LPS can be effectively suppressed owing to the abundant active physical and chemical adsorption sites derived from large specific surface area, rich porosity, and tremendous polarity of the V₂O₃ nanoparticles with multiple secondary nanostructure integration. Meanwhile, the transfer of Li⁺ ions and electrons can be effectively enhanced by the highly conductive 2D carbon network, and the kinetics of redox reaction (Li₂S_n ↔ Li₂S) can be accelerated by the doped N and Ni heteroatoms, leading to a synergistic promotion on the reutilization of the adsorbed LPS. Additionally, the unique 3D hollow structure can not only enhance the penetration of electrolyte, but also buffer the volume expansion of sulfur to some extent. Therefore, the rate capacity and cycling performance can be significantly enhanced by the multifunction synergism of adsorption, conductivity, catalysis, and volume buffering. An initial discharge capacity of 1590.4 mAh g^-1can be achieved at 0.1C, and the discharge capacity of 803.5 mAh g^-1can be still exhibited when increasing to 2C. After a long period of 500 cycles, additionally, the discharge specific capacity of 1142.2 mAh g^-1 and capacity attenuation of 0.0617% per cycle can be obtained at 1C.

[Effects of Porphyromonas gingivalis injected through tail vein on the expressions of biomarkers in neural stem cells and neurons of wild-type rats hippocampus]

Objectives: To study the effects of Porphyromonas gingivalis (Pg) injected through tail vein on the molecular expression levels of biomarkers of neural stem cells (NSC) and neurons in the hippocampus of wild-type adult rats, and the effects on hippocampal neurogenesis. Methods: Eighteen male Sprague-Dawley (SD) rats were randomly divided into 3 groups based on the table of random numbers (n=6 in each group). In low-intensity group and high-intensity group, rats were injected intravenously through tail vein with 200 μl Pg ATCC33277 [1.0×10³ and 1.0×10⁸ colony forming unit (CFU), respectively] 3 times per week for 8 weeks. In the sham group, 200 μl of phosphate buffer saline (PBS) was given instead. Behavioral tests: the navigation and the exploration tests using Morris water maze (MWM) were applied to evaluate learning and memory ability of rats. Immunohistochemistry was performed to detect cells positively expressing nestin, doublecortin (DCX) and neuronal nuclei (NeuN) in the subgranular zone (SGZ) of rats in each group. Western blotting was used to evaluate the expression levels of nestin, DCX and NeuN in rat hippocampus. Results: Learning and memory abilities: on day 5 of navigation test, the lagency time was 22.83 (16.00, 38.34) s in the high-intensity group, significantly longer than the sham group [5.59 (5.41, 6.17) s] (t=-11.17, P<0.001). There were no significant differences between the low-intensity group [9.85 (8.75, 21.01) s] and the sham group (t=-6.83, P=0.080). Results in the exploration test showed that, in the high-intensity group, the number of fime crossing over the previous platform area within 60 s was 1.50 (1.00, 2.00), significantly less than the sham group [4.00 (2.75, 4.00)] (t=9.75, P=0.003); no significant differences between the low-intensity group [2.50 (2.00, 3.00)] and the sham one (t=4.50, P=0.382). Immunohistochemistry showed that the nestin⁺ cell density in the low-intensity group [(35.36±4.32) cell/mm²] and high-intensity group [(26.51±5.89) cell/mm²] were significantly lower than the sham group [(59.58±14.15) cell/mm²] (t=24.21, P=0.018; t=33.07, P=0.005); as for the mean absorbance of DCX⁺ cells, the low-intensity group (0.007±0.002) and the high-intensity group (0.006±0.002) were significantly lower than the sham group (0.011±0.001) (t=0.004, P=0.018; t=0.006, P=0.005); compared with the sham group [(1.13±0.14)×10³ cell/mm²], the density of NeuN⁺ neurons in the high-intensity group [(0.75±0.08)×10³ cell/mm²] was significantly reduced (t=0.38, P=0.017), and was not significantly changed in the low-intensity group [(0.88±0.19)×10³ cell/mm²] (t=0.25, P=0.075). Western blotting results showed that, compared with the sham group, the expression levels of nestin, DCX, and NeuN were significantly reduced in the high-intensity group (t=0.74, P<0.001; t=0.18, P=0.014; t=0.35, P=0.008), but were not statistically changed in the low-intensity group (t=0.18, P=0.108; t=0.08, P=0.172; t=0.19, P=0.077). Conclusions: Pg injected through tail vein may reduce learning and memory abilities of wild-type rats, and may reduce the number of nestin, DCX, and NeuN-positive cells, and the protein expression levels of the above molecules in the hippocampus.

An individual sandwich hybrid nanostructure of cobalt disulfide in-situ grown on N doped carbon layer wrapped on multi-walled carbon nanotubes for high-efficiency lithium sulfur batteries

Binding and trapping of lithium polysulfide (LPS) are being conceived as the most effective strategies to improve lithium-sulfur (Li-S) battery performance. Therefore, exploiting a simple but cost-effective approach for the absorption and conversion of LPS and the transfer of electrons and Li⁺ ions is of paramount importance. Herein, sandwich structure MWCNTs@N-doped-C@CoS₂ integrated with multiple nanostructures of zero-dimensional (0D) CoS₂ nanoparticles, 1D carbon nanotubes (CNTs), and 2D N-doped amorphous carbon layer was obtained, where MWCNTs was firstly uniformly attached with a polydopamine (PDA) of excellent adhesion, followed by hydrothermal method, the Co²⁺ nanoparticles were in-situ grown on the PDA by the formation of complex compound of Co²⁺ and N atoms in PDA, and then the CoS₂ nanoparticles were in-situ grown on CNTs in a point-surface contact way by a bridging of N-doped amorphous carbon layer derived from the carbonization of attached PDA after the vulcanization at 500 °C under Ar atmosphere. The multifunction synergism of absorption, conductivity, and the kinetics of LPS redox is significantly improved, consequently effectively suppressing the shuttle effect and tremendously increasing the utilization rate of active substance. For the Li-S battery assembled with MWCNTs@N-doped-C@CoS₂-modified separator, its rate capacity and cycling performance can be greatly enhanced. It can exhibit a high initial discharge capacity of 1590 mAh g^-1 at 0.1 C, a stable long-term cycling performance with a relatively low capacity decay of 0.07% per cycle during 500 cycles at 1 C, and a reversible capacity of 772 mAh g^-1 and a capacity decay of 0.04% per cycle during 250 cycles at 2 C. Even at a large current density of 4 C, an initial specific discharge capacity of 634 mAh g^-1 can still be delivered. With a high sulfur loading of 5.0 mg cm^-2, additionally, an outstanding cycling stability can also be well maintained at 685 mAh g^-1 at 0.1 C after 50 cycles. This work provides a novel and simple but effective strategy to develop such sandwich hybrid materials comprised of polar metal sulfides and conductive networks via an effective bridging to help realize durable and stable Li-S battery.

[Peripheral blood EMR3 gene methylation level is correlated with breast cancer in Chinese women]

OBJECTIVE

To explore the association of methylation levels of C19orf57, MAP9, EMR3, NEK6 and PCOLCE2 genes in peripheral blood with breast cancer (BC) in Chinese women.

METHODS

We collected peripheral blood samples from 258 early-stage BC patients and 272 healthy women. Agena matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was utilized to quantitatively measure the methylation levels of CpG sites in the genes. The association between DNA methylation and BC was analyzed using a logistic regression model adjusted for covariants. Spearman's correlation analysis was performed to analyze the association between the gene methylation levels and age. The methylation levels of the genes in the BC patients with different clinical characteristics were investigated using non-parametric tests.

RESULTS

In stead of EMR3 gene hypermethylation as found in BC patients as found in the Caucasian population, EMR3 gene hypomethylation was found to correlate with BC in Chinese women, but this correlation was significant only in women beyond the age of 50 years (for every 10% reduction of the methylation level, EMR3_CpG_1: OR=1.40; EMR3_CpG_2: OR=2.31; EMR3_CpG_3: OR=2.76, P < 0.05). EMR3 methylation was not or was only weakly correlated with tumor stage, size, lymphatic metastasis, ER, PR, HER2, or Ki67. Our data did not show a correlation between C19orf57 methylation and BC.

CONCLUSION

Peripheral blood EMR3 gene hypomethylation is associated with BC in Chinese women, especially in those at an old age and in postmenopausal women.

A review about industrialization of Chinese materia medica decoction pieces

Chinese materia medica decoction pieces (CMMDPs), one of the three pillars of the Chinese materia medica industry, are a key link in the Chinese materia medica industrial chain. Industrialization is the only way for the modernization of CMMDPs. This review mainly summarizes the characteristics, history, current situation and prospect of CMMDPs industry, providing a new reference for promoting the flourishing development of the industrialization of CMMDPs and for serving massive health industry. The literature was collected from databases including Web of Science, PubMed, Elsevier and CNKI (Chinese). CMMDPs industry has the characteristics of regionalism, resource dependency, customer diversity and low industrial concentration. Deeply processed products include traditional Chinese medicine (TCM) formula granules, small-packed decoction pieces, ultrafine decoction pieces, puffed decoction pieces, compressed decoction pieces and instant decoction pieces. Integration of treatment and processing at the place of origin is emerging. However, there is still room for improvement, for example, the manufacturing technologies of CMMDPs industry need to be continually improved. The management of CMMDPs' normalized production also needs to be strengthened. The quality of CMMDPs should be strengthened supervision and it should establish the objective and feasible quality evaluation system for CMMDPs. At present, China has attached unprecedented importance to the development of TCM, and issued a number of supporting policies, sparing no effort to support its development.

[Survey on present status of noise exposure of workers in metal processing industry]

Objective: To investigate the distribution of noise exposure between non-steady state noise and steady-state noise for metal processing workers, which will provide scientific basis for the prevention and treatment of noise hazards in metal processing industry. Methods: The cross-section method was used to investigate the noise exposure of 737 workers from three metal processing industries in Zhejiang Province from October to December 2017. The general demographic information and occupational history were collected by questionnaire. The noise was recorded by individual noise meters, and the noise exposure intensity (equivalent continuous A-weighted noise exposure level normalized to an 8 h-working-day, L(Aeq, 8 h)) and kurtosis were calculated. Results: Workers exposed to noise in the metal processing industry were mainly 18-40 years old (527 workers, 71.51%) , men (570 workers, 77.34%) , and junior high school education background (416 workers, 56.45%) . There were 572 workers (77.61%) with noise exposure intensity (L(Aeq, 8 h)) greater than 85 dB (A) , 558 workers (75.71%) exposed to non-steady state noise (kurtosis ≥4) , and 634 workers (86.02%) with exposure duration less than 8 years. Among the 30 work types investigated, the work types with noise intensity reaching 100% were the stamping, welding and others from a children's car manufacturing factory in Ningbo, operating, chamfering, tapping, and thread rolling from an automobile parts manufacturing factory in Ningbo; The work types with a rate of 100% exposed to non-steady state noise were the grinding from a children's car manufacturing factory in Ningbo, assembling, assembly operating and others from an automobile brake manufacturing factory in Wenzhou, and polishing from an automobile parts manufacturing factory in Ningbo. Conclusion: Metal processing workers have a high rate of over-standard exposed to high noise intensity and a high proportion exposed to non-steady state noise. It is necessary to take sound insulation and noise reduction engineering control, and strengthen personal protection and occupational health management measures to prevent and control the noise hazards.

[Communication sound recognition and response modification in the secondary auditory cortex of female mice]

OBJECTIVE

To study the response characteristics of the secondary auditory cortex (A2) to wriggling calls (WC) and the mechanism of response modulation in female mice.

METHODS

We used patch-clamp and immunofluorescence labeling technique to mark and record the action potential and cell type of A2 neurons. Female C57 mice were stimulated with pure tone and white noise (control), 4.5 kHz, 9 kHz, or 13.5 kHz sound waves extracted from WC (single-frequency simulation group), the combinations of every two of the 3 single-frequency sound waves (two-tone frequency simulation group), or the combinations of 4.5 kHz+7.7 kHz+13.5 kHz and 4.5 kHz+9 kHz+13.5 kHz sound waves (three-frequency simulation group). The firing pattern, firing number, threshold, and latency of the action potential of the A2 neurons were recorded in response to the stimulations.

RESULTS

By comparison of the spikes elicited by different sound stimulations, we identified 3 types of neurons with different sensitivities to WC. The WC-sensitive neurons had a significantly greater number of spikes in response to WC than to other sounds and noise (P < 0.001). Comparison of the latency and threshold revealed significantly longer latencies of the WC-sensitive neurons and WC-insensitive neurons in response to WC stimulation than to pure tone stimulation (P=0.002), but their latencies to WC and noise stimulation were similar (P=0.093). The WC-sensitive neurons also had lower threshold to WC than to pure tone and noise stimulations (P=0.02). Analysis of the firing patterns of action potentials showed that the WCsensitive neurons consisted mainly of parvalbumin interneurons. The results of immunofluorescence labeling indicated that inhibitory interneurons were present in the A2 neurons that responded to WC.

CONCLUSION

A2 contains 3 types of neurons with different sensitivities to WC. Among them, the WC-sensitive neurons is mainly PV neurons, whose response characteristics to different types of sounds can help to explain the mechanism of communication sound recognition and response modification in A2.

Giant Piezoresistive Effect of CdS@C Hybrid Nanobelts for Volatile Real-Time Sensor and Erasable Nonvolatile Memory to Stress

Here, CdS@C nanohybrid composites, where CdS quantum dots (QDs) are uniformly embedded in carbon micro-/nanobelt matrixes, are synthesized via a combustion synthesis followed by a postvulcanization. In the nanohybrids, trap centers are effectively created by the introduction of QDs and moreover their barrier height and filling level can be effectively modulated through a coupling of externally loaded strain and bias. Thus, a single CdS@C micro-/nanobelt-based two-terminal device can exhibit an ultrahigh real-time response to compressive and tensile strains with a tremendous gauge factor of above 10⁴, high sensitivity, and fast response and recovery. More importantly, the trapped charges can be mechanically excited by stress, and furthermore, the stress-triggered high-resistance state can be well-maintained at room temperature and a relatively low operation bias. However, it can be back to its initial low resistance state by loading a relatively large bias, showing a superior erasable stress memory function with a window of about 10³. By an effective construction of trap centers in hybrid composites, not only can an ultrahigh performance of volatile real-time stress sensor be obtained under the synergism of external stress and electric field but also can an outstanding erasable nonvolatile stress memory be successfully realized.

Histology-based profile of inflammatory mediators in experimentally induced pulpitis in a rat model: screening for possible biomarkers

Aim

To profile molecular changes in lipopolysaccharide (LPS)‐induced experimental pulpitis in a rat model and explore the feasibility of a molecular‐based diagnostic strategy for pulpitis.

Methodology

Seventy‐three maxillary incisors of Sprague‐Dawley rats were used to establish pulpitis models with LPS. Inflammatory grading was performed in four equal sections of the pulp divided from the injured site to the root apex. An antibody array was used to compare the expression of 67 molecules between control pulp and inflamed pulp 12 and 72 h after LPS application. The levels of differentially expressed molecules in the control and inflamed pulp (collected at 3, 6, 9, 12, 24 and 72 h after LPS treatment) were examined via ELISA, and correlations between inflammatory scores and molecule expression were assessed. The molecule distributions in the pulp were investigated by immunofluorescence staining. Data were analysed with paired t‐test, one‐way anova, Kruskal–Wallis tests, and Spearman’s and Pearson’s correlations with significance set at P < 0.05.

Results

Polymorphonuclear neutrophils were observed in the injured site 3 h after LPS stimulation. Inflammatory infiltration peaked at 12 h and was limited to the injured site with osteodentine deposition at 72 h. Thirteen molecules were significantly differentially expressed between the control and LPS‐injured pulp. ELISA validated that tissue inhibitor of metalloproteinase‐1 (TIMP‐1) expression dramatically peaked at 12 h (compared with other time points, P < 0.05) and returned to baseline at 72 h. The TIMP‐1 concentration was strongly correlated with inflammation severity in the apical three‐quarters of the pulp, and the strongest correlation was found in the lower‐middle quarter (r = 0.786, P < 0.001). Immunofluorescence staining revealed that in the apical three‐quarters of the pulp, TIMP‐1 expression was significantly higher in the 12 h group than in the control and 3, 6, 24 and 72 h groups (P < 0.01).

Conclusion

This study provides a molecular profile of LPS‐induced pulpitis in a rat model. TIMP‐1 had a strong positive correlation with the severity of dental pulp inflammation, verifying the feasibility of applying biomarkers to identify specific pathological conditions in pulpitis.

[An analysis of insomnia and its influencing factors in patients with acute coronary syndrome]

Objective: To investigate the current situation of insomnia in patients with acute coronary syndrome (ACS), and analyze the influencing factors of insomnia in the ACS patients, so as to provide information on the development of new strategies for the treatment of insomnia in ACS patients. Methods: This is a multicenter and prospective observational study. A total of 771 ACS patients who met the criteria were selected from March 2013 to June 2015. The baseline social demographic information, sleep quality questionnaire, general anxiety disorder scale-7(GAD-7),patient health questionnaire-9(PHQ-9), short-form 12 health survey questionnaire(SF-12), and enhancing recovery in coronary heart disease patients social inventory(ESSI) were completed within 7 days after admission. Logistic regression analyses were used to analyze the influencing factors of insomnia in ACS patients. Results: A total of 741 subjects with valid questionnaires were collected, including 510 males (68.8%) and 231 females (31.2%). Among them, 487 (65.7%) subjects had at least one insomnia symptom: 308 (41.6%) subjects had difficulty in falling asleep, 369 (49.8%) subjects were easy to wake at night, 116 (15.7%) subjects woke up earlier than they expected, 74 (10.0%) subjects experienced both woke up earlier and difficulty in falling asleep, and 53 (7.2%) subjects woke up earlier, woke up at night and had difficulty in falling asleep at the same time. Logistic regression analyses showed that before admission physical activity (OR =0.636, 95%CI 0.411-0.984), depression (OR=1.908, 95%CI 1.101-3.305) and low social support (OR=0.278, 95%CI 1.198-3.301) were independent factors of insomnia in ACS patients. Conclusions: Nearly 2/3 ACS patients have symptoms of insomnia. Difficulty in falling asleep and easy to wake up at night are the most common manifestations. Physical activity, depression and social support independently are associated with insomnia.

Bi19S27I3 nanorods: a new candidate for photothermal therapy in the first and second biological near-infrared windows

Near-infrared (NIR) light-induced photothermal cancer therapy using nanomaterials as photothermal agents has attracted considerable research interest over the past few years. As the key factor in photothermal therapy systems, a variety of photothermal agents have been developed. However, the exploration of novel photothermal therapy nanoplatforms with high NIR absorption remains a significant challenge, especially those working in both NIR-I and NIR-II windows. In this work, Bi19S27I3 nanorods with remarkably high absorption covering the whole visible light to the entire NIR-I and NIR-II regions have been successfully prepared through a facile solvothermal approach. The as-synthesized Bi19S27I3 nanorods have a high photothermal conversion efficiency of 42.7% at 808 nm (NIR-I) and 41.5% at 1064 nm (NIR-II), making them a promising candidate for photothermal therapy. In vitro cell viability assay reveals that the Bi19S27I3 sample has good biocompatibility and exhibits significant cell-killing effect under NIR irradiation. In vivo anti-tumor experiments demonstrate that the tumor growth can be effectively inhibited by fatal hyperthermia ablation mediated by Bi19S27I3 nanorods under the irradiation of an 808 nm or 1064 nm laser. Therefore, this study should be primarily beneficial for the development of new materials for NIR photothermal therapy applications.

Timing of paediatric orchidopexy in universal healthcare systems: international administrative data cohort study

BACKGROUND

International guidelines in 2008 recommended orchidopexy for undescended testis at 6-12 months of age to reduce the risk of testicular cancer and infertility. Using administrative data from England, Finland, Ontario (Canada), Scotland and Sweden (with data from Victoria (Australia) and Iceland in supplementary analyses), the aim of this study was to investigate compliance with these guidelines and identify potential socioeconomic inequities in the timing of surgery before 1 and 3 years.

METHODS

All boys born in 2003-2011 with a diagnosis code of undescended testis and procedure codes indicating orchidopexy before their fifth birthday were identified from administrative health records. Trends in the proportion of orchidopexies performed before 1 and 3 years of age were investigated, as were socioeconomic inequities in adherence to the guidelines.

RESULTS

Across all jurisdictions, the proportion of orchidopexies occurring before the first birthday increased over the study period. By 2011, from 7·6 per cent (Sweden) to 27·9 per cent (Scotland) of boys had undergone orchidopexy by their first birthday and 71·5 per cent (Sweden) to 90·4 per cent (Scotland) by 3 years of age. There was limited evidence of socioeconomic inequities for orchidopexy before the introduction of guidelines (2008). Across all jurisdictions for boys born after 2008, there was consistent evidence of inequities in orchidopexy by the first birthday, favouring higher socioeconomic position. Absolute differences in these proportions between the highest and lowest socioeconomic groups ranged from 2·5 to 5·9 per cent across jurisdictions.

CONCLUSION

Consistent lack of adherence to the guidelines across jurisdictions questions whether the guidelines are appropriate.

Photoflexoelectric effect in halide perovskites

Harvesting environmental energy to generate electricity is a key scientific and technological endeavour of our time. Photovoltaic conversion and electromechanical transduction are two common energy-harvesting mechanisms based on, respectively, semiconducting junctions and piezoelectric insulators. However, the different material families on which these transduction phenomena are based complicate their integration into single devices. Here we demonstrate that halide perovskites, a family of highly efficient photovoltaic materials^1-3, display a photoflexoelectric effect whereby, under a combination of illumination and oscillation driven by a piezoelectric actuator, they generate orders of magnitude higher flexoelectricity than in the dark. We also show that photoflexoelectricity is not exclusive to halides but a general property of semiconductors that potentially enables simultaneous electromechanical and photovoltaic transduction and harvesting in unison from multiple energy inputs.

Wurtzite CuNi2InS4 Nanocrystals: A Quaternary Chalcogenide Magnetic Semiconductor

For the first time, quaternary chalcogenide CuNi₂InS₄ nanocrystals with a wurtzite structure have been designed and fabricated as a new magnetic semiconductor. The phase structure analysis suggests that the synthesized wurtzite CuNi₂InS₄ phase has a disordered structure in which Cu⁺, Ni²⁺, and In³⁺ ions share the same lattice site of the unit cell with a random cation distribution. The prepared CuNi₂InS₄ nanocrystals have uniform bullet-like morphology, small size distribution, good monodispersity, and high crystallinity. The magnetic properties investigation reveals that the wurtzite CuNi₂InS₄ nanocrystals can exhibit a weak ferromagnetic moment with the blocking temperature at around 13 K thanks to the disordered wurtzite structure and the high content of magnetic Ni²⁺ ions. As for the semiconducting properties, the as-obtained wurtzite CuNi₂InS₄ nanocrystals show a strong and broad visible light absorption and have a direct bandgap of 1.45 eV. Due to their favorable optical properties, the fabricated thin film of CuNi₂InS₄ nanocrystals exhibits a good photoelectric response to the solar spectrum, which makes the obtained new phase potential candidate for applications in the photovoltaics. This work demonstrates a new metastable I-II₂-III-VI₄ chalcogenide that can be used to render multiple functionalities and applications.

Bias-Controlled Tunable Electronic Transport with Memory Characteristics in an Individual ZnO Nanowire for Realization of a Self-Driven UV Photodetector with Two Symmetrical Electrodes

ZnO nanostructures are exceedingly important building blocks for nanodevices due to their wide band gap and large exciton binding energy. However, their electronic transport characteristics are unstable and unrepeatable with external environment variation. Here, we demonstrate that electron transport of an individual ZnO nanowire-based device with the two same electrodes can be controllably modulated by applying a relatively large uni-/bidirectional bias. After being modulated, moreover, their electrical properties can well be maintained at relatively low operation bias and room temperature, demonstrating a memory behavior. The presence of surface states related to lattice periodicity breaking and traps associated with oxygen vacancy (V_o) and zinc interstitial (Zn_i) deep-level defects plays a crucial role in tunable electron transport with a memory feature. For the single nanowire-based two-terminal device, two back-to-back connected surface barrier diodes with series resistance are formed. The filling and emptying of traps near two end electrodes can remarkably adjust the width and height of the surface barrier. At a relatively low bias, the unmodulated conductance is governed by the electron hopping of bulk traps since the height of emptied traps is higher than that of the surface barrier, whereas at a relatively large bias, it is dominated by thermion emission due to a dramatic decrease of the surface barrier width resulting from the electron injection into traps from a negative electrode. Moreover, it will be beneficial for a thin surface barrier to penetrate UV light and separate photoexcited electron-hole pairs. After being asymmetrically modulated by a unidirectional injection, it can be successfully applied to realize a self-driven UV photodetector based on a photovoltaic effect in the symmetrical two-electrode structure. Our work provides a new route to tune electrical properties of nanostructures, which may inspire the development of novel electronic and optoelectronic devices.

Positive- and negative-tone structuring of crystalline silicon by laser-assisted chemical etching

We demonstrate a structuring method for crystalline silicon using nanosecond laser internal irradiation followed by chemical etching. We show a dramatic dependence of the etch rate on the laser-writing speed. Enhanced isotropic etch rates of silicon by laser-induced internal damage were recently demonstrated with strong acids, but our results add the possibility to obtain reduced etch rates leading to different topographies. Material analyses indicate the possibility to efficiently produce high-aspect ratio channels, thanks to laser-induced porosities, as well as silicon micro-bumps due to highly stressed regions. This holds promises for fabricating microfluidic, photovoltaic, and micro-electromechanical systems.

Optical creation of a supercrystal with three-dimensional nanoscale periodicity

Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO₃/SrTiO₃ superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states.