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Abstract Background Macrophage activation syndrome is a rare disorder leading to unregulated immune activity manifesting with nonspecific constitutional symptoms, laboratory abnormalities, and multiorgan involvement. We report the case of a patient who presented with acute hepatitis secondary to macrophage activation syndrome diagnosed by liver biopsy and successfully treated with intravenous immune globulin, anakinra, and rituximab. Case presentation A 42-year-old Laotian woman with adult-onset immunodeficiency with anti-interferon gamma antibodies presented with a fever, headache, generalized myalgia, dark urine, and reduced appetite in the setting of family members at home with similar symptoms. Her laboratory workup was notable for evidence of acute hepatitis without acute liver failure. After an unrevealing comprehensive infectious and noninvasive rheumatologic workup was completed, a liver biopsy was performed ultimately revealing the diagnosis of macrophage activation syndrome. She was successfully treated with intravenous immune globulin, anakinra, and rituximab. Conclusion This case highlights the importance of maintaining macrophage activation syndrome on the differential of a patient with acute hepatitis of unknown etiology in the correct clinical context and the value of a liver biopsy in making a diagnosis when noninvasive testing is unrevealing.

Abstract Reliable and available non-invasive methods for hepatic fibrosis assessment are important in chronic liver disease (CLD). Our aim was to compare stepwise algorithms combining standard ultrasound with serum markers and transient elastography (TE) for detecting advanced fibrosis (F3-4) and cirrhosis. Retrospective single center study between 2012 and 2018 of CLD patients with biopsy, TE, blood tests, and liver ultrasound parameters of surface nodularity (SN), lobar redistribution, and hepatic vein nodularity. Our cohort included 157 patients (51.6% males), mean age 47.6 years, predominantly non-alcoholic fatty liver disease and viral hepatitis (61%), with F3-4 prevalence of 60.5%. Area under the curve for F3-4 was 0.89 for TE ≥ 9.6 kPa and 0.80 for FIB-4 > 3.25. In multivariate modeling, TE ≥ 9.6 kPa (OR 21.78) and SN (OR 3.81) had independent association with F3-4; SN (OR 5.89) and TE ≥ 10.2 kPa (OR 15.73) were independently associated with cirrhosis. Two stepwise approaches included FIB-4 followed by SN or TE; sensitivity and specificity of stepwise SN were 0.65 and 1.00, and 0.89 and 0.33 for TE ≥ 9.6 kPa, respectively. Ultrasound SN and TE were independently predictive of F3-4 and cirrhosis in our cohort. FIB-4 followed by SN had high specificity for F3-4.

Background. Since October 2021, there have been more than 500 cases of severe hepatitis of unknown origin in children reported worldwide, including 180 cases in the U.S. The most frequently detected potential pathogen to date has been adenovirus, typically serotype 41. Adenovirus is known to cause a self-limited infection in the immunocompetent host. However, in immunosuppressed individuals, severe or disseminated infections may occur. Method. We present the case of a two-year-old female who presented with cholestatic hepatitis and acute liver failure (ALF). Work up for etiologies of ALF was significant for adenovirus viremia, but liver biopsy was consistently negative for the virus. The risk for severe adenoviral infection in the setting of anticipated immunosuppression prompted us to initiate cidofovir to decrease viral load prior to undergoing liver transplantation. Result. Our patient received a successful liver transplant, cleared the viremia after 5 doses of cidofovir, and continues to maintain allograft function without signs of infection at the time of this report, 5 months posttransplant. Conclusion. Recent reports of pediatric hepatitis cases may be associated with adenoviral infection although the exact relationship is unclear. There is the possibility of the ongoing SARS-CoV-2 environment, or other immunologic modifying factors. All patients presenting with hepatitis or acute liver failure should be screened for adenovirus and reported to state health departments. Cidofovir may be used to decrease viral load prior to liver transplantation, to decrease risk of severe adenoviral infection.

Objective: Non-alcoholic fatty liver disease (NAFLD) covers a wide spectrum of liver pathology ranging from simple fatty liver to non-alcoholic steatohepatitis (NASH). Notably, immune cell-driven inflammation is a key mechanism in the transition from fatty liver to the more serious NASH. Although exercise training is effective in ameliorating obesity-related diseases, the underlying mechanisms of the beneficial effects of exercise remain unclear. It is unknown whether there is an optimal modality and intensity of exercise to treat NAFLD. The objective of this study was to determine whether high-intensity interval training (HIIT) or moderate-intensity continuous training (MIT) is more effective at ameliorating the progression of NASH. Methods: Wild-type mice were fed a high-fat, high-carbohydrate (HFHC) diet for 6 weeks and left sedentary (SED) or assigned to either an MIT or HIIT regimen using treadmill running for an additional 16 weeks. MIT and HIIT groups were pair-fed to ensure that energy intake was similar between the exercise cohorts. To determine changes in whole-body metabolism, we performed insulin and glucose tolerance tests, indirect calorimetry, and magnetic resonance imaging. NASH progression was determined by triglyceride accumulation, expression of inflammatory genes, and histological assessment of fibrosis. Immune cell populations in the liver were characterized by cytometry by time-of-flight mass spectrometry, and progenitor populations within the bone marrow were assessed by flow cytometry. Finally, we analyzed the transcriptional profile of the liver by bulk RNA sequencing. Results: Compared with SED mice, both HIIT and MIT suppressed weight gain, improved whole-body metabolic parameters, and ameliorated the progression of NASH by reducing hepatic triglyceride levels, inflammation, and fibrosis. However, HIIT was superior to MIT at reducing adiposity, improving whole-body glucose tolerance, and ameliorating liver steatosis, inflammation, and fibrosis, without any changes in body weight. Improved NASH progression in HIIT mice was accompanied by a substantial decrease in the frequency of pro-inflammatory infiltrating, monocyte-derived macrophages in the liver and reduced myeloid progenitor populations in the bone marrow. Notably, an acute bout of MIT or HIIT exercise had no effect on the intrahepatic and splenic immune cell populations. In addition, bulk mRNA sequencing of the entire liver tissue showed a pattern of gene expression confirming that HIIT was more effective than MIT in improving liver inflammation and lipid biosynthesis. Conclusions: Our data suggest that exercise lessens hepatic inflammation during NASH by reducing the accumulation of hepatic monocyte-derived inflammatory macrophages and bone marrow precursor cells. Our findings also indicate that HIIT is superior to MIT in ameliorating the disease in a dietary mouse model of NASH.

BackgroundHepatocellular Carcinoma (HCC) is a sexually dimorphic cancer, with female sex being independently protective against HCC incidence and progression. The aim of our study was to understand the mechanism of estrogen receptor signaling in driving sex differences in hepatocarcinogenesis.MethodsWe integrated 1,268 HCC patient sample profiles from publicly available gene expression data to identify the most differentially expressed genes (DEGs). We mapped DEGs into a physical protein interaction network and performed network topology analysis to identify the most important proteins. Experimental validation was performed in vitro on HCC cell lines, in and in vivo, using HCC mouse model.ResultsWe showed that the most central protein, ESR1, is HCC prognostic, as increased ESR1 expression was protective for overall survival, with HR=0.45 (95%CI 0.32-0.64, p=4.4E-06), and was more pronounced in women. Transfection of HCC cell lines with ESR1 and exposure to estradiol affected expression of genes involved in the Wnt/β-catenin signaling pathway. ER-α (protein product of ESR1) agonist treatment in a mouse model of HCC resulted in significantly longer survival and decreased tumor burden (p

Systemic lupus erythematosus (SLE) is an autoimmune connective tissue disease, characterized by autoantibody production and immune complex formation, that has the potential to affect virtually any organ. Pleuropulmonary involvement occurs in 50–70% and commonly manifests as pleuritis and pleural effusion. Diffuse alveolar hemorrhage (DAH) is a rare manifestation of SLE. Most cases of DAH occur in young adults with an underlying autoimmune disease such as systemic vasculitis or Goodpasture syndrome. SLE is typically lower on the list of initial differential diagnoses of DAH due to its rarity compared to other etiologies. We present a case of a patient with dyspnea on exertion, dry coughs, lower extremity edema, and intermittent periorbital edema who ultimately succumbed to respiratory failure secondary to DAH in the setting of SLE. The diagnosis of SLE was suspected clinically and confirmed at autopsy due to her rapid clinical deterioration. DAH requires prompt intervention, and management is guided by the underlying disease process. SLE is a potentially treatable disease; therefore, timely diagnosis is important in order to exclude other noninfectious causes of DAH (reviewed in this report) and to initiate appropriate therapy.

The development of single cell RNA sequencing technologies has been instrumental in advancing our understanding of tissue biology. Here, MacParland et al. performed single cell RNA sequencing of human liver samples, and identify distinct populations of intrahepatic macrophages that may play specific roles in liver disease.

Mounting effective innate and adaptive immune responses are critical for viral clearance and the generation of long lasting immunity. It is known that production of inhibitory factors may result in the inability of the host to clear viruses, resulting in chronic viral persistence. Fibrinogen-like protein 2 (FGL2) has been identified as a novel effector molecule of CD4(+)CD25(+) Foxp3(+) regulatory T (Treg) cells that inhibits immune activity by binding to FCγRIIB expressed primarily on antigen presenting cells (APC). In this study, we show that infection of mice with Lymphocytic Choriomeningitis Virus WE (LCMV WE) leads to increased plasma levels of FGL2, which were detected as early as 2 days post-infection (pi) and persisted until day 50 pi. Mice deficient in FGL2 (fgl2(-/-)) had increased viral titers of LCMV WE in the liver early p.i but cleared the virus by day 12 similar to wild type mice. Dendritic cells (DC) isolated from the spleens of LCMV WE infected fgl2(-/-) had increased expression of the DC maturation markers CD80 and MHC Class II compared to wild type (fgl2(+/+)). Frequencies of CD8(+) and CD4(+) T cells producing IFNγ in response to ex vivo peptide re-stimulation isolated from the spleen and lymph nodes were also increased in LCMV WE infected fgl2(-/-) mice. Increased frequencies of CD8(+) T cells specific for LCMV tetramers GP33 and NP396 were detected within the liver of fgl2(-/-) mice. Plasma from fgl2(-/-) mice contained higher titers of total and neutralizing anti-LCMV antibody. Enhanced anti-viral immunity in fgl2(-/-) mice was associated with increased levels of serum alanine transaminase (ALT), hepatic necrosis and inflammation following LCMV WE infection. These data demonstrate that targeting FGL2 leads to early increased viral replication but enhanced anti-viral adaptive T & B cell responses. Targeting FGL2 may enhance the efficacy of current anti-viral therapies for hepatotropic viruses.

TCRαβ(+) CD4(-)CD8(-)NK(-) double negative T cells (DN T cells) can act as regulatory T cells to inhibit allograft rejection and autoimmunity. Their role in graft-versus-host disease and mechanisms of suppression remain elusive. In this study, we demonstrate that DN T cells can inhibit CD4(+) T cell-mediated GVHD in a semi-allogeneic model of bone marrow transplantation. Furthermore, we present evidence of a novel autocrine IFNγ signaling pathway in Fas-deficient C57BL/6.lpr (B6.lpr) DN T cells. B6.lpr DN T cells lacking IFNγ or its receptor were impaired in their ability to suppress syngeneic CD4(+) T cells responding to alloantigen stimulation both in vitro and in vivo. Autocrine IFNγ signaling was required for sustained B6.lpr DN T cell IFNγ secretion in vivo and for upregulation of surface Fas ligand expression during TCR stimulation. Fas ligand (FasL) expression by B6.lpr DN T cells permitted lysis of activated CD4(+) T cells and was required for suppression of GVHD. Collectively, our data indicate that DN T cells can inhibit GVHD and that IFNγ plays a critical autocrine role in controlling the regulatory function of B6.lpr DN T cells.

Xenografting primary human solid tumor tissue into immunodeficient mice is a widely used tool in studies of human cancer biology; however, care must be taken to prove that the tumors obtained recapitulate parent tissue. We xenografted primary human hepatocellular carcinoma (HCC) tumor fragments or bulk tumor cell suspensions into immunodeficient mice. We unexpectedly observed that 11 of 21 xenografts generated from 16 independent patient samples resembled lymphoid neoplasms rather than HCC. Immunohistochemistry and flow cytometry analyses revealed that the lymphoid neoplasms were comprised of cells expressing human CD45 and CD19/20, consistent with human B lymphocytes. In situ hybridization was strongly positive for Epstein-Barr virus (EBV) encoded RNA. Genomic analysis revealed unique monoclonal or oligoclonal immunoglobulin heavy chain gene rearrangements in each B-cell neoplasm. These data demonstrate that the lymphoid neoplasms were EBV-associated human B-cell lymphomas. Analogous to EBV-associated lymphoproliferative disorders in immunocompromised humans, the human lymphomas in these HCC xenografts likely developed from reactivation of latent EBV in intratumoral passenger B lymphocytes following their xenotransplantation into immunodeficient recipient mice. Given the high prevalence of latent EBV infection in humans and the universal presence of B lymphocytes in solid tumors, this potentially confounding process represents an important pitfall of human solid tumor xenografting. This phenomenon can be recognized and avoided by routine phenotyping of primary tumors and xenografts with human leukocyte markers, and provides a compelling biological rationale for exclusion of these cells from human solid tumor xenotransplantation assays.

The group-10 noble-metal dichalcogenides have recently emerged as a promising group of two-dimensional materials due to their unique crystal structures and fascinating physical properties. In this work, the resonance enhancement of the interlayer breathing mode (B1) and intralayer A g 1 and A g 3 modes in atomically thin pentagonal PdSe 2 were studied using angle-resolved polarized Raman spectroscopy with 13 excitation wavelengths. Under the excitation energies of 2.33, 2.38, and 2.41 eV, the Raman intensities of both the low-frequency breathing mode B1 and high-frequency mode A g 1 of all the thicknesses are the strongest when the incident polarization is parallel to the a axis of PdSe 2 , serving as a fast identification of the crystal orientation of few-layer PdSe 2 . We demonstrated that the intensities of B1, A g 1 , and A g 3 modes are the strongest with the excitation energies between 2.18 and 2.38 eV when the incident polarization is parallel to PdSe 2 a axis, which arises from the resonance enhancement caused by the absorption. Our investigation reveals the underlying interplay of the anisotropic electron-phonon and electron-photon interactions in the Raman scattering process of atomically thin PdSe 2 . It paves the way for future applications on PdSe 2 -based optoelectronics., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The role of additives in facilitating the growth of conventional semiconducting thin films is well-established. Apparently, their presence is also decisive in the growth of two-dimensional transition metal dichalcogenides (TMDs), yet their role remains ambiguous. In this work, we show that the use of sodium bromide enables synthesis of TMD monolayers via a surfactant-mediated growth mechanism, without introducing liquefaction of metal oxide precursors. We discovered that sodium ions provided by sodium bromide chemically passivate edges of growing molybdenum disulfide crystals, relaxing in-plane strains to suppress 3D islanding and promote monolayer growth. To exploit this growth model, molybdenum disulfide monolayers were directly grown into desired patterns using predeposited sodium bromide as a removable template. The surfactant-mediated growth not only extends the families of metal oxide precursors but also offers a way for lithography-free patterning of TMD monolayers on various surfaces to facilitate fabrication of atomically thin electronic devices.

We report atomically precise pentagonal PdSe 2 nanoribbons (PNRs) fabricated on a pristine PdSe 2 substrate with a hybrid method of top-down and bottom-up processes. The PNRs form a uniform array of dimer structure with a width of 2.4 nm and length of more than 200 nm. In situ four-probe scanning tunneling microscopy (STM) reveals metallic behavior of PNRs with ballistic transport for at least 20 nm in length. Density functional theory calculations produce a semiconducting density of states of isolated PNRs and find that the band gap narrows and disappears quickly once considering coupling between PNR stacking layers or interaction with the PdSe 2 substrate. The coupling of PNRs is further corroborated by Raman spectroscopy and field-effect transistor measurements. The facile method of fabricating atomically precise PNRs offers an air-stable functional material for dimensional control.

For the first time, a multi-centre Total Diet Study was carried out in Benin, Cameroon, Mali and Nigeria. We collected and prepared as consumed 528 typical fatty foods from those areas and pooled these subsamples into 44 composites samples. These core foods were tested for a wide spectrum of POPs, including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), brominated flame-retardants (BFRs), organochlorine compounds (OCs), perfluoro alkyl substances (PFAS) and chlorinated flame retardants (CFRs). The POPs contamination levels were similar or lower than those reported in total diet studies previously conducted worldwide. In most cases, core foods belonging to fish food group presented higher POPs concentrations than the other food groups. Interestingly, we observed a difference in both contamination profile and concentration for smoked fish compared to non-smoked fish. Such finding suggests that the smoking process itself might account for a large proportion of the contamination. Further investigation would require the assessment of combustion materials used to smoke fish as a potential vehicle, which may contribute to the dietary exposure of the studied populations to POPs., (Copyright © 2019 Food and Agriculture Organization of the United Nations. Published by Elsevier Ltd.. All rights reserved.)

This paper reports occurrence data related to 30 trace elements in food composite samples from a multi-regional Sub-Saharan Africa Total Diet Study. Herein, 2700 samples grouped in 225 food composite samples corresponding to 13 food groups: cereals, tubers, legumes, vegetables, fruits, nuts/seeds, meat, eggs, fish, milk/dairy, oil/fats, and beverages from eight locations in four countries, namely Benin (Littoral/Borgou), Cameroon (Duala/North), Mali (Bamako/Sikasso), and Nigeria (Lagos/Kano) were prepared as consumed, pooled, and analysed using a validated method based on inductively coupled plasma-mass spectrometry. The occurrence data for Al, As, Cd, Hg, and Pb as regulated by the Codex Alimentarius are discussed herein. Although the levels of As, Cd, Hg, and Pb were above the limit of quantification, they were below the maximum limits set by the Codex in most samples analysed. A distinct feature was observed for cereals and tubers, as they were mostly contaminated with Al and Pb. A pilot study regarding the impact of using artisanal cookware (made from recycled aluminium) on the contamination of food samples was performed. Relevant contamination with Al and Pb when cooking tomato samples from Cameroon and Nigeria using artisanal aluminium cookware was compared to that when cooked using stainless-steel., (Copyright © 2019 Food and Agriculture Organization of the United Nations. Published by Elsevier Ltd.. All rights reserved.)

The failure to achieve stable Ohmic contacts in two-dimensional material devices currently limits their promised performance and integration. Here we demonstrate that a phase transformation in a region of a layered semiconductor, PdSe 2 , can form a contiguous metallic Pd 17 Se 15 phase, leading to the formation of seamless Ohmic contacts for field-effect transistors. This phase transition is driven by defects created by exposure to an argon plasma. Cross-sectional scanning transmission electron microscopy is combined with theoretical calculations to elucidate how plasma-induced Se vacancies mediate the phase transformation. The resulting Pd 17 Se 15 phase is stable and shares the same native chemical bonds with the original PdSe 2 phase, thereby forming an atomically sharp Pd 17 Se 15 /PdSe 2 interface. These Pd 17 Se 15 contacts exhibit a low contact resistance of ∼0.75 kΩ μm and Schottky barrier height of ∼3.3 meV, enabling nearly a 20-fold increase of carrier mobility in PdSe 2 transistors compared to that of traditional Ti/Au contacts. This finding opens new possibilities in the development of better electrical contacts for practical applications of 2D materials.

In the framework of the first regional Total Diet Study in Sub-Saharan Africa, 3696 foodstuffs, commonly consumed in Benin, Cameroon, Mali and Nigeria were purchased, prepared as consumed and pooled into 308 composite samples. Those core foods were tested for up to 470 pesticides residues by liquid and gas chromatography coupled with tandem mass spectrometry. 39 pesticides were detected with 294 total occurrences, including 47.3% organophosphate pesticides and 35.7% pyrethroids. More specifically, 6 substances represented 75.5% of all 3 organophosphates and 3 pyrethroids: chlorpyrifos (22.4%) cypermethrin (18.0%) dichlorvos (13.6%), lambda cyhalothrin (8.2%), permethrin (7.5%) and profenofos (5.8%). One pesticide or more was detected in 45.8% of samples. Strikingly, several pesticides were quantified in 2 composite samples of smoked fish from Mali: chlorpyrifos (5236-18 084 μg/kg), profenofos (30-182 μg/kg), cypermethrin (22-250 μg/kg), cyfluthrin (16-117 μg/kg), lambda cyhalothrin (9-17 μg/kg) and permethrin (3-6 μg/kg)., Competing Interests: The authors declare that there is no conflict of interest.

In the framework of the first multi-centre Sub-Saharan Africa Total Diet Study (SSA-TDS), 2328 commonly consumed foods were purchased, prepared as consumed and pooled into 194 composite samples of cereals, tubers, legumes, vegetables, nuts and seeds, dairy, oils, beverages and miscellaneous. Those core foods were tested for mycotoxins and other fungal, bacterial and plant secondary metabolites by liquid chromatography, coupled with tandem mass spectrometry. The highest aflatoxin concentrations were quantified in peanuts, peanut oil and maize. The mean concentration of the sum of aflatoxins AFB1, AFB2, AFG1 and AFG2 (AF tot ) in peanut samples (56.4 µg/kg) exceeded EU (4 µg/kg) and Codex (15 µg/kg) standards. The AF tot concentration (max: 246.0 µg/kg) was associated with seasonal and geographic patterns and comprised, on average, 80% AFB1, the most potent aflatoxin. Although ochratoxin A concentrations rarely exceeded existing Codex standards, it was detected in unregulated foods. One palm oil composite sample contained 98 different metabolites, including 35.4 µg/kg of ochratoxin A. In total, 164 different metabolites were detected, with unspecific metabolites like asperglaucide, cyclo(L-pro-L-val), cyclo (L-pro-L-tyr), flavoglaucin, emodin and tryptophol occurring in more than 50% of composite samples. Aflatoxin B1 (AFB1), fumonisin B1 (FB1), sterigmatocystin (STC), ochratoxin A (OTA), citrinin (CIT) and many other secondary fungal metabolites are frequent co-contaminants in staple foods, such as maize and sorghum. Populations from North Cameroon and from Benin may, therefore, suffer chronic and simultaneous exposure to AFB1, FB1, STC, OTA and CIT, which are prevalent in their diet., Competing Interests: The authors declare that there is no conflict of interest.

Atmospheric and long-term aging effects on electrical properties of WSe 2 transistors with various thicknesses are examined. Although countless published studies report electrical properties of transition-metal dichalcogenide materials, many are not attentive to testing environment or to age of samples, which we have found significantly impacts results. Our as-fabricated exfoliated WSe 2 pristine devices are predominantly n-type, which is attributed to selenium vacancies. Transfer characteristics of as-fabricated devices measured in air then vacuum reveal physisorbed atmospheric molecules significantly reduced n-type conduction in air. First-principles calculations suggest this short-term reversible atmospheric effect can be attributed primarily to physisorbed H 2 O on pristine WSe 2 , which is easily removed from the pristine surface in vacuum due to the low adsorption energy. Devices aged in air for over 300 h demonstrate irreversibly increased p-type conduction and decreased n-type conduction. Additionally, they develop an extended time constant for recovery of the atmospheric adsorbents effect. Short-term atmospheric aging (up to approximately 900 h) is attributed to O 2 and H 2 O molecules physisorbed to selenium vacancies where electron transfer from the bulk and adsorbed binding energies are higher than the H 2 O-pristine WSe 2 . The residual/permanent aging component is attributed to electron trapping molecular O 2 and isoelectronic O chemisorption at selenium vacancies, which also passivates the near-conduction band gap state, p-doping the material, with very high binding energy. All effects demonstrated have the expected thickness dependence, namely, thinner devices are more sensitive to atmospheric and long-term aging effects.

Two-dimensional materials such as layered transition-metal dichalcogenides (TMDs) are ideal platforms for studying defect behaviors, an essential step towards defect engineering for novel material functions. Here, we image the 3D lattice locations of selenium-vacancy V_{Se} defects and manipulate them using a scanning tunneling microscope (STM) near the surface of PdSe_{2}, a recently discovered pentagonal layered TMD. The V_{Se} show a characterisitc charging ring in a spatially resolved conductance map, based on which we can determine its subsurface lattice location precisely. Using the STM tip, not only can we reversibly switch the defect states between charge neutral and charge negative, but also trigger migrations of V_{Se} defects. This allows a demonstration of direct "writing" and "erasing" of atomic defects and tracing the diffusion pathways. First-principles calculations reveal a small diffusion barrier of V_{Se} in PdSe_{2}, which is much lower than S vacancy in MoS_{2} or an O vacancy in TiO_{2}. This finding opens an opportunity of defect engineering in PdSe_{2} for such as controlled phase transformations and resistive-switching memory device application.

In-plane heterojuctions formed from two monolayer semiconductors represent the finest control of electrons in condensed matter and have attracted significant interest. Various device studies have shown the effectiveness of such structures to control electronic processes, illustrating their potentials for electronic and optoelectronic applications. However, information about the physical mechanisms of charge carrier transfer across the junctions is still rare, mainly due to the lack of adequate experimental techniques. Here we show that transient absorption measurements with high spatial and temporal resolution can be used to directly monitor such transfer processes. We studied MoS 2 -MoSe 2 in-plane heterostructures fabricated by chemical vapor deposition and lithographic patterning followed by laser-generated vapor sulfurization. Transient absorption measurements in reflection geometry revealed evidence of exciton transfer from MoS 2 to MoSe 2 . By comparing the experimental data with a simulation, we extracted an exciton transfer velocity of 10 4 m s -1 . These results provide valuable information for understanding and controlling in-plane carrier transfer in two-dimensional lateral heterostructures for their electronic and optoelectronic applications.

The formation of an electric double layer in ionic liquid (IL) can electrostatically induce charge carriers and/or intercalate ions in and out of the lattice which can trigger a large change of the electronic, optical, and magnetic properties of materials and even modify the crystal structure. We present a systematic study of ionic liquid gating of exfoliated 2D molybdenum trioxide (MoO 3 ) devices and correlate the resultant electrical properties to the electrochemical doping via ion migration during the IL biasing process. A nearly 9 orders of magnitude modulation of the MoO 3 conductivity is obtained for the two types of ionic liquids that are investigated. In addition, notably rapid on/off switching was realized through a lithium-containing ionic liquid whereas much slower modulation was induced via oxygen extraction/intercalation. Time of flight-secondary ion mass spectrometry confirms the Li intercalation. Density functional theory (DFT) calculations have been carried out to examine the underlying metallization mechanism. Results of short-pulse tests show the potential of these MoO 3 devices as neuromorphic computing elements due to their synaptic plasticity.

Most studied two-dimensional (2D) materials exhibit isotropic behavior due to high lattice symmetry; however, lower-symmetry 2D materials such as phosphorene and other elemental 2D materials exhibit very interesting anisotropic properties. In this work, we report the atomic structure, electronic properties, and vibrational modes of few-layered PdSe 2 exfoliated from bulk crystals, a pentagonal 2D layered noble transition metal dichalcogenide with a puckered morphology that is air-stable. Micro-absorption optical spectroscopy and first-principles calculations reveal a wide band gap variation in this material from 0 (bulk) to 1.3 eV (monolayer). The Raman-active vibrational modes of PdSe 2 were identified using polarized Raman spectroscopy, and a strong interlayer interaction was revealed from large, thickness-dependent Raman peak shifts, agreeing with first-principles Raman simulations. Field-effect transistors made from the few-layer PdSe 2 display tunable ambipolar charge carrier conduction with a high electron field-effect mobility of ∼158 cm 2 V -1 s -1 , indicating the promise of this anisotropic, air-stable, pentagonal 2D material for 2D electronics.