Observed Trajectories of Cannabis Use and Concurrent Longitudinal Outcomes in Youth and Young Adults Receiving Coordinated Specialty Care for Early Psychosis

Cannabis use is present and persistent in young adults with early psychosis receiving Coordinated Specialty Care (CSC) in the United States. While CSC programs are effective in improving quality of life, helping individuals reach goals, and promoting recovery, cannabis use may limit the extent of these improvements. This study extended upon previous findings to examine trajectories of cannabis use among individuals with early psychosis. The sample consisted of 1325 CSC participants enrolled for more than one year at OnTrackNY and followed up to two years, categorized into three groups: no use, reduced use, and persistent use. Baseline demographic and clinical differences were compared across groups and associations between clinical and psychosocial outcomes at 12 months and 24 months were examined across groups. Of the sample, 40 % remained persistent users over two years while 12.8 % reduced their use. At baseline, persistent users were younger (p = 0.011), more likely to be male (p < 0.001), had lower education levels (p = 0.019), and were more likely to have had past legal issues prior to admission (p < 0.001) than non-users. At 2 years, persistent users had significantly worse symptom scores than non-users (p = 0.0003) and reduced users (p = 0.0004). These findings highlight the presence of persistent cannabis use being common in this population and the need to improve substance use treatment offered to allow more CSC participants to achieve improved outcomes.

Hydrogen sulfide dysfunction in metabolic syndrome-associated vascular complications involves cGMP regulation through soluble guanylyl cyclase persulfidation

Here, by using in vitro and ex vivo approaches, we elucidate the impairment of the hydrogen sulfide (H2S) pathway in vascular complications associated with metabolic syndrome (MetS). In the in vitro model simulating hyperlipidemic/hyperglycemic conditions, we observe significant hallmarks of endothelial dysfunction, including eNOS/NO signaling impairment, ROS overproduction, and a reduction in CSE-derived H2S. Transitioning to an ex vivo model using db/db mice, a genetic MetS model, we identify a downregulation of CBS and CSE expression in aorta, coupled with a diminished L-cysteine-induced vasorelaxation. Molecular mechanisms of eNOS/NO signaling impairment, dissected using pharmacological and molecular approaches, indicate an altered eNOS/Cav-1 ratio, along with reduced Ach- and Iso-induced vasorelaxation and increased L-NIO-induced contraction. In vivo treatment with the H2S donor Erucin ameliorates vascular dysfunction observed in db/db mice without impacting eNOS, further highlighting a specific action on smooth muscle component rather than the endothelium. Analyzing the NO signaling pathway in db/db mice aortas, reduced cGMP levels were detected, implicating a defective sGC/cGMP signaling. In vivo Erucin administration restores cGMP content. This beneficial effect involves an increased sGC activity, due to enzyme persulfidation observed in sGC overexpressed cells, coupled with PDE5 inhibition. In conclusion, our study demonstrates a pivotal role of reduced cGMP levels in impaired vasorelaxation in a murine model of MetS involving an impairment of both H2S and NO signaling. Exogenous H2S supplementation through Erucin represents a promising alternative in MetS therapy, targeting smooth muscle cells and supporting the importance of lifestyle and nutrition in managing MetS.

1255 IMPROVING COMMUNICATION BETWEEN NEXT OF KIN AND MEDICAL STAFF FOR OUR MOST VULNERABLE PATIENTS: A QUALITY IMPROVEMENT PROJECT

Background

This project was completed by a team of junior doctors working across two general medical wards at Queen Alexandra Hospital.

Introduction

Due to persistently high bed occupancy, patients are increasingly subject to multiple moves, increasing the risk of missed or delayed communication (Toye C et al, Clin interv aging, 2019, 14, 2223-2237). Importantly, families who receive good communication from staff are more likely to feel satisfied with the care of their loved one (Ersek M et al, J pain symptom manage, 2021, 62(2), 213–222). Our aim was to increase the occurrence and comprehensiveness of documented discussions between next of kin (NOK) and the medical team, especially in vulnerable patients who may be unable to advocate for themselves.

Methods

We conducted a retrospective, cross-sectional analysis of patient notes across two PDSA cycles. NICE guidelines NG27, NG97 and NG96 provided an audit standard. Patients were identified as at-risk of poor communication if diagnosed with dementia, cognitive impairment, addiction, learning difficulties or needing an interpreter. Targeted intervention prior to re-audit included education of the medical team and introduction of a written prompt within the patient’s notes.

Results

25/55 patients were identified as at-risk in cycle one, with 39/71 patients at-risk in cycle two. Post-intervention, the number of at-risk patients with a documented NOK discussion increased from 74% to 82%. Patient treatment plan discussions increased from 81% to 97%. Discussions, where applicable, regarding escalation of care, Deprivation of Liberty Safeguards (DoLS), capacity and Mental Health Act (MHA) slightly decreased. Conversations regarding patient consent for data sharing were rarely documented.

Conclusion

Our intervention increased the proportion of documented patient discussions; however, it did highlight the need to improve the frequency of documented conversations surrounding escalation of care, DoLS, capacity and MHA. This has provided impetus for further improvement projects.

Evaluation of reliability index and probability of failure for the improvement of the Nigerian empirical mechanistic flexible pavement analysis and design system (Nempads)

The aim of this work was to evaluate reliability index (RI) with respect to fatigue and rutting within the different seasons peculiar to Nigeria, in order to improve Empirical-Mechanistic flexible pavement design approach, using First Order Reliability Method (FORM). Flexible pavement design involves many uncertainties, variabilities, and approximations regarding the input parameters like material properties, traffic loads. Others include subgrade strength, drainage conditions, construction, compaction procedures and climatic factors such as temperature, rainfall, and snowfall, etc. The combination of the variances associated with input parameters contributes to components and system uncertainty, and this combination of variances can have a significant effect on the predicted performance of the pavement. Reliability in pavement design is introduced to consider these uncertainties. Layers thicknesses, material properties, and Equivalent Standard Axle Load (ESAL) were entered into a multi-layer elastic theory software, ELSYM-5, which in turn were used to calculate strains and stresses for different seasons. The results obtained were entered into Nigerian fitted transfer function distress models to compute allowable ESALS. Miner’s hypothesis theory equation was used to calculate the cumulative damage due to stress and strains generated. A Framework was generated for finding individual reliability index (RI), systemic reliability index (SRI), and probability of failure. The findings showed that Season I (Winter) recorded the highest component reliability index for fatigue (5.63 for Normal Distribution). Season II (Summer) recorded the lowest component reliability index (β) for rutting (5.4 for Normal Distribution). Season III (Spring) recorded the lowest component reliability index for fatigue (1.85 for Normal Distribution)

Creep and morphological evaluation of polypropylene waste modified asphalt for pavement applications

Synoptic findings by researchers have revealed tremendous physic-chemical improvements of polymer modified mixes over the conventional asphalt. Traditionally, laboratory mechanical properties were carried out for asphalt testing, but cannot calibrate simple performance test (SPTs) criteria for fatigue and field performance. Marshall test-sized specimens of polymer asphalt mixtures were engineered with arbitrary contents of 0 to 3.0% polypropylene waste admixed with 4.5 to 6.5% bitumen contents based on relevant literature. Creep deformation involves uniaxial static creep (USC) test using BS 598-111. Morphological examinations were test with Hitachi S-4700 field-emission scan-electron-microscope (FE-SEM). Thirdly, thermal degradation was determined using Shimadzu TGA-50 thermo-gravimetric analyzer. The results showed creep resistivity with fatigue recovery of 23.2% and 28.9% strain reduction at 10oC and 60oC respectively from the optimal 2.0% polypropylene and 6.0% bitumen compared to the control mix. Also, the same mix produced well dispersed and better enhanced pore packaging micro-structure capable of resisting ageing volatization under severe traffic and environmental loading conditions considered. Keywords: Asphalt pavement, polypropylene, creep deformation, age volatization and microstructure

Carbon Dots as Fillers Inducing Healing/Self-Healing and Anticorrosion Properties in Polymers

Self-healing is the way by which nature repairs damage and prolongs the life of bio entities. A variety of practical applications require self-healing materials in general and self-healing polymers in particular. Different (complex) methods provide the rebonding of broken bonds, suppressing crack, or local damage propagation. Here, a simple, versatile, and cost-effective methodology is reported for initiating healing in bulk polymers and self-healing and anticorrosion properties in polymer coatings: introduction of carbon dots (CDs), 5 nm sized carbon nanocrystallites, into the polymer matrix forming a composite. The CDs are blended into polymethacrylate, polyurethane, and other common polymers. The healing/self-healing process is initiated by interfacial bonding (covalent, hydrogen, and van der Waals bonding) between the CDs and the polymer matrix and can be optimized by modifying the functional groups which terminate the CDs. The healing properties of the bulk polymer-CD composites are evaluated by comparing the tensile strength of pristine (bulk and coatings) composites to those of fractured composites that are healed and by following the self-healing of scratches intentionally introduced to polymer-CD composite coatings. The composite coatings not only possess self-healing properties but also have superior anticorrosion properties compared to those of the pure polymer coatings.

Mapping vulnerability to bipolar disorders

Introduction

Although early interventions in individuals with bipolar disorder may reduce the associated personal and economic burden, the neurobiologic markers of enhanced risk are unknown.

Objectives

The objective of this paper is to analyze the existence of neurobiological abnormalities in individuals with genetic risk for developing bipolar disorder (HR)

Material and methods

A literature search was performed in the available scientific literature on the subject study object, by searching MEDLINE.

Results

There were 37 studies included in this systematic review. The overall sample for the systematic review included 1258 controls and 996 HR individuals. No significant differences were detected between HR individuals and controls in the selected ROIs (regions of interest): striatum, amygdala, hippocampus, pituitary and frontal lobe. The HR group showed increased grey matter volume compared with patients with established bipolar disorder. The HR individuals showed increased neural response in the left superior frontal gyrus, medial frontal gyrus and left insula compared with controls. The overall results found no significant differences between individuals at high genetic risk and controls since the magnitude of the association as corresponds to an OR < 1.5 (low association)

Conclusion

There is accumulating evidence for the existence of neurobiologic abnormalities in individuals at genetic risk for bipolar disorder at various scales of investigation. The etiopathogenesis of bipolar disorder will be better elucidated by future imaging studies investigating larger and more homogeneous samples and using longitudinal designs to dissect neurobiologic abnormalities that are underlying traits of the illness from those related to psychopathologic states, such as episodes of mood exacerbation or pharmacologic treatment.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Cocaine use and employment

Introduction

Cocaine use is prevalent in mental health consultations in both sexes. However, in men and women there are differences in the frequency of use of substances and on the employment situation.

Objectives

Show the differences for the use of cocaine and employment status of men and women, in a sample of patients followed at the Mental Health Center in Drug Dependency Unit.

Material and methods

We conducted a cross-sectional study and analyze the differences according to sex for cocaine use and the employment situation, in a sample of patients who are undergoing treatment at the Mental Health Center for a year diagnosed with dual pathology.

Results

In men in active employment status, the percentage of cocaine use is 19.5% and if we compare with women in the same job situation, the percentage of cocaine use is 0%.

Men who are unemployed use more cocaine than women in the same job situation. For retirees, the highest percentage of cocaine is found in women.

Hundred percent of women use cocaine by sniffing. Men use different ways of cocaine consume.

Snorted way 67.7%, 14.9% smoked and snorted, smoked 8% and 2.3% intravenous.

Conclusion

Men use cocaine more frequently unemployed while women do more it often being retired.

The route most used cocaine consume in both sexes is snorted.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Construction and evaluation of high-quality n-ZnO nanorod/p-diamond heterojunctions

Vertically-aligned ZnO nanorods (NRs) arrays were synthesized by a low-temperature solution method on boron-doped diamond (BDD) films. The morphology, growth direction, and crystallinity of the ZnO NRs were studied by scanning electron microscopy, X-ray diffraction and cathodoluminescence. Electrical characterization of the ZnO NR/BBD heterostructures revealed characteristic p-n junction properties with an on/off ratio of about 50 at +/- 4 V and a small reverse leakage current approximately 1 microA. Moreover, the junctions showed an ideality factor around 1.0 at a low forward voltage from 0 to 0.3 V and about 2.1 for an increased voltage ranging from 1.2 to 3.0 V, being consistent with that of an ideal diode according to the Sah-Noyce-Shockley theory.

Controlled growth of ZnO/Zn₁-xPbxSe core-shell nanowires and their interfacial electronic energy alignment

ZnO/Zn(1-x)Pb(x)Se core-shell nanowires (NWs) have been synthesized by a solution based surface ion transfer method at various temperatures. The energy dispersive spectroscopic (EDS) mapping of single NWs suggests that the Zn, Pb and Se atoms are uniformly distributed in their shell layers. The ternary Zn(1-x)Pb(x)Se layers with tunable bandgaps extend the band-edge of optical absorption from 450 nm to 700 nm contrasting with the binary ZnSe layers. The ultraviolet photoelectron spectroscopic (UPS) analysis reveals a transition from the type I to type II band alignment when the x fraction decreases from 0.66 to the value of 0.36 in the nanoshell layers. This quantitative investigation of electronic energy levels at ZnO and Zn(1-x)Pb(x)Se interfaces indicates that the proper type II band alignment is well suited for photovoltaic energy conversion. The photovoltaic cells comprising a ZnO/Zn(1-x)Pb(x)Se nano-heterojunction with the optimized Pb content are expected to be more efficient than the devices sensitized by binary ZnSe or PbSe.

Visible-NIR photodetectors based on CdTe nanoribbons

Zinc blende-structured CdTe nanoribbons (NRs) were synthesized for the first time via a two-step process. The electronic, transport, and photoconductive properties of the CdTe NRs were studied systematically. It was revealed that the CdTe NRs showed p-type conductivity, and presented significant photoresponses to visible-NIR (400-800 nm) irradiation with high responsivity and gain. The contribution of the factors such as surface states of NRs, channel length, light intensity, and working bias voltage to the photoresponse characteristics of CdTe NR photodetectors were discussed. Moreover, single CdTe NR-based visible-NIR photodetectors were also demonstrated to have high stability and reliability.

Tunable band gaps and p-type transport properties of boron-doped graphenes by controllable ion doping using reactive microwave plasma

We report tunable band gaps and transport properties of B-doped graphenes that were achieved via controllable doping through reaction with the ion atmosphere of trimethylboron decomposed by microwave plasma. Both electron energy loss spectroscopy and X-ray photoemission spectroscopy analyses of the graphene reacted with ion atmosphere showed that B atoms are substitutionally incorporated into graphenes without segregation of B domains. The B content was adjusted over a range of 0-13.85 atom % by controlling the ion reaction time, from which the doping effects on transport properties were quantitatively evaluated. Electrical measurements from graphene field-effect transistors show that the B-doped graphenes have a distinct p-type conductivity with a current on/off ratio higher than 10(2). Especially, the band gap of graphenes is tuned from 0 to ~0.54 eV with increasing B content, leading to a series of modulated transport properties. We believe the controllable doping for graphenes with predictable transport properties may pave a way for the development of graphene-based devices.

Facile and rapid synthesis of highly porous wirelike TiO2 as anodes for lithium-ion batteries

Highly porous wirelike TiO(2) nanostructures have been synthesized by a simple two-step process. The morphological and structural characterizations reveal that the TiO(2) wires typically have diameters from 0.4 to 2 μm, and lengths from 2 to 20 μm. The TiO(2) wires are highly porous and comprise of interconnected nanocrystals with diameters of 8 ± 2 nm resulting in a high specific surface area of 252 m(2) g(-1). The effects of experimental parameters on the structure and morphology of the porous wirelike TiO(2) have been investigated and the possible formation processes of these porous nanostructures are discussed. Galvanostatic charge/discharge tests indicate that the porous wirelike TiO(2) samples exhibit stable reversible lithium ion storage capacities of 167.1 ± 0.7, 152.1 ± 0.8, 139.7 ± 0.3, and 116.1 ± 1.1 mA h g(-1) at 0.5, 1, 2, and 5 C rates, respectively. Such improved performance could be ascribed to their unique porous and 1D nanostructures facilitating better electrolyte penetration, higher diffusion rate of electrons and lithium ion, and variation of accommodated volumes during the charge/discharge cycles.

Surface nanostructuring of boron-doped diamond films and their electrochemical performance

Uniform and vertically aligned nanocone and nanopillar arrays were successfully constructed on heavily boron-doped nanocrysatlline diamond films by carrying out bias-assisted reactive ion etching in hydrogen/argon plasmas. The electrochemical properties of the nanostructured boron-doped diamond films were investigated by cyclic voltammetry using 1 mM [Fe(CN)6](3-/4-) as redox couple. Compared to the planar boron-doped nanocrystalline diamond film electrode, the surface nanostructuring of boron-doped diamond film electrodes demonstrate enhanced sensitivity due to their enlarged electro-active surface areas. The results indicated that boron-doped diamond nanocones and nanopillars are promising electrode materials which benefit to improve the efficiency, sensitivity and reproducibility of biomedical and chemical sensors.

Violet-blue LEDs based on p-GaN/n-ZnO nanorods and their stability

In this paper, we report a fabrication, characterization and stability study of p-GaN/n-ZnO nanorod heterojunction light-emitting devices (LEDs). The LEDs were assembled from arrays of n-ZnO vertical nanorods epitaxially grown on p-GaN. LEDs showed bright electroluminescence in blue (440 nm), although weaker violet (372 nm) and green-yellow (550 nm) spectral components were also observed. The device characteristics are generally stable and reproducible. The LEDs have a low turn-on voltage (∼5 V). The electroluminescence (EL) is intense enough to be noticed by the naked eye, at an injection current as low as ∼ 40 µA (2.1 × 10(-2) A cm(-2) at 7 V bias). Analysis of the materials, electrical and EL investigations point to the role of a high quality of p-n nano-heterojunction which facilitates a large rectification ratio (320) and a stable reverse current of 2.8 µA (1.4 × 10(-3) A cm(-2) at 5 V). Stability of EL characteristics was investigated in detail. EL intensity showed systematic degradation over a short duration when the LED was bias-stressed at 30 V. At smaller bias (<20 V) LEDs tend to show a stable and repeatable EL characteristic. Thus a simple low temperature solution growth method was successfully exploited to realize nanorod/film heterojunction LED devices with predictable characteristics.

Tunable p-type conductivity and transport properties of AlN nanowires via Mg doping

Arrays of well-aligned AlN nanowires (NWs) with tunable p-type conductivity were synthesized on Si(111) substrates using bis(cyclopentadienyl)magnesium (Cp(2)Mg) vapor as a doping source by chemical vapor deposition. The Mg-doped AlN NWs are single-crystalline and grow along the [001] direction. Gate-voltage-dependent transport measurements on field-effect transistors constructed from individual NWs revealed the transition from n-type conductivity in the undoped AlN NWs to p-type conductivity in the Mg-doped NWs. By adjusting the doping gas flow rate (0-10 sccm), the conductivity of AlN NWs can be tuned over 7 orders of magnitude from (3.8-8.5) × 10(-6) Ω(-1) cm(-1) for the undoped sample to 15.6-24.4 Ω(-1) cm(-1) for the Mg-doped AlN NWs. Hole concentration as high as 4.7 × 10(19) cm(-3) was achieved for the heaviest doping. In addition, the maximum hole mobility (∼6.4 cm(2)/V s) in p-type AlN NWs is much higher than that of Mg-doped AlN films (∼1.0 cm(2)/V s). (2) The realization of p-type AlN NWs with tunable electrical transport properties may open great potential in developing practical nanodevices such as deep-UV light-emitting diodes and photodetectors.

Construct hierarchical superhydrophobic silicon surfaces by chemical etching

We present a simple approach for preparing hydrophobic silicon surfaces by constructing silicon nanowire arrays using Ag-assisted chemical etching without low-surface-energy material modification. The static and dynamic wetting properties of the nanostructured surfaces and their dependence on etching conditions were studied. It was revealed that the surface topologies of silicon nanowire arrays and their corresponding wetting properties could be tuned by varying the etching time. Under optimized etching conditions, superhydrophobic surfaces with an apparent contact angle larger than 150 degrees and a sliding angle smaller than 10 degrees were achieved due to the formation of a hierarchical structure. The origin of hydrophobic behavior was discussed based on Wenzel and Cassie models. In addition, the effects of surface modification of Si surface nanostructures on their hydrophobic characteristics were also investigated.

Large Scale Synthesis of Silicon Nanowires by Laser Ablation

Quasi one-dimensional materials have attracted considerable attention in recent years because of its potential to both fundamental physics and nanoelectronic applications. More recently, we have achieved large scale synthesis of silicon nanowires (SINW) at a high growth rate by laser ablation of Si target at 1200 °C. The laser source was a pulsed KrF excimer laser and the Si targets were made by pressing Si powder of 5 microns in size. 50 sccm Ar was used as a carrying gas flowing from the side near the Si target towards a water-cooled copper finger. Si nanowires have been grown with diameters ranging from 3 to 43 nm and several hundreds microns in length after 2 hours of laser ablation of Si target. The SLNWs were analyzed by XRD, Raman, EDS, TEM and HRTEM. Successful large scale synthesis of SINW by laser ablation extends the pulsed laser ablation method from depositing thin films to synthesis of nanowires.

Incorporation of graphenes in nanostructured TiO(2) films via molecular grafting for dye-sensitized solar cell application

This paper presents a systematic investigation on the incorporation of chemical exfoliation graphene sheets (GS) in TiO(2) nanoparticle films via a molecular grafting method for dye-sensitized solar cells (DSSCs). By controlling the oxidation time in the chemical exfoliation process, both high conductivity of reduced GS and good attachment of TiO(2) nanoparticles on the GS were achieved. Uniform GS/TiO(2) composite films with large areas on conductive glass were prepared by electrophoretic deposition, and the incorporation of GS significantly improved the conductivity of the TiO(2) nanoparticle film by more than 2 orders of magnitude. Moreover, the power conversion efficiency for DSSC based on GS/TiO(2) composite films is more than 5 times higher than that based on TiO(2) alone, indicating that the incorporation of GS is an efficient means for enhancing the photovoltaic (PV) performance. The better PV performance of GS/TiO(2) DSSC is also attributed to the better dye loading of GS/TiO(2) film than that of TiO(2) film. The effect of GS content on the PV performances was also investigated. It was found that the power conversion efficiency increased first and then decreased with the increasing of GS concentration due to the decrease in the transmittance at high GS content. Further improvements can be expected by fully optimizing fabrication conditions and device configuration, such as increasing dye loading via thicker films. The present synthetic strategy is expected to lead to a family of composites with designed properties.

Tunable electrical properties of silicon nanowires via surface-ambient chemistry

p-Type surface conductivity is a uniquely important property of hydrogen-terminated diamond surfaces. In this work, we report similar surface-dominated electrical properties in silicon nanowires (SiNWs). Significantly, we demonstrate tunable and reversible transition of p(+)-p-i-n-n(+) conductance in nominally intrinsic SiNWs via changing surface conditions, in sharp contrast to the only p-type conduction observed on diamond surfaces. On the basis of Si band energies and the electrochemical potentials of the ambient (pH value)-determined adsorbed aqueous layer, we propose an electron-transfer-dominated surface doping model, which can satisfactorily explain both diamond and silicon surface conductivity. The totality of our observations suggests that nanomaterials can be described as a core-shell structure due to their large surface-to-volume ratio. Consequently, controlling the surface or shell in the core-shell model represents a universal way to tune the properties of nanostructures, such as via surface-transfer doping, and is crucial for the development of nanostructure-based devices.

Field electron emission of ZnO nanowire pyramidal bundle arrays

A facile hydrothermal method was adopted to in situ grow ZnO nanowire pyramidal bundle arrays on zinc substrates at low growth temperature without the assistance of catalysts and templates. The bundle arrays were shown to form by sticking of nanowires at their tips. Field electron emission characterization of nanowires bundle arrays revealed a very low turn-on electric field of about 2.3 V/microm and a threshold electric field (corresponding to the field electron emission current density of 10 mA/cm2) of 6.8 V/microm, which are comparable to those observed in carbon nanotube arrays. The bundle arrays also show pronounced long-term field electron emission stability at a high current density. In addition, the formation mechanism of the pyramidal bundled arrays and the origin of the peculiar field electron emission properties were discussed.

The fabrication of cubic boron nitride nanocone and nanopillar arrays via reactive ion etching

High-density (2 x 10(9) cm(-2)) uniform arrays of cubic boron nitride (cBN) nanocones and nanopillars with a high aspect ratio were fabricated by employing sequential growth and bias-assisted reactive ion etching using gold nano-dots as an etching mask. The mechanism of formation of the nanopillar and nanocone morphologies was discussed in terms of the relative action of ion bombardment etching and chemical etching due to activated hydrogen plasma constituents. The presented method enabled nanostructuring of cBN surfaces over large areas with great uniformity and reproducibility with a controlled aspect ratio. The unique morphology of the nanostructures offers diverse application opportunities in microelectromechanical devices.

High-quality Graphenes via a facile quenching method for field-effect transistors

Single- and few-layer graphene sheets with sizes up to 0.1 mm were fabricated by simply quenching hot graphite in an ammonium hydrogen carbonate aqueous solution. The identity and thickness of graphene sheets were characterized with transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. In addition to its simplicity and scalability, the present synthesis can produce graphene sheets with excellent qualities in terms of sizes, purity, and crystal quality. The as-produced graphene sheets can be easily transferred to solid substrates for further processing. Field-effect transistors based on individual graphenes were fabricated and shown to have high ambipolar carrier mobilities.

Vertically aligned p-type single-crystalline GaN nanorod arrays on n-type Si for heterojunction photovoltaic cells

Vertically aligned Mg-doped GaN nanorods have been epitaxially grown on n-type Si substrate to form a heterostructure for fabricating p-n heterojunction photovoltaic cells. The p-type GaN nanorod/n-Si heterojunction cell shows a well-defined rectifying behavior with a rectification ratio larger than 10(4) in dark. The cell has a high short-circuit photocurrent density of 7.6 mAlcm2 and energy conversion efficiency of 2.73% under AM 1.5G illumination at 100 mW/cm2. Moreover, the nanorod array may be used as an antireflection coating for solar cell applications to effectively reduce light loss due to reflection. This study provides an experimental demonstration for integrating one-dimensional nanostructure arrays with the substrate to directly fabricate heterojunction photovoltaic cells.

Investigation of low-resistivity from hydrogenated lightly B-doped diamond by ion implantation

We have implanted boron (B) ions (dosage: 5×1014 cm-2) into diamond and then hydrogenated the sample by implantating hydrogen ions at room temperature. A p-type diamond material with a low resistivity of 7.37 mΩ cm has been obtained in our experiment, which suggests that the hydrogenation of B-doped diamond results in a low-resistivity p-type material. Interestingly, inverse annealing, in which carrier concentration decreased with increasing annealing temperature, was observed at annealing temperatures above 600 °C. In addition, the formation mechanism of a low-resistivity material has been studied by density functional theory calculation using a plane wave method.

An alternative approach to carbon nanotube sample preparation for TEM investigation

A two-stage replication technique (positive replica) is shown to be suitable for transmission electron microscopy (TEM) examination of carbon nanotubes (CNTs) and other one-dimensional nanostructures in their longitudinal direction. This method enables handling the fragile nanostructures, is fast and simple and allows to study the growth mechanism of nanofeatures, including the early stages of their growth. CNTs may also be examined when the growth layers are very thin, and even when only a few nanotubes are on a substrate. Replicas can be taken from various substrate shapes covered with nanostructures and from minute or specifically selected areas of the substrates. CNTs extracted by the replica are not disturbed, and their nanostructures are preserved. It is demonstrated that using positive replicas, HRTEM images from the nanosized carbon forms can also be obtained.

Cubic Phase Content and Structure of BN Films from an X-ray Absorption Study

X-ray absorption near-edge structure (XANES) was used to study the cubic boron nitride (c-BN) content in the BN films deposited on various substrates by different physical vapor deposition or plasma-enhanced chemical vapor deposition methods. By fitting the XANES curves of thin-film samples using standard spectra of pure c-BN and sp(2)-bonded BN in the films with suitable weight factors, the c-BN contents at the film's surface region and across the film's thickness have been determined quantitatively. The results agree well with the previous transmission electron microscopic observations. The method is proved to be independent of the optical properties of thin film and provides a possibility to evaluate the cubic content of BN films accurately.

Ab Initio and Variational Transition State Approach to β-C3N4 Formation: Kinetics for the Reaction of CH3NH2 with H

The CH3NH2 molecule has been considered as either an important intermediate in methane and ammonia mixtures or a precursor in methylamine and hydrogen mixtures in the synthesis of carbon nitride thin films. The fast Hydrogen (H) abstraction from CH3NH2 is an important process involved in the formation of HCN or CNH in the chemical vapor deposition (CVD) of carbon nitride thin films. The energetic and kinetic characteristics of the H abstraction reaction from CH3NH2 by atomic H used in CVD of beta-C3N4 were studied using ab initio direct dynamics methods for the first time. Two primary processes were identified for this reaction: H abstraction from the CH3 group and H abstraction from the NH2 group. On the basis of ab initio data, the rate constants of each channel have been deduced by canonical variational transition state theory with small-curvature tunneling correction over a wide temperature range of 200 to approximately 3000 K. The theoretical results were compared with available experimental data.

Studying the Growth of Cubic Boron Nitride on Amorphous Tetrahedral Carbon Interlayers

The growth of cubic boron nitride (cBN) films on bare silicon and amorphous tetrahedral carbon (ta-C) layers prepared on silicon substrates was studied. The cBN films were prepared by radio frequency magnetron sputter deposition at approximately 870 degrees C. The original ta-C interlayers were graphitized and restructured under high temperature and possibly under ion bombardment during BN deposition. The majority of graphitic basal planes were nearly perpendicular to the surface of silicon substrates. The BN films grown on these restructured carbon layers were deposited with higher content of cubic phase and did not show delamination signs. Turbostratic BN (tBN) basal planes extended carbon basal planes and their edges served as cBN nucleation sites. The cBN films grown on textured ta-C interlayers were insensitive to the ambient environment. The residual sp(3)-bonded carbon phase confined in the interlayers probably acts as a diffusion barrier preventing the oxidation of dangling bonds near BN interface and thus precludes weakening the interface as a result of volume expansion. The carbon interlayers also improve the crystallinity of the oriented tBN because they are continuation of carbon graphitic basal planes so that the volume fraction of nitrogen-void (N-void) defects in the sp(2)-bonded BN intermediate layers is reduced. The strong sp(3)-bonded carbon matrix could thereto withstand large compressive stress and facilitates deposition of thicker cBN films.

Interfacial Study of Cubic Boron Nitride Films Deposited on Diamond

We have studied the nucleation and growth of cubic boron nitride (cBN) films deposited on silicon and diamond-coated silicon substrates using fluorine-assisted chemical vapor deposition (CVD). These comparative studies substantiate that the incubation amorphous/turbostratic BN layers, essential for the cBN nucleation on silicon, are not vital precursors for cBN nucleation on diamond, and they are inherently eliminated. At vastly reduced critical bias voltage, down to -10 V, cBN growth is still maintained on diamond surfaces, and cBN and underlying diamond crystallites exhibit an epitaxial relationship. However, the epitaxial growth is associated with stress in the cBN-diamond interfacial region. In addition, some twinning of crystallites and small-angle grain boundaries are observed between the cBN and diamond crystallites because of the slight lattice mismatch of 1.36%. The small-angle grain boundaries could be eliminated by imposing a little higher bias voltage during the initial growth stage. The heteroepitaxial growth of cBN films on different substrate materials are discussed in the view of lattice matching, surface-energy compatibility, and stability of the substrate against ion irradiation.