Hypoglycaemia frequency and physiological response after double or triple doses of once-weekly insulin icodec vs once-daily insulin glargine U100 in type 2 diabetes: a randomised crossover trial.

AIMS/HYPOTHESIS: This study compared the frequency of hypoglycaemia, time to hypoglycaemia and recovery from hypoglycaemia after double or triple doses of once-weekly insulin icodec vs once-daily insulin glargine U100. Furthermore, the symptomatic and counterregulatory responses to hypoglycaemia were compared between icodec and glargine U100 treatment. METHODS: In a randomised, single-centre (Department of Internal Medicine, Division of Endocrinology and Diabetology, Medical University of Graz, Graz, Austria), open-label, two-period crossover trial, individuals with type 2 diabetes (age 18-72 years, BMI 18.5-37.9 kg/m2, HbA1c ≤75 mmol/mol [≤9.0%]) treated with basal insulin with or without oral glucose-lowering drugs received once-weekly icodec (for 6 weeks) and once-daily glargine U100 (for 11 days). Total weekly doses were equimolar based on individual titration of daily glargine U100 during the run-in period (target fasting plasma glucose [PG]: 4.4-7.2 mmol/l). Randomisation was carried out by assigning a randomisation number to each participant in ascending order, which encoded to one of two treatment sequences via a randomisation list prepared prior to the start of the trial. At steady state, double and triple doses of icodec and glargine U100 were administered followed by hypoglycaemia induction: first, euglycaemia was maintained at 5.5 mmol/l by variable i.v. infusion of glucose; glucose infusion was then terminated, allowing PG to decrease to no less than 2.5 mmol/l (target PGnadir). The PGnadir was maintained for 15 min. Euglycaemia was restored by constant i.v. glucose (5.5 mg kg-1 min-1). Hypoglycaemic symptoms score (HSS), counterregulatory hormones, vital signs and cognitive function were assessed at predefined PG levels towards the PGnadir. RESULTS: Hypoglycaemia induction was initiated in 43 and 42 participants after double dose of icodec and glargine U100, respectively, and in 38 and 40 participants after triple doses, respectively. Clinically significant hypoglycaemia, defined as PGnadir <3.0 mmol/l, occurred in comparable proportions of individuals treated with icodec vs glargine U100 after double (17 [39.5%] vs 15 [35.7%]; p=0.63) and triple (20 [52.6%] vs 28 [70.0%]; p=0.14) doses. No statistically significant treatment differences were observed in the time to decline from PG values of 5.5 mmol/l to 3.0 mmol/l (2.9-4.5 h after double dose and 2.2-2.4 h after triple dose of the insulin products). The proportion of participants with PGnadir ≤2.5 mmol/l was comparable between treatments after double dose (2 [4.7%] for icodec vs 3 [7.1%] for glargine U100; p=0.63) but higher for glargine U100 after triple dose (1 [2.6%] vs 10 [25.0%]; p=0.03). Recovery from hypoglycaemia by constant i.v. glucose infusion took <30 min for all treatments. Analyses of the physiological response to hypoglycaemia only included data from participants with PGnadir <3.0 mmol/l and/or the presence of hypoglycaemic symptoms; in total 20 (46.5%) and 19 (45.2%) individuals were included after a double dose of icodec and glargine U100, respectively, and 20 (52.6%) and 29 (72.5%) individuals were included after a triple dose of icodec and glargine U100, respectively. All counterregulatory hormones (glucagon, adrenaline [epinephrine], noradrenaline [norepinephrine], cortisol and growth hormone) increased during hypoglycaemia induction with both insulin products at both doses. Following triple doses, the hormone response was greater with icodec vs glargine U100 for adrenaline at PG3.0 mmol/l (treatment ratio 2.54 [95% CI 1.69, 3.82]; p<0.001), and cortisol at PG3.0 mmol/l (treatment ratio 1.64 [95% CI 1.13, 2.38]; p=0.01) and PGnadir (treatment ratio 1.80 [95% CI 1.09, 2.97]; p=0.02). There were no statistically significant treatment differences in the HSS, vital signs and cognitive function. CONCLUSIONS/INTERPRETATION: Double or triple doses of once-weekly icodec lead to a similar risk of hypoglycaemia compared with double or triple doses of once-daily glargine U100. During hypoglycaemia, comparable symptomatic and moderately greater endocrine responses are elicited by icodec vs glargine U100. TRIAL REGISTRATION: ClinicalTrials.gov NCT03945656. FUNDING: This study was funded by Novo Nordisk A/S.

Once-Weekly Insulin Icodec vs Once-Daily Insulin Degludec in Adults With Insulin-Naive Type 2 Diabetes: The ONWARDS 3 Randomized Clinical Trial.

Importance: Once-weekly insulin icodec could provide a simpler dosing alternative to daily basal insulin in people with type 2 diabetes. Objective: To evaluate the efficacy and safety of once-weekly icodec vs once-daily insulin degludec in people with insulin-naive type 2 diabetes. Design, Setting, and Participants: Randomized, double-masked, noninferiority, treat-to-target, phase 3a trial conducted from March 2021 to June 2022 at 92 sites in 11 countries in adults with type 2 diabetes treated with any noninsulin glucose-lowering agents with hemoglobin A1c (HbA1c) of 7%-11% (53-97 mmol/mol). Interventions: Participants were randomly assigned in a 1:1 ratio to receive either once-weekly icodec and once-daily placebo (icodec group; n = 294) or once-daily degludec and once-weekly placebo (degludec group; n = 294). Main Outcomes and Measures: The primary end point was change in HbA1c from baseline to week 26 (noninferiority margin, 0.3% percentage points). Secondary end points included change in fasting plasma glucose from baseline to week 26, mean weekly insulin dose during the last 2 weeks of treatment, body weight change from baseline to week 26, and number of level 2 (clinically significant; glucose level <54 mg/dL) and level 3 (severe; requiring external assistance for recovery) hypoglycemic episodes. Results: Among 588 randomized participants (mean [SD] age, 58 [10] years; 219 [37%] women), 564 (96%) completed the trial. Mean HbA1c level decreased from 8.6% (observed) to 7.0% (estimated) at 26 weeks in the icodec group and from 8.5% (observed) to 7.2% (estimated) in the degludec group (estimated treatment difference [ETD], -0.2 [95% CI, -0.3 to -0.1] percentage points), confirming noninferiority (P < .001) and superiority (P = .002). There were no significant differences between the icodec and degludec groups for fasting plasma glucose change from baseline to week 26 (ETD, 0 [95% CI, -6 to 5] mg/dL; P = .90), mean weekly insulin dose during the last 2 weeks of treatment, or body weight change from baseline to week 26 (2.8 kg vs 2.3 kg; ETD, 0.46 [95% CI, -0.19 to 1.10] kg; P = .17). Combined level 2 or 3 hypoglycemia rates were numerically higher in the icodec group than the degludec group from week 0 to 31 (0.31 vs 0.15 events per patient-year exposure; P = .11) and statistically higher in the icodec group from week 0 to 26 (0.35 vs 0.12 events per patient-year exposure; P = .01). Conclusions and Relevance: Among people with insulin-naive type 2 diabetes, once-weekly icodec demonstrated superior HbA1c reduction to once-daily degludec after 26 weeks of treatment, with no difference in weight change and a higher rate of combined level 2 or 3 hypoglycemic events in the context of less than 1 event per patient-year exposure in both groups. Trial Registration: ClinicalTrials.gov Identifier: NCT04795531.

Insulin degludec versus insulin detemir, both in combination with insulin aspart, in the treatment of pregnant women with type 1 diabetes (EXPECT): an open­label, multinational, randomised, controlled, non-inferiority trial.

BACKGROUND: Insulin degludec (degludec) is a second-generation basal insulin with an improved pharmacokinetic-pharmacodynamic profile compared with first-generation basal insulins, but there are few data regarding its use during pregnancy. In this non-inferiority trial, we aimed to compare the efficacy and safety of degludec with insulin detemir (detemir), both in combination with insulin aspart (aspart), in pregnant women with type 1 diabetes. METHODS: This open-label, multinational, randomised, controlled, non-inferiority trial (EXPECT) was conducted at 56 sites (hospitals and medical centres) in 14 countries. Women aged at least 18 years with type 1 diabetes who were between gestational age 8 weeks (+0 days) and 13 weeks (+6 days) or planned to become pregnant were randomly assigned (1:1), via an interactive web response system, to degludec (100 U/mL) once daily or detemir (100 U/mL) once or twice daily, both with mealtime insulin aspart (100 U/mL), all via subcutaneous injection. Participants who were pregnant received the trial drug at randomisation, throughout pregnancy and until 28 days post-delivery (end of treatment). Participants not pregnant at randomisation initiated the trial drug before conception. The primary endpoint was the last planned HbA1c measurement before delivery (non-inferiority margin of 0·4% for degludec vs detemir). Secondary endpoints included efficacy, maternal safety, and pregnancy outcomes. The primary endpoint was assessed in all randomly assigned participants who were pregnant during the trial. Safety was assessed in all randomly assigned participants who were pregnant during the trial and exposed to at least one dose of trial drug. This study is registered with ClinicalTrials.gov, NCT03377699, and is now completed. FINDINGS: Between Nov 22, 2017, and Nov 8, 2019, from 296 women screened, 225 women were randomly assigned to degludec (n=111) or detemir (n=114). Mean HbA1c at pregnancy baseline was 6·6% (SD 0·6%; approximately 49 mmol/mol; SD 7 mmol/mol) in the degludec group and 6·5% (0·8%; approximately 48 mmol/mol; 9 mmol/mol) in the detemir group. Mean last planned HbA1c measurement before delivery was 6·2% (SE 0·07%; approximately 45 mmol/mol; SE 0·8 mmol/mol) in the degludec group and 6·3% (SE 0·07%; approximately 46 mmol/mol; SE 0·8 mmol/mol) in the detemir group (estimated treatment difference -0·11% [95% CI -0·31 to 0·08]; -1·2 mmol/mol [95% CI: -3·4 to 0·9]; pnon-inferiority<0·0001), confirming non-inferiority. Compared with detemir, no additional safety issues were observed with degludec. INTERPRETATION: In pregnant women with type 1 diabetes, degludec was found to be non-inferior to detemir. FUNDING: Novo Nordisk.

Poly(vinylidene fluoride)/partially alkylated poly(vinyl imidazole) interpolymer ultrafiltration membranes with intrinsic anti-biofouling and antifouling property for the removal of bacteria.

Bacterial contaminated water causes potential health issues. Conventional chlorine treatment has shortcomings of environmental hazards and chlorine adoptability by the bacterial cells. Ultrafiltration membrane can intercept bacterial species from feed water. Membrane having anti-biofouling/antifouling properties is needed for the removal of bacteria from feed water. Herein, interpolymer membranes with inherent antimicrobial activity and fouling release property have been prepared by the blend of poly(vinylidene fluoride) (PVDF), poly(vinyl pyrrolidone) and partially long chain alkylated (C12 chain) poly(vinyl imidazole) copolymer (PVIm-co-PVIm-C12) followed by cross-linking of the remaining VIm groups with an activated di-halide compound. The membranes obtain with copolymers of degree of alkyl substitution (DSC12) in the range of 0.75-0.85 and amount in the range of 0.9-3.5% w/w in the casting solutions exhibit good antimicrobial activity (>99 % of inhibition) and dynamic anti-biofouling property. The membrane prepared with 0.9% w/w of the copolymer (DSC12=0.85) shows higher flux recovery ratio (91 % for bacterial filtration and 88 % for protein filtration) compare to a pristine membrane (57 % for bacterial filtration and 58 % for protein filtration). The membrane is able to reject the bacteria completely. Use of small amount of copolymer and facile fabrication of stable anti-biofouling/antifouling membranes show potential for the purification of bacterial contaminated water.

Postprandial Glucose Excursions in Asian Versus Non-Asian Patients with Type 2 Diabetes: A Post Hoc Analysis of Baseline Data from Phase 3 Randomised Controlled Trials of IDegAsp.

INTRODUCTION: Increased postprandial glucose (PPG) is associated with high glycated haemoglobin levels and is an independent risk factor for cardiovascular diseases. The aim of this study was to compare PPG increments in Asian versus non-Asian adults with type 2 diabetes (T2D), who were insulin-naïve or insulin-experienced, from the phase 3 insulin degludec/insulin aspart (IDegAsp) clinical trials. METHODS: This was a post hoc analysis of data from 13 phase 3, randomised, parallel-group, open-label IDegAsp trials in patients with T2D. The pooled baseline clinical data were analysed for insulin-naïve and insulin-experienced groups; and each group was split into subgroups of Asian and non-Asian patients, respectively, and analysed accordingly. Baseline self-monitored blood glucose (SMBG) values at breakfast, lunch and the evening meal (before and 90 min after each meal) were used to assess PPG increments. The estimated differences in baseline SMBG increment between the Asian and non-Asian subgroups were analysed. RESULTS: Clinical data from 4750 participants (insulin-naïve, n = 1495; insulin-experienced, n = 3255) were evaluated. In the insulin-naïve group, the postprandial SMBG increment was significantly greater in the Asian versus the non-Asian subgroup at breakfast (estimated difference 28.67 mg/dL, 95% confidence interval [CI] 18.35, 38.99; p < 0.0001), lunch (17.34 mg/dL, 95% CI 6.47, 28.21; p = 0.0018) and the evening meal (16.19 mg/dL, 95% CI 5.04, 27.34; p = 0.0045). In the insulin-experienced group, the postprandial SMBG increment was significantly greater in the Asian versus non-Asian subgroup at breakfast (estimated difference 13.81 mg/dL, 95% CI 9.19, 18.44; p < 0.0001) and lunch (29.18 mg/dL, 95% CI 24.22, 34.14; p < 0.0001), but not significantly different at the evening meal. CONCLUSION: In this post hoc analysis, baseline PPG increments were significantly greater in Asian participants with T2D than in their non-Asian counterparts at all mealtimes, with the exception of the evening meal in insulin-experienced participants. Asian adults with T2D may benefit from the use of regimens that control PPG excursions. CLINICAL TRIAL NUMBERS: NCT02762578, NCT01814137, NCT01513590, NCT01009580, NCT01713530, NCT02648217, NCT01045447, NCT01365507, NCT01045707, NCT01272193, NCT01059812, NCT01680341, NCT02906917.

Mitigating artifacts by data driven identification & correction of rotational misalignment in gamma ray computed tomography.

Industrial Computed Tomography (ICT) is a radiation based cross sectional imaging technique that requires a sample to be manipulated precisely in a specific geometry to acquire analytically useful data. Unlike medical CT, industrial CT may require use of gamma radiation from radio-isotopes like Co60, Cs137 etc. having higher energy radiations for penetrating through higher density and thickness of material under inspection. Data acquisition in ICT involves use of a mechanical manipulator to rotate either the specimen or the source and detectors assembly in circular and linear geometry. Misalignment in mechanical set-up leads to significant artifacts in CT image. The effects may be even more pronounced in data acquired with discrete detector as against Linear Detector Array (LDA) because of certain built-in mechanical integrity associated with LDA. This paper discusses cross correlation based software correction method for combination of gamma ray source and NaI (Tl) scintillation detector based transmission ICT system in parallel beam CT geometry. The proposed correction does not require calibration of the set-up and any prior knowledge of the sample geometry or composition. This data driven correction yields improved CT reconstruction with limited data. The method is demonstrated with a mathematical simulation and applied to experimental data for validation.

Nanodiamonds as a state-of-the-art material for enhancing the gamma radiation resistance properties of polymeric membranes.

We report, for the first time, the development of gamma radiation resistant polysulfone (Psf)-nanodiamond (ND) composite membranes with varying concentrations of NDs, ranging up to 2 wt% of Psf. Radiation stability of the synthesized membranes was tested up to a dose of 1000 kGy. To understand the structure-property correlationship of these membranes, multiple characterization techniques were used, including field-emission scanning electron microscopy, atomic force microscopy, drop shape analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, gel permeation chromatography, positron annihilation spectroscopy, and small angle X-ray scattering. All the composite membranes exhibited enhanced radiation resistance properties, with 0.5% loading of NDs as the optimum. Compared to the radiation stability of Psf membranes up to a dose of 100 kGy, the optimum composite membranes are found to be stable up to a radiation dose of 500 kGy, owing to the unique surface chemistry of NDs and interfacial chemistry of Psf-ND composites. Experimental findings along with the Monte Carlo simulation studies confirmed a five times enhanced life-span of the composite membranes in an environment of the intermediate level radioactive waste, compared to the control Psf membrane.

Mixed-matrix membranes with enhanced antifouling activity: probing the surface-tailoring potential of Tiron and chromotropic acid for nano-TiO2.

Mixed-matrix membranes (MMMs) were developed by impregnating organofunctionalized nanoadditives within fouling-susceptible polysulfone matrix following the non-solvent induced phase separation (NIPS) method. The facile functionalization of nanoparticles of anatase TiO2 (nano-TiO2) by using two different organoligands, viz. Tiron and chromotropic acid, was carried out to obtain organofunctionalized nanoadditives, FT-nano-TiO2 and FC-nano-TiO2, respectively. The structural features of nanoadditives were evaluated by X-ray diffraction, X-ray photoelectron spectroscopy, Raman and Fourier transform infrared spectroscopy, which established that Tiron leads to the blending of chelating and bridging bidentate geometries for FT-nano-TiO2, whereas chromotropic acid produces bridging bidentate as well as monodentate geometries for FC-nano-TiO2. The surface chemistry of the studied membranes, polysulfone (Psf): FT-nano-TiO2 UF and Psf: FC-nano-TiO2 UF, was profoundly influenced by the benign distributions of the nanoadditives enriched with distinctly charged sites ([Formula: see text]), as evidenced by superior morphology, improved topography, enhanced surface hydrophilicity and altered electrokinetic features. The membranes exhibited enhanced solvent throughputs, viz. 3500-4000 and 3400-4300 LMD at 1 bar of transmembrane pressure, without significant compromise in their rejection attributes. The flux recovery ratios and fouling resistive behaviours of MMMs towards bovine serum albumin indicated that the nanoadditives could impart stable and appreciable antifouling activity, potentially aiding in a sustainable ultrafiltration performance.

Ring artifact correction in gamma-ray process tomography imaging.

Ring artifacts have been studied for X-ray based Computed Tomography (CT) systems but not on γ-ray based in-situ applications. This paper discusses application of recently proposed automatic ring artifact reduction method (Yoon et al., 2016) on previously obtained experimental projection data from a γ-ray based Industrial Process Tomography (IPT) system for a prototype catalytic column. Studies include qualitative and quantitative evaluation of the method. It is observed that ring artifacts are suppressed without loss of significant information in γ-ray PT images.

ZnO nanowire arrays: synthesis, optical and field emission properties.

Nanowire arrays of zinc oxide were synthesized on zinc foil by a simple thermal evaporation process. Morphologies and sizes of the synthesized nanostructures were varied by varying the reaction time and the surface roughness of the substrate. Self-catalytic liquid-solid mechanism was proposed for the growth of nanowires. ZnO nanostructures exhibited a strong UV emission at approximately 382 nm attributed to the band edge emission along with a defect related broad green emission at approximately 513 nm. These nanowire arrays exhibits good field emission property.

The electronic transport properties of ternary Cd(1-x)Zn(x)S nanowire networks.

We present the electronic transport characteristics of ternary alloy Cd(1-x)Zn(x)S nanowire networks in the dark and under white light illumination. Compared to the negligible dark current, we observed a photocurrent enhancement of up to four orders of magnitude at an intensity of 460 mW cm(-2). The time constant of the dynamic photoresponse is approximately 5 s. The current-voltage characteristics at different intensities show Ohmic behavior at low bias and space charge limited conduction (SCLC) at higher bias voltages. The SCLC behavior and slow time response indicate that the charge transport is dominated by tunneling at the percolating inter-nanowire junctions.

Ultra-small water-dispersible fluorescent chitosan nanoparticles: synthesis, characterization and specific targeting.

A robust water-in-oil microemulsion method of making water-dispersible ultra-small (<30 nm) size fluorescent chitosan nanoparticles is reported for the first time and specific targeting of these FCNPs to human leukemia cells via aptamer recognition is demonstrated.

Rapid synthesis of core/shell ZnS:Mn/Si nanotetrapods by a catalyst-free thermal evaporation route.

We report the fabrication of a hybrid all semiconductor core/shell nanotetrapod structure consisting of crystalline ZnS:Mn core and amorphous Si shell for the first time. The nanostructures were produced via a catalyst-free rapid thermal evaporation technique. Core/shell nanotetrapods were formed in two steps: (i) formation of the crystalline ZnS:Mn tetrapods and (ii) simultaneous surface adsorption of the in situ formed Si vapor species providing the amorphous shell. Crystalline tetrapod formation was guided by the formation of cubic structured ZnS octahedrons with four active (111) polar growth planes, which served as the favored growth site for the four wurtzite structured legs of the tetrapods. Choice of chloride salt as the source of dopant ion was crucial for the in situ generation of Si vapor. At elevated temperature, chloride salt reacted with the sulfur vapor to produce S2Cl2 gas that etched the Si wafers, generating Si vapor. Suppression of the surface-state-related blue emission was observed in the core/shell structures that clearly supported the formation of a shell layer. Elimination of the surface states ensured efficient energy transfer to the dopant Mn ionic state, resulting in the strong orange emission via (4)T(1)-(6)A(1) electronic transition.

ZnO hierarchical nanostructures: simple solvothermal synthesis and growth mechanism.

Hierarchical nano/micro structures of ZnO have been fabricated by solvothermal approach on sol-gel derived ZnO thin films. Paintbrush like nano/micro rod assembly, double-sided brush and windmill type architectures of ZnO are obtained when the ZnO thin film coated substrates were treated solvothermally in water at pH 10. Aligned nanorods are obtained at pH approximately 13.5 in water. In ethylenediamine-water solvent divergent micro/nanorod assemblies such as hemispherical dandelion, rice plant type bush of ZnO are obtained. Increase in the percentage of ethyelendiamine resulted in the formation of smaller assemblies of relatively thin nanorods. Initial slow reaction caused by the slow increase of the temperature inside the reaction medium and the different growth kinetics of the ZnO crystals are supposed to be the reason behind the architectural assemblies of the ZnO crystals.

A simple strategy for quantum dot assisted selective detection of cadmium ions.

Here we report a simple strategy for selective detection of cadmium ions by manipulating the electron transfer pathways of surface-engineered quantum dots.

Direct synthesis of ZnS nanoribbons, micro-sheets and tetrapods.

ZnS nano and micro structures such as nanoribbons, large sheets and tetrapod shaped crystals were fabricated by direct thermal evaporation of ZnS powder without using any catalyst. Formation of the one dimensional structures such as nanoribbons and micron order sheets was attributed to the vapor-solid growth mechanism. The formation of octahedron nucleus with cubic crystal structures was proposed as the growth unit of the wurtzite crystal structured tetrapods. Appearance of the periodic stacking faults or twining planes in between alternate cubic and hexagonal crystal structured zones along the growth direction of the ribbons provided secondary growth sites for the octahedron nucleus and subsequent crystal growth resulted in to the formation of the tetrapod arrays. These nano/micro structures of ZnS exhibited a green emission band at room temperature.

CdS:Mn nanorods: solvothermal synthesis and properties.

Manganese (0.05-9 mol.%) doped CdS nanorods were synthesized via solvothermal route using ethylenediamine (En) and a mixture of En and water as the solvents. The diameters and the lengths of the doped CdS nanorods varied from 40-100 nm and 600-2500 nm, respectively, with change in the composition of the solvents. The broad photoluminescence (PL) emission from the undoped CdS nanorods centered at approximately 535 nm is found to be blue shifted to 516 nm with the incorporation of Mn in the CdS crystal structure. Also increase in the intensity of the PL was noticed in the Mn doped CdS nanorods for both the solvent systems. Maximum PL intensity was observed for 1 mol.% Mn in case of En system and for 0.5 mol.% Mn in case of En/water system, above which quenching occurred as a result of Mn-Mn clustering. EPR study revealed six-line hyperfine splitting for low Mn concentration in both solvent systems. Increase in the Mn concentration caused EPR signal broadening due to Mn-Mn clustering.

Positron annihilation spectroscopic studies of solvothermally synthesized ZnO nanobipyramids and nanoparticles.

Zinc oxide (ZnO) samples in the form of hexagonal-based bipyramids and particles of nanometer dimensions were synthesized through solvothermal route and characterized by x-ray diffraction and transmission electron microscopy. Positron annihilation experiments were performed to study the structural defects such as vacancies and surfaces in these nanosystems. From coincidence Doppler broadening measurements, the positron trapping sites were identified as Zn vacancies or Zn-O-Zn trivacancy clusters. The positron lifetimes, their relative intensities, and the Doppler broadened lineshape parameter S all showed characteristic changes across the nanobipyramid size corresponding to the thermal diffusion length of positrons. In large nanobipyramids, vacancies within the crystallites also trapped positrons and the effects of agglomeration of such vacancies due to increased temperatures of synthesis were reflected in the variation of the annihilation parameters with their base diameters. The sizes of the nanoparticles used were all in the limit of thermal diffusion length of positrons and the annihilation characteristics were in accordance with the decreasing contribution from surfaces with increasing particle size.

Mn(2+)-induced substitutional structural changes in ZnS nanoparticles as observed from positron annihilation studies.

Zinc sulfide nanoparticles doped with different concentrations of manganese ions (Mn(2+)) were synthesized at various temperatures to investigate the effects of substitution and the associated defect evolution. Positron lifetime and Doppler broadening measurements were used as probes. The initial stage of defect recovery was dominated by the occupation of Zn(2+) vacancies by Mn(2+) ions, bringing in characteristic changes in the positron lifetimes, intensities and Doppler broadened lineshape parameters. Detailed analyses considering the presence of one and two types of defects were carried out to identify the type of defects which trap positrons at the different dopant concentrations. Electron paramagnetic resonance studies indicated increased Mn-Mn interaction and the formation of Mn clusters with further doping. The results are in striking contrast to those for nanorods, where vacancy recombination transformed their interior into regions free of defects.

Direct synthesis of ZnO nanowire arrays on Zn foil by a simple thermal evaporation process.

ZnO nanowire arrays were synthesized on zinc foil by a simple thermal evaporation process at relatively low temperature. Morphology and size controlled synthesis of the ZnO nanostructures was achieved by variation of the synthesis temperature, reaction time and the surface roughness of the substrate. A gas-solid and self-catalytic liquid-solid mechanism is proposed for the growth of nanowires at different temperatures. High-resolution transmission electron microscopy (HRTEM) showed that the as-grown nanowires were of single crystal hexagonal wurtzite structure, growing along the [101] direction. Photoluminescence exhibited strong UV emission at ∼382 nm and a broad green emission at ∼513 nm with 325 nm excitation. Raman spectroscopy revealed a phonon confinement effect when compared with results from bulk ZnO. The nanowire arrays also exhibited a field emission property.