Intrinsic Contamination Research Articles

Active Galactic Nuclei Selection and Demographics: A New Age with JWST/MIRI

Understanding the coevolution of supermassive black holes and their host systems requires a comprehensive census of active galactic nuclei (AGNs) behavior across a wide range of redshift, luminosity, obscuration level, and galaxy properties. We report significant progress with JWST toward this goal from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES). Based on comprehensive spectral energy distribution (SED) analysis of 3273 MIRI-detected sources, we identify 217 AGN candidates over a survey area of ∼34 arcmin2, including a primary sample of 111 AGNs in normal massive galaxies (M * > 109.5 M ☉) at z ∼ 0–4, an extended sample of 86 AGN candidates in low-mass galaxies (M * < 109.5 M ☉), and a high-z sample of 20 AGN candidates at z ∼ 4–8.4. Notably, about 80% of our MIRI-selected AGN candidates are new discoveries despite the extensive pre-JWST AGN searches. Even among the massive galaxies where the previous AGN search is believed to be thorough, 34% of the MIRI AGN identifications are new, highlighting the impact of obscuration on previous selections. By combining our results with the efforts at other wavelengths, we build the most complete AGN sample to date and examine the relative performance of different selection techniques. We find the obscured AGN fraction increases from L AGN,bol ∼ 1010 L ⊙ to 1011 L ⊙ and then drops toward higher luminosity. Additionally, the obscured AGN fraction gradually increases from z ∼ 0 to z ∼ 4 with most high-z AGNs obscured. We discuss how AGN obscuration, intrinsic SED variations, galaxy contamination, survey depth, and selection techniques complicate the construction of a complete AGN sample.

Challenges and mitigation strategies associated with Burkholderia cepacia complex contamination in pharmaceutical manufacturing.

Burkholderia cepacia complex (BCC) is a Gram-negative, non-spore-forming bacterium with more than 20 opportunistic pathogenic species, most commonly found in soil and water. Due to their rapid mutation rates, these organisms are adaptable and possess high genomic plasticity. BCC can cause life-threatening infections in immunocompromised individuals, such as those with cystic fibrosis, chronic granulomatous disease, and neonates. BCC contamination is a significant concern in pharmaceutical manufacturing, frequently causing non-sterile product recalls. BCC has been found in purified water, cosmetics, household items, and even ultrasound gel used in veterinary practices. Pharmaceuticals, personal care products, and cleaning solutions have been implicated in numerous outbreaks worldwide, highlighting the risks associated with intrinsic manufacturing site contamination. Regulatory compliance, product safety, and human health protection depend on testing for BCC in pharmaceutical manufacturing. Identification challenges exist, with BCC often misidentified as other bacteria like non-lactose fermenting Escherichia coli or Pseudomonas spp., particularly in developing countries where reporting BCC in pharmaceuticals remains limited. This review comprehensively aims to address the organisms causing BCC contamination, genetic diversity, identification challenges, regulatory requirements, and mitigation strategies. Recommendations are proposed to aid pharmaceutical chemists in managing BCC-associated risks and implementing prevention strategies within manufacturing processes.

Beyond acceptable limits: intrinsic contamination in commercial 15N2 impedes reliable N2 reduction experiments

The validity of N2 reduction experiments relies on control experiments with isotopically labelled 15N2. Commercially obtained 15N2 contains high amounts of 15NH3 and other activated nitrogen species which are readily reduced to 15NH3.

Law matters - assessment of country-level code implementation and sales of breastmilk substitutes in South Asia.

This study examines the status of implementation of the International Code of Marketing of Breast-milk Substitutes of eight countries in the South Asia region (Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka), and describes the sales value and volume of commercial milk formula (CMF) marketed as breastmilk substitutes (BMS) and baby food in four countries (Bangladesh, India, Pakistan, and Sri Lanka). A mix of descriptive methods is used to assess national status of Code implementation, including a desk review of the 2022 WHO/UNICEF/IBFAN Code Status Report, systematic content analysis of national Code measures, and insights generated from the participation of key government and UNICEF/WHO actors in a regional workshop that aimed to identify each country's barriers, gaps, and the status of Code implementation. Data on the sales value and volume of CMF and baby food between 2007 to 2021 and with the prediction to 2026 in Bangladesh, India, Pakistan, and Sri Lanka were obtained from Global Data. There are major gaps in Code implementation in countries even with legal measures considered substantially aligned with the Code, such as the inadequate age range of CMF covered in the scope, insufficient safeguards against conflicts of interest in the health system, lack of warning of risks of intrinsic contamination of powdered milk formula, and an absence of effective monitoring and enforcement mechanisms. Data on CMF sales shows health facilities and pharmacies sustain the highest sales. Lower sales volume of infant formula (including special formula), compared to other CMF such as follow-up formula and growing-up milk, has been observed in three of the four countries (Bangladesh, India, and Sri Lanka). Overall, GUM, followed by baby cereals, accounted for a large portion of CMF and baby foods sales in the same three countries. (1) Closing the gaps between national measures and the Code, (2) Ensuring effective monitoring and enforcement mechanisms, (3) Strengthening conflicts of interest safeguards in the health system, (4) Tackling digital marketing, and (5) Galvanizing political support and support from in-country public health and women's rights jurist networks.

Measurement of the intrinsic hadronic contamination in the NA64[formula omitted] high-purity [formula omitted] beam at CERN

We present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c. The analysis, performed using data collected by the NA64-e experiment in 2022, is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64 detector. We determined the contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those from a dedicated setup, in which only hadrons impinged on the detector. We also obtained an estimate of the relative protons, anti-protons and pions yield by exploiting the different absorption probabilities of these particles in matter. We cross-checked our results with a dedicated Monte Carlo simulation for the hadron production at the primary T2 target, finding a good agreement with the experimental measurements.

Multi-Contaminant Getter for Trace Airborne Contaminant Capture in Elevated Temperature Electrochemical Systems

Electrochemical systems operating at elevated temperatures such as solid oxide fuel cells (SOFC), solid oxide electrolysis cells (SOEC) and oxygen transport membranes (OTM) are susceptible to electrochemical performance degradation due to the presence of intrinsic and extrinsic contaminants in air stream. Intrinsic and extrinsic airborne contaminants include a wide range of gaseous compounds consisting of cations such as Cr, Si, and B, intrinsic impurities include SOx, NOx, VOC and PM’s. During high temperature exposure, the contaminants deposit and react with the cell components leading to both ohmic and non-ohmic polarization buildup. The use of a cost-effective, design-agnostic, passive “getter” system has been proposed for capturing trace contaminants. A number of getter formulations (containing alkaline earth, transition metal and lanthanide group elements) have been synthesized and experimentally tested. Results will be presented.

Background suppression in the COSINUS experiment: Active muon veto and radiopure materials selection

For over twenty-five years the DAMA/LIBRA experiment has reported an annual modulation signal that is consistent with a dark matter explanation. This signal is, currently, in tension with the null results observed by other searches that utilize different target detectors. The COSINUS experiment will perform a model-independent cross-check of the DAMA/LIBRA result by using the same target material, NaI crystals, operated as scintillating calorimeters. By measuring both temperature and light the NaI crystals in COSINUS will be able to distinguish between electron and nuclear recoils on an event-by-event basis. However, background events induced by cosmic-rays, environmental radioactivity or the intrinsic contamination of the materials used in the crystal, shielding and infrastructure can pose an issue to any analysis and must be fully understood. We report on the status of the development of the simulation for an active water Cherenkov muon veto, as well as the results of the beginning radiogenic material screening.

Bacterial Contamination of Antiseptics, Disinfectants and Hand Hygiene Products in Healthcare Facilities in High-Income Countries: A Scoping Review

This scoping review addresses bacterial contamination of antiseptics, low-level disinfectants, and hand hygiene products in healthcare settings in high-income countries. Over 70 years, 114 articles were found: 68 outbreaks, 13 pseudo-outbreaks and 33 cross-sectional surveys. Outbreaks affected median 29 (1–151) patients, extended for 26 (1–156) weeks and had a case fatality of 0.0% (0.0–60.0%). Most (72.8%) (pseudo-)outbreaks were caused by water-based chlorhexidine (CHG), quaternary ammonium compounds (QUAT) and the combination CHG–QUAT. Contaminating bacteria were nonfermentative Gram-negative rods (87.6% (pseudo-)outbreaks), mainly Burkholderia cepacia, Pseudomonas aeruginosa and Achromobacter spp.) and Enterobacterales (29.6%, 24/81), mostly Serratia spp.). Risk factors were at the level of the bacteria (natural resistance to CHG and QUAT), containers (design and functioning, presence of cork and cotton, biofilm formation), preparation (nonsterile water, overdilution) and practices (too long expiry dates, inappropriate container reprocessing, topping up of containers and deviation from procedures). Transmission occurred through direct contact (antiseptics), contact with semicritical items (disinfectants) and were handborne (soaps). During recent decades, reports of soap contaminated with Enterobacterales emerged and nationwide outbreaks of intrinsically contaminated CHG occurred. Outstanding issues comprise intrinsic contamination, implementation of antiseptic stewardship, the role of unit doses and sterile products, transmission studies, biofilm control and understanding healthcare providers’ perceptions.

A study on the occurrence of Burkholderia cepacia complex in ultrasound gels used in different veterinary clinical settings in India.

Burkholderia cepacia complex (Bcc) organisms are emerging multidrug-resistant pathogens. They are opportunistic and cause severe diseases in humans that may result in fatal outcomes. They are mainly reported as nosocomial pathogens, and transmission often occurs through contaminated pharmaceutical products. From 1993 to 2019, 14 Bcc outbreaks caused by contaminated ultrasound gels (USGs) have been reported in several countries, including India. We screened a total of 63 samples of USGs from various veterinary and human clinical care centers across 17 states of India and isolated 32 Bcc strains of Burkholderia cenocepacia (46.8%), B. cepacia (31.3%), B. pseudomultivorans (18.8%) and B. contaminans (3.1%) species. Some isolates were co-existent in a single ultrasound gel sample. The isolation from unopened gel bottles revealed the intrinsic contamination from manufacturing sites. The MALDI-TOF analysis to identify the Bcc at the species level was supported by the partial sequencing of the recA gene for accurate species identification. The phylogenetic analysis revealed that isolates shared clades with human clinical isolates, which is an important situation because of the possible infections of Bcc by USGs both in humans and animals. The pulsed field gel electrophoresis (PFGE) typing identified the genetic variation among the Bcc isolates present in the USGs. The findings indicated USGs as the potential source of Bcc species.

Identification of radiopure tungsten for low background applications

In this article we explore the availability of radiopure tungsten and its potential as high density shield material for low background applications. For compact shield designs, conventionally, lead is used. Metallic tungsten and tungsten pseudo-alloys reach higher densities up to 19.3 g cm−3 and do not exhibit a significant 210Pb activity, which is a typical intrinsic contamination in lead. Within several γ-ray screening campaigns we were able to identify tungsten samples with activities similar or better than 1 mBq kg−1 in 232Th, 40K, 60Co and the second part of the 238U decay chain. In cooperation with a manufacturer we further reduced a persisting contamination in the first part of the 238U decay chain by a factor of ∼2.5 down to (305 ± 30) mBq kg−1. With Monte Carlo simulations, the construction of prototype tungsten-based setups and dedicated measurements, the shield capability of tungsten in comparison to lead was extensively studied. Specifically, the impact of cosmogenic radiation on the background at shallow depth was investigated. We showed that a 6%–40% reduction (depending on the exact shield configuration) in the muon-induced neutron fluence is achievable by replacing lead with an equivalent amount of tungsten regarding the suppression of external γ-radiation. Overall, many benefits using tungsten especially for low energy applications below a few 100 keV are found. The pseudo-tungsten alloy presented in this work paves the way for several applications especially regarding background suppression in particle and astroparticle physics search programs.

Simulation-based design study for the passive shielding of the COSINUS dark matter experiment

The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment aims at the detection of dark matter-induced recoils in sodium iodide (NaI) crystals operated as scintillating cryogenic calorimeters. The detection of both scintillation light and phonons allows performing an event-by-event signal to background discrimination, thus enhancing the sensitivity of the experiment. The choice of using NaI crystals is motivated by the goal of probing the long-standing DAMA/LIBRA results using the same target material. The construction of the experimental facility is foreseen to start by 2021 at the INFN Gran Sasso National Laboratory (LNGS) in Italy. It consists of a cryostat housing the target crystals shielded from the external radioactivity by a water tank acting, at the same time, as an active veto against cosmic ray-induced events. Taking into account both environmental radioactivity and intrinsic contamination of materials used for cryostat, shielding and infrastructure, we performed a careful background budget estimation. The goal is to evaluate the number of events that could mimic or interfere with signal detection while optimising the geometry of the experimental setup. In this paper we present the results of the detailed Monte Carlo simulations we performed, together with the final design of the setup that minimises the residual amount of background particles reaching the detector volume.

Hydrophilic, Clean Graphene for Cell Culture and Cryo-EM Imaging.

The wettability of graphene is critical for numerous applications but is very sensitive to its surface cleanness. Herein, by clarifying the impact of intrinsic contamination, i.e., amorphous carbon, which is formed on the graphene surface during the high-temperature chemical vapor deposition (CVD) process, the hydrophilic nature of clean graphene grown on single-crystal Cu(111) substrate was confirmed by both experimental and theoretical studies, with an average water contact angle of ∼23°. Furthermore, the wettability of as-transferred graphene was proven to be highly dependent on its intrinsic cleanness, because of which the hydrophilic, clean graphene exhibited improved performance when utilized for cell culture and cryoelectron microscopy imaging. This work not only validates the intrinsic hydrophilic nature of graphene but also provides a new insight in developing advanced bioapplications using CVD-grown clean graphene films.

Neutrinoless Double Beta Decay with Germanium Detectors: 1026 yr and Beyond

In the global landscape of neutrinoless double beta (0νββ) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the 76Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive 0νββ decay search. The Majorana and Gerda experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of 2.53 ± 0.08 keV at the Qββ and an unprecedented low background level of 5.2×10−4 cts/(keV·kg·yr), respectively. In this paper, we will review the path of 0νββ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the Gerda experiment setting a limit on the half-life of 76Ge 0νββ decay at T1/2&gt;1.8×1026 yr (90% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to 1028 yr and beyond, opening the way to the exploration of the normal ordering region.

Herbal Nephropathy.

An estimated one-third of adults in developed countries and more than 80% of the population in many low- and middle-income countries use herbal and traditional medicines to promote health or for the treatment of common diseases. Herbal medicines can cause kidney damage as a result of intrinsic toxicity, adulteration, contamination, replacement, misidentification, mistaken labeling, and unfavorable herb-drug interactions. The kidneys, due to their high blood flow rate, large endothelial surface area, high metabolic activity, active uptake by tubular cells, medullary interstitial concentration, and low urine pH are particularly vulnerable to development of toxic injury in the form of different syndromes like acute kidney injury, nephrolithiasis, chronic interstitial fibrosis, or uroepithelial cancer. Herbal medicines can also cause crystalluria or hypertension and some could increase potassium blood levels in patients with kidney damage. It is of critical importance that health care organizations around the world regulate herbal and traditional remedies in order to reduce the risk of herb-toxic acute kidney injury or chronic kidney disease. The nephrologist must be aware of the potential nephrotoxicity from herbal medicine and supplements. A careful history and specific questioning about use of herbal medicines use is essential.

Occurrence and Fate of Bisphenol A and its Congeners in Two Wastewater Treatment Plants and Receiving Surface Waters in Romania.

The present study investigated the distribution and environmental fate of Bisphenol A (BPA), the 4-hydroxyacetophenone (4-HAP) metabolite, and 5 other bisphenol congeners in 2 municipal wastewater treatment plants (WWTPs) and their receiving rivers in Romania. Accordingly, a new, highly sensitive and accurate solid-phase extraction-liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated. This technique generated low limit of quantitation values: below 2.3 ng/L for surface water and less than 2.4 and 2.7 ng/L for WWTP effluent and influent water. The sum of detected analytes in wastewater was between 1337 and 16 118 ng/L for influent samples and between 15 and 96 ng/L for effluent samples. In surface water, the total of all compounds was somewhere between 34 and 240 ng/L. The highest concentration observed was for BPA in all 3 types of analyzed water (up to 9140 ng/L for influent, as high as 75 ng/L for effluent, and a maximum of 135 ng/L in surface waters). All analyzed samples were free of bisphenols B, C, and F. For all analytes detected in surface water, the concentration values were higher than those determined in the effluent samples, which may be caused by intrinsic contamination of the 2 rivers (Danube and Jiu Rivers). Values of environmental risk coefficients, calculated for both effluents and surface waters, indicated a low ecological risk or no ecological risk for 3 types of organisms (algae, daphnia, and fish). Human risk assessment calculation suggests no risk to human health as a result of the presence of BPA in either of the 2 rivers. Environ Toxicol Chem 2021;40:435-446. © 2020 SETAC.

Sensitivity to neutrinos from the solar CNO cycle in Borexino

Neutrinos emitted in the carbon, nitrogen, oxygen (CNO) fusion cycle in the Sun are a sub-dominant, yet crucial component of solar neutrinos whose flux has not been measured yet. The Borexino experiment at the Laboratori Nazionali del Gran Sasso (Italy) has a unique opportunity to detect them directly thanks to the detector’s radiopurity and the precise understanding of the detector backgrounds. We discuss the sensitivity of Borexino to CNO neutrinos, which is based on the strategies we adopted to constrain the rates of the two most relevant background sources, pep neutrinos from the solar pp-chain and ^{210}Bi beta decays originating in the intrinsic contamination of the liquid scintillator with ^{210}Pb. Assuming the CNO flux predicted by the high-metallicity Standard Solar Model and an exposure of 1000 days times 71.3 t, Borexino has a median sensitivity to CNO neutrino higher than 3 sigma . With the same hypothesis the expected experimental uncertainty on the CNO neutrino flux is 23%, provided the uncertainty on the independent estimate of the ^{210}text {Bi} interaction rate is 1.5 hbox {cpd}/100~hbox {ton} . Finally, we evaluated the expected uncertainty of the C and N abundances and the expected discrimination significance between the high and low metallicity Standard Solar Models (HZ and LZ) with future more precise measurement of the CNO solar neutrino flux.

Detection of Possible Medical Product-Related Infection or Pathogen Transmission—United States, 2015–2019

Background: Medications, medical devices, biological products, and other medical products can cause healthcare-associated infections related to contamination in production or transportation (intrinsic contamination) or contamination at the point of use (extrinsic contamination). Rapid identification of contaminated medical products can lead to actions to decrease further patient harm. We sought to describe events that prompted public health investigations of contaminated medical products in healthcare facilities. Methods: We reviewed records of CDC consultations with health departments and healthcare facilities from January 2015 through August 2019 to identify public health investigations in which medical products were identified as a likely source of patient infection or pathogen transmission to at least 1 patient. We collected data on products, contamination type, pathogens, route of patient exposure, healthcare setting where exposure occurred, and resulting actions. Results: There were 34 investigations involving medications (n = 15, 44%), medical devices (n = 12, 35%), biological products (n = 3, 9%), and other medical products (n = 4, 12%). Intrinsic contamination was suspected in 15 investigations (44%), with 13 (87%) based on isolation of a pathogen from unopened products and 2 (13%) based on isolation of similar pathogens from patients in contact with a medical product at multiple facilities. Extrinsic contamination was suspected in 19 investigations (56%) based on evidence of pathogen transmission at a single healthcare facility and concurrent infection control gaps at that facility supporting a mechanism of contamination. The most common pathogens prompting investigation were nontuberculous mycobacteria (n = 9, 26%), Burkholderia spp (n = 7, 21%), Klebsiella spp (n = 3, 9%), Serratia spp (n = 2, 6%), and other environmental and commensal organisms. Patients were most commonly exposed in hospitals (n = 19, 56%) and outpatient settings (n = 9, 26%). The most common patient exposures that resulted in transmission of the pathogen were infusions and injections (n = 15, 44%), diagnostic and therapeutic procedures (n = 9, 26%), and surgery (n = 5, 15%). Patient were notified and offered testing in at least 6 investigations (18%) . Interventions included product removal, healthcare provider alerts, patient notification and testing, modification of injection safety practices and other general infection control practices, correction of improper storage and handling, and changes in product design, manufacturing processes, or instructions for use. Conclusions: Public health investigations identified intrinsic and extrinsic contamination of medications, devices, and other products as a cause of healthcare-associated infections. Healthcare facilities should consider contaminated products in investigations of healthcare-associated infections, take steps to identify local infection control concerns, and alert public health authorities to events that could suggest widespread contamination.Funding: NoneDisclosures: None

Investigation of Events Related to Laboratory-Confirmed Contamination of Pharmaceutical Products: Summary of CDC Consultation

Background: Contaminated pharmaceutical products pose serious infection risks to patients and can lead to significant morbidity and mortality. Contamination at the point of manufacturing or compounding (intrinsic contamination) has the potential to affect large numbers of patients. Public health plays a critical role in detecting and investigating such events. We identified investigations involving intrinsically contaminated pharmaceuticals to characterize the burden and scope of harm associated with these events. Methods: We reviewed Centers for Disease Control and Prevention records to identify US investigations between January 1, 2009, and December 31, 2018, involving laboratory-confirmed contamination of manufactured medications and pharmacy-compounded preparations (P-CPs), using relevant search terms (eg, “medication contamination”). Laboratory confirmation was defined as identification of a pathogen from a manufactured medication or P-CP. We determined the number and type of patient infections associated with these investigations, the number of states involved, pathogens identified, type of medication (sterile or nonsterile), route of administration, and how the contamination event was first identified. We excluded investigations when the mode of production was unknown. Results: We identified 20 investigations in at least 20 states involving laboratory-confirmed contamination of manufactured medications (n = 12) and P-CPs (n = 8). Patient infections were identified in 16 (80%) investigations (9 involving manufactured medications and 7 involving P-CPs) resulting in at least 1,183 infections and at least 73 deaths. Bloodstream infections were the most common infection type (n = 7, 44%). Waterborne pathogens (eg, Serratia marcescens, Burkholderia cepacia) were cultured from medications in 83% (n = 10) of investigations involving manufactured medications and 75% (n = 6) of investigations involving P-CPs. Contamination of sterile pharmaceutical products occurred in 14 (70%) investigations; 11 (79%) of these involved injectables. Information regarding how contaminated pharmaceuticals were first identified was documented for 18 investigations; most cases (n = 14, 78%) started with investigation of patient infections by facilities, public health, or both, which led to laboratory testing of pharmaceuticals and confirmation of contamination. Conclusions: The events summarized here likely underestimate the frequency of intrinsic contamination of pharmaceutical products in the United States. These events can have devastating consequences that impact patients across the country. Waterborne pathogens appear to be the most frequently identified source of contamination in both manufactured medications and P-CPs.Detection, investigation, control, and prevention of pharmaceutical contamination events benefit from collaboration between state and federal public health authorities; without public health intervention. Such contamination may have gone undetected and could have harmed additional patients.Funding: NoneDisclosures: None

High-Intensity Laser-Driven Oxygen Source from CW Laser-Heated Titanium Tape Targets

The interaction of high-intensity laser pulses with solid targets can be used as a highly charged, energetic heavy ion source. Normally, intrinsic contaminants on the target surface suppress the performance of heavy ion acceleration from a high-intensity laser–target interaction, resulting in preferential proton acceleration. Here, we demonstrate that CW laser heating of 5 µm titanium tape targets can remove contaminant hydrocarbons in order to expose a thin oxide layer on the metal surface, ideal for the generation of energetic oxygen beams. This is demonstrated by irradiating the heated targets with a PW class high-power laser at an intensity of 5 × 1021 W/cm2, showing enhanced acceleration of oxygen ions with a non-thermal-like distribution. Our new scheme using a CW laser-heated Ti tape target is promising for use as a moderate repetition energetic oxygen ion source for future applications.

New Growth Frontier: Superclean Graphene.

The last 10 years have witnessed significant progress in chemical vapor deposition (CVD) growth of graphene films. However, major hurdles remain in achieving the excellent quality and scalability of CVD graphene needed for industrial production and applications. Early efforts were mainly focused on increasing the single-crystalline domain size, large-area uniformity, growth rate, and controllability of layer thickness and on decreasing the defect concentrations. An important recent advance was the discovery of the inevitable contamination phenomenon of CVD graphene film during high-temperature growth processes and the superclean growth technique, which is closely related to the surface defects and to the peeling-off and transfer quality. Superclean graphene represents a new frontier in CVD graphene research. In this Perspective, we aim to provide comprehensive understanding of the intrinsic growth contamination and the experimental solution of making superclean graphene and to provide an outlook for future commercial production of high-quality CVD graphene films.