Synthesis and characterization of TiO2-based supported materials for industrial application and recovery in a pilot photocatalytic plant using chemometric approach.

In this contribution, the performance of powdered titanium dioxide (TiO2)-based photocatalysts was evaluated in a pilot photocatalytic plant for the degradation of different dyes, with an investigated volume of 1 L and solar simulated light as irradiation source. Five different samples, synthesized in our laboratories, were tested in the pilot plant, each consisting of TiO2 nanoparticles (NPs) coupled with a different material (persistent luminescent material and semiconductor material) and treated in different thermal conditions. All synthesized samples have been subjected to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller analysis (BET), and transmission electron microscopy (TEM) characterization, to shed light on the influence of introducing other materials on titania characteristics. To study and evaluate the significance of the parameters affecting the process in the pilot plant, a chemometric approach was applied, by selecting a mathematical model (D-Optimal) to simultaneously monitor a large number of variables (i.e., 7), both qualitative and quantitative, over a wide range of levels. At the same time, the recovery of the synthesized photocatalysts was studied following a novel promising recuperation method, i.e., annulling the surface charge of the suspended samples by reaching the isoelectric point (pHPZC) of each sample, for the quantitative precipitation of TiO2 nanoparticles.

MicroRaman spectroscopy detects the presence of microplastics in human urine and kidney tissue.

There is a growing concern within the medical community about the potential burden of microplastics on human organs and tissues. In this study, we investigated by microRaman spectroscopy the presence of microplastics in human kidneys and urine. Moreover, an open-access software was developed and validated for the project, which enabled the comparison between the investigated spectra and a self-created spectral database, thus enhancing the ability to characterize polymers and pigments in biological matrices. Healthy portions of ten kidneys obtained from nephrectomies, as well as ten urine samples from healthy donors were analyzed: 26 particles in both kidney and urine samples were identified, with sizes ranging from 3 to 13 µm in urine and from 1 to 29 µm in kidneys. The most frequently determined polymers are polyethylene and polystyrene, while the most common pigments are hematite and Cu-phthalocyanine. This preclinical study proves the presence of microplastics in renal tissues and confirms their presence in urine, providing the first evidence of kidney microplastics deposition in humans.

Antibacterial and Photocatalytic Activities of LDH-Based Sorbents of Different Compositions.

Layered double hydroxides (LDHs) play a fundamental role in the processes for the abatement of pollutants in water, with reference to heavy metal decontamination. The research on the topic is multiobjective target oriented, aiming at combining environmental remediation with the possibility of reusing a sorbent as many times as possible, turning it into a renewable resource. In this study, the antibacterial and catalytic properties of a ZnAl-SO4 LDH and its resulting product after being subjected to a Cr(VI) remediation process are compared. Both solid substrates have also been tested after undergoing a thermal annealing process. The sorbent (previously described and tested for remediation) has been investigated for its antibacterial activity in view of further surgery and drug delivery applications. Finally, its photocatalytic properties have been experimentally tested in the degradation of a model pollutant, i.e., Methyl Orange (MO), under solar-simulated light. Identifying the best recycling strategy for these materials requires an accurate knowledge of their physicochemical properties. The results show that both the antimicrobial activity and the photocatalytic performance may considerably improve after thermal annealing.

Inversions of landslide strength as a proxy for subsurface weathering.

Distributions of landslide size are hypothesized to reflect hillslope strength, and consequently weathering patterns. However, the association of weathering and critical zone architecture with mechanical strength properties of parent rock and soil are poorly-constrained. Here we use three-dimensional stability to analyze 7330 landslides in western Oregon to infer combinations of strength - friction angles and cohesion - through analysis of both failed and reconstructed landslide terrain. Under a range of conditions, our results demonstrate that the failure envelope that relates shear strength and normal stress in landslide terrain is nonlinear owing to an exchange in strength with landslide thickness. Despite the variability in material strength at large scales, the observed gradient in proportional cohesive strength with landslide thickness may serve as a proxy for subsurface weathering. We posit that the observed relationships between strength and landslide thickness are associated with the coalescence of zones of low shear strength driven by fractures and weathering, which constitutes a first-order control on the mechanical behavior of underlying soil and rock mass.

Electrospun alginate mats embedding silver nanoparticles with bioactive properties.

Polysaccharide-based composites embedding silver nanoparticles (AgNPs) represent a promising alternative to common antimicrobial materials because of the effective, broad-spectrum biocidal properties of AgNPs combined with the biocompatibility and environmental safety of the naturally occurring polymeric component. In this work, AgNPs stabilized with alginate chains (Alg@AgNPs) were successfully synthesized in situ within the polysaccharide solution through a wet chemical approach carried out at different concentrations of the silver salt precursor. Once obtained, the aqueous suspensions were electrospun to prepare non-woven membranes, showing a homogeneous nanostructured texture (with fiber diameter between 100 and 150 nm), which was found to be influenced by the size (between 20 and 35 nm) of the embedded metal nanoparticles. The biocidal potential of the nanocomposite mats was preliminarily tested against Gram-negative E. coli. The results showed that the antimicrobial response of the investigated samples occurred within a day of incubation and can be observed for AgNPs content in the polysaccharide fibers far below the nanomolar regime.

Comparison of Different Commercial Nanopolystyrenes: Behavior in Exposure Media, Effects on Immune Function and Early Larval Development in the Model Bivalve Mytilus galloprovincialis.

In the absence of standard methods for the detection/quantification of nanoplastics (NPs) in environmental samples, commercial nanopolymers are utilized as proxies for toxicity testing and environmental risk assessment. In marine species, a considerable amount of data are now available on the effects of nanopolystyrene (PS-NPs) of different size/surface characteristics. In this work, amino modified PS-NPs (PS-NH2) (50 and 100 nm), purchased from two different companies, were compared in terms of behavior in exposure media and of biological responses, from molecular to organism level, in the model marine bivalve Mytilus. Different PS-NH2 showed distinct agglomeration and surface charge in artificial sea water (ASW) and hemolymph serum (HS). Differences in behavior were largely reflected by the effects on immune function in vitro and in vivo and on early larval development. Stronger effects were generally observed with PS-NH2 of smaller size, showing less agglomeration and higher positive charge in exposure media. Specific molecular interactions with HS components were investigated by the isolation and characterization of the NP-corona proteins. Data obtained in larvae demonstrate interference with the molecular mechanisms of shell biogenesis. Overall, different PS-NH2 can affect the key physiological functions of mussels at environmental concentrations (10 µg/L). However, detailed information on the commercial NPs utilized is required to compare their biological effects among laboratory experiments.

Effect of sodium alginate molecular structure on electrospun membrane cell adhesion.

Alginate-based electrospun nanofibers prepared via electrospinning technique represent a class of materials with promising applications in the biomedical and pharmaceutical industries. However, to date, the effect of alginate molecular mass and block composition on the biological response of such systems remains to some extent unclear. As such, in the present work, three alginates (i.e., M.pyr, L.hyp, A.nod) with different molecular features are employed to prepare nanofibers whose ability to promote cell adhesion is explored by using both skin and bone cell lines. Initially, a preliminary investigation of the raw materials is carried out via rheological and zeta-potential measurements to determine the different grade of polyelectrolyte behaviour of the alginate samples. Specifically, both the molecular mass and block composition are found to be important factors affecting the alginate response, with long chains and a predominance of guluronic moieties leading to a marked polyelectrolyte nature (i.e., lower dependence of the solution viscosity upon the polymer concentration). Subsequently, physically crosslinked alginate nanofibrous mats are first morphologically characterized via both scanning electron and atomic force microscopy, which show a homogenous and defect-free structure, and their biological response is then evaluated. Noticeably, fibroblast and keratinocyte cell lines do not show significant differences in terms of cell adhesion on the three mats (i.e., 30-40% and 10-20% with respect to the seeded cells, respectively), with the formers presenting a greater affinity toward the alginate-based nanofibers. Conversely, both the investigated osteoblast cells are characterized by a distinct behaviour depending on the alginate type. Specifically, polysaccharide samples with an evident polyelectrolyte nature are found to better promote cell viability (i.e., cell adhesion in the range 15-36% with respect to seeded cells) compared to the ones displaying a nearly neutral behaviour (i.e., cell adhesion in the range 5-25% with respect to seeded cells). Therefore, the obtained results, despite being preliminary, suggest that the alginate type (i.e., molecular structure properties) may play a topical role in conditioning the efficiency of healing patches for bone reparation, but it has a negligible effect in the case of skin regeneration.

Effects of distancing and pattern of breathing on the filtering capability of commercial and custom-made facial masks: An in-vitro study.

BACKGROUND: Since the beginning of the COVID-19 pandemics, masking policies have been advocated. While masks are known to prevent transmission towards other individuals, it is unclear if different types of facial masks can protect the user from inhalation. The present study compares in-vitro different commercial and custom-made facial masks at different distances and breathing patterns. METHODS: Masks were placed on a head mannequin connected to a lung simulator, using a collecting filter placed after the mannequin airway. Certified, commercial and custom-made masks were tested at three different distances between the emitter and the mannequin: 40 cm, 80 cm and 120 cm. Two patterns of breathing were used, simulating normal and polypneic respiration. A solution of methylene blue was nebulized with a jet nebulizer and different mask-distance-breathing pattern combinations were tested. The primary endpoint was the inhaled fraction, defined as the amount of methylene blue detected with spectrophotometry expressed as percent of the amount detected in a reference condition of zero distance and no mask. FINDINGS: We observed a significant effect of distance (p < 0.001), pattern of breathing (p = 0.040) and type of mask (p < 0.001) on inhaled fraction. All masks resulted in lower inhaled fraction compared to breathing without mask (p < 0.001 in all comparisons), ranging from 41.1% ± 0.3% obtained with a cotton mask at 40 cm distance with polypneic pattern to <1% for certified FFP3 and the combination of FFP2 + surgical mask at all distances and both breathing pattern conditions. DISCUSSION: Distance, type of device and breathing pattern resulted in highly variable inhaled fraction. While the use of all types of masks resulted relevantly less inhalation compared to distancing alone, only high-grade certified devices (FFP3 and the combination of FFP2 + surgical mask) ensured negligible inhaled fraction in all conditions.

Functional and Morphological Changes Induced in Mytilus Hemocytes by Selected Nanoparticles.

Nanoparticles (NPs) show various properties depending on their composition, size, and surface coating, which shape their interactions with biological systems. In particular, NPs have been shown to interact with immune cells, that represent a sensitive surveillance system of external and internal stimuli. In this light, in vitro models represent useful tools for investigating nano-bio-interactions in immune cells of different organisms, including invertebrates. In this work, the effects of selected types of NPs with different core composition, size and functionalization (custom-made PVP-AuNP and commercial nanopolystyrenes PS-NH2 and PS-COOH) were investigated in the hemocytes of the marine bivalve Mytilus galloprovincialis. The role of exposure medium was evaluated using either artificial seawater (ASW) or hemolymph serum (HS). Hemocyte morphology was investigated by scanning electron microscopy (SEM) and different functional parameters (lysosomal membrane stability, phagocytosis, and lysozyme release) were evaluated. The results show distinct morphological and functional changes induced in mussel hemocytes depending on the NP type and exposure medium. Mussel hemocytes may represent a powerful alternative in vitro model for a rapid pre-screening strategy for NPs, whose utilization will contribute to the understanding of the possible impact of environmental exposure to NPs in marine invertebrates.

UV-254 degradation of nicotine in natural waters and leachates produced from cigarette butts and heat-not-burn tobacco products.

Nicotine is an important emerging contaminant widely detected in water resources. The main nicotine sources are human excretions from users and leaching from discarded tobacco product waste, which represents the most commonly littered item in urban areas and coasts. In this study, the UV254 photolytical fate of nicotine in natural water and leachates produced from conventional cigarettes (CCs) and the new generation heat-not-burn (HnBs) tobacco products is examined for the first time. The effect of UV254 irradiation on nicotine depletion in ultrapure water was initially studied. The reaction was pseudo first-order with respect to nicotine concentration at low concentrations and shifted to lower order at higher concentrations, an effect associated to absorption saturation. Although nicotine removal was fast, only 9.5% of the total organic carbon was removed after irradiation due to the formation of by-products. The chemical structures of six photo-products were derived by means of liquid and gas chromatography coupled to mass spectrometry. The photodegradation kinetics was found to depend on pH and faster kinetics were recorded when the monoprotonated form of nicotine was dominant (pH = 5-8). The presence of humic acids was found to slightly delay kinetics as they competed with nicotine for lamp irradiance, whereas the presence of salt had no effect on the direct photolysis of nicotine. Direct photolysis studies were also performed using natural waters. Compared to ultra-pure water, photodegradation was found to proceed slightly slower in river water, in similar kinetics in seawater, and relatively faster in rain water. The later was assumed to be due to the lower pH compared to the rest of the natural water tested. Leachates from used HnBs and smoked CCs were also submitted to UV254 irradiation and direct photolysis was found to proceed fast despite the high complexity of these matrices. Nonetheless, the total organic carbon in the system remained the same after irradiation due to the abundance of organics and photo-products formed. We take advantage of the present investigations and report the leaching behavior of nicotine from HnBs and CCs. Among others, we found that in HnBs ~70% of the total and bioavailable nicotine content remains in the tobacco sticks after operation and this percentage drops to 15% in CCs due to the reduction in mass after smoking. This finding demonstrated the importance of properly disposing tobacco product waste to prevent nicotine leaching in water bodies.

Systematic Study on TiO2 Crystallization via Hydrothermal Synthesis in the Presence of Different Ferrite Nanoparticles as Nucleation Seeds.

In the present work, the crystallization of anatase TiO2 nanoparticles (NPs), using different ferrite nanoparticles with different chemical composition, dimensions and shape as nucleation seeds, was investigated. In particular, CoFe2O4, NiFe2O4 and Fe3O4 NPs with a volume ratio equal to 1:1000 with respect of TiO2 amount, were used in order to investigate the synthesis of nanocrystalline tetragonal anatase TiO2 by a hydrothermal synthesis. In addition, Lu2O3 nanoparticles were also used to detect the effect of a non-magnetic nanoparticle on the synthesis and nanocrystallization of titania. For each sample, a deep physical characterization was performed by XRD (with a Rietveld refinement of the structural data), FE-SEM, STEM, HRTEM, DSC analysis and BET surface area measurement. Furthermore, for some samples, the photocatalytic activity was investigated by degradation of methylene blue in aqueous medium, in the framework of a standard ISO 10678:2010 protocol. The hydrothermal synthesis was performed with a 3 hours' thermal treatment, at a pressure of approximatively 9 bar and a temperature significantly lower (Tmax═150 °C) than the usual temperature necessary to obtain crystalline anatase TiO2 (Tcryst═350 °C). The results give evidence that the mere presence of a nucleation seeds in the hydrothermal reactor, without any particular need for the composition and morphology, leads to crystalline anatase TiO2 nanoparticles with high photocatalytic performances.

High-Field Liquid-State Dynamic Nuclear Polarization in Microliter Samples.

Nuclear hyperpolarization in the liquid state by dynamic nuclear polarization (DNP) has been of great interest because of its potential use in NMR spectroscopy of small samples of biological and chemical compounds in aqueous media. Liquid state DNP generally requires microwave resonators in order to generate an alternating magnetic field strong enough to saturate electron spins in the solution. As a consequence, the sample size is limited to dimensions of the order of the wavelength, and this restricts the sample volume to less than 100 nL for DNP at 9 T (∼260 GHz). We show here a new approach that overcomes this sample size limitation. Large saturation of electron spins was obtained with a high-power (∼150 W) gyrotron without microwave resonators. Since high power microwaves can cause serious dielectric heating in polar solutions, we designed a planar probe which effectively alleviates dielectric heating. A thin liquid sample of 100 µm of thickness is placed on a block of high thermal conductivity aluminum nitride, with a gold coating that serves both as a ground plane and as a heat sink. A meander or a coil were used for NMR. We performed 1H DNP at 9.2 T (∼260 GHz) and at room temperature with 10 µL of water, a volume that is more than 100× larger than reported so far. The 1H NMR signal is enhanced by a factor of about -10 with 70 W of microwave power. We also demonstrated the liquid state of 31P DNP in fluorobenzene containing triphenylphosphine and obtained an enhancement of ∼200.

Antibacterial activity of standard and N-doped titanium dioxide-coated endotracheal tubes: an in vitro study. / Atividade antibacteriana de tubos endotraqueais revestidos com dióxido de titânio padrão e dopados com nitrogênio: um estudo in vitro.

OBJECTIVE:: The aim of this study was to assess the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa of two nanoparticle endotracheal tube coatings with visible light-induced photocatalysis. METHODS:: Two types of titanium dioxide nanoparticles were tested: standard anatase (TiO2) and N-doped TiO2 (N-TiO2). Nanoparticles were placed on the internal surface of a segment of commercial endotracheal tubes, which were loaded on a cellulose acetate filter; control endotracheal tubes were left without a nanoparticle coating. A bacterial inoculum of 150 colony forming units was placed in the endotracheal tubes and then exposed to a fluorescent light source (3700 lux, 300-700 nm wavelength) for 5, 10, 20, 40, 60 and 80 minutes. Colony forming units were counted after 24 hours of incubation at 37°C. Bacterial inactivation was calculated as the percentage reduction of bacterial growth compared to endotracheal tubes not exposed to light. RESULTS:: In the absence of light, no relevant antibacterial activity was shown against neither strain. For P. aeruginosa, both coatings had a higher bacterial inactivation than controls at any time point (p < 0.001), and no difference was observed between TiO2 and N-TiO2. For S. aureus, inactivation was higher than for controls starting at 5 minutes for N-TiO2 (p = 0.018) and 10 minutes for TiO2 (p = 0.014); inactivation with N-TiO2 was higher than that with TiO2 at 20 minutes (p < 0.001), 40 minutes (p < 0.001) and 60 minutes (p < 0.001). CONCLUSIONS:: Nanosized commercial and N-doped TiO2 inhibit bacterial growth under visible fluorescent light. N-TiO2 has higher antibacterial activity against S. aureus compared to TiO2.

Atividade antibacteriana de tubos endotraqueais revestidos com dióxido de titânio padrão e dopados com nitrogênio: um estudo in vitro / Antibacterial activity of standard and N-doped titanium dioxide-coated endotracheal tubes: an in vitro study

RESUMO Objetivo: Avaliar a atividade antibacteriana contra Staphylococcus aureus e Pseudomonas aeruginosa de dois revestimentos endotraqueais com nanopartículas e fotocatálise sob luz visível. Métodos: Testaram-se dois tipos de nanopartículas de titânio: anatase padrão (TiO2) e TiO2 nano-dopada (N-TiO2). As nanopartículas foram colocadas em superfície interna de segmentos de tubos endotraqueais comerciais, aplicadas sobre um filtro de acetato de celulose; os tubos endotraqueais controle foram deixados sem revestimento de nanopartículas. Em cada tubo endotraqueal foi inoculado um total de 150 unidades formadoras de colônia e, a seguir, estes foram expostos a uma fonte de luz fluorescente (3700 lux, comprimento de onda de 300 - 700nm) por 5, 10, 20, 40, 60 e 80 minutos. Contaram-se as Unidades Formadoras de Colônia após 24 horas de incubação a 37ºC. A inativação bacteriana foi calculada como a redução porcentual do crescimento bacteriano em comparação a tubos não expostos à luz. Resultados: Na ausência de luz, não se observou qualquer atividade antibacteriana relevante contra qualquer das cepas estudadas. Para P. aeruginosa, ambos os revestimentos tiveram inativação bacteriana mais elevada do que o controle em qualquer dos momentos de avaliação (p < 0,001), sendo que não se observaram diferenças entre o revestimento padrão e nano-dopado. Para S. aureus, a inativação foi maior que os controles, começando a partir de 5 minutos para nano-dopado (p = 0,018) e 10 minutos para o revestimento padrão (p = 0,014); a inativação com a forma nano-dopada foi maior do que com a forma padrão aos 20 minutos (p < 0,001), 40 minutos (p < 0,001) e 60 minutos (p < 0,001). Conclusões: O revestimento com nanopartículas de titânio comercial padrão e nano-dopado inibiu o crescimento bacteriano sob a luz fluorescente visível. o revestimento nano-dopado teve maior atividade antibacteriana contra S. aureus em comparação à atividade observada com o revestimento com anatase padrão.

ABSTRACT Objective: The aim of this study was to assess the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa of two nanoparticle endotracheal tube coatings with visible light-induced photocatalysis. Methods: Two types of titanium dioxide nanoparticles were tested: standard anatase (TiO2) and N-doped TiO2 (N-TiO2). Nanoparticles were placed on the internal surface of a segment of commercial endotracheal tubes, which were loaded on a cellulose acetate filter; control endotracheal tubes were left without a nanoparticle coating. A bacterial inoculum of 150 colony forming units was placed in the endotracheal tubes and then exposed to a fluorescent light source (3700 lux, 300-700 nm wavelength) for 5, 10, 20, 40, 60 and 80 minutes. Colony forming units were counted after 24 hours of incubation at 37°C. Bacterial inactivation was calculated as the percentage reduction of bacterial growth compared to endotracheal tubes not exposed to light. Results: In the absence of light, no relevant antibacterial activity was shown against neither strain. For P. aeruginosa, both coatings had a higher bacterial inactivation than controls at any time point (p < 0.001), and no difference was observed between TiO2 and N-TiO2. For S. aureus, inactivation was higher than for controls starting at 5 minutes for N-TiO2 (p = 0.018) and 10 minutes for TiO2 (p = 0.014); inactivation with N-TiO2 was higher than that with TiO2 at 20 minutes (p < 0.001), 40 minutes (p < 0.001) and 60 minutes (p < 0.001). Conclusions: Nanosized commercial and N-doped TiO2 inhibit bacterial growth under visible fluorescent light. N-TiO2 has higher antibacterial activity against S. aureus compared to TiO2.

500-fold enhancement of in situ (13)C liquid state NMR using gyrotron-driven temperature-jump DNP.

A 550-fold increase in the liquid state (13)C NMR signal of a 50µL sample was obtained by first hyperpolarizing the sample at 20K using a gyrotron (260GHz), then, switching its frequency in order to apply 100W for 1.5s so as to melt the sample, finally, turning off the gyrotron to acquire the (13)C NMR signal. The sample stays in its NMR resonator, so the sequence can be repeated with rapid cooling as the entire cryostat stays cold. DNP and thawing of the sample are performed only by the switchable and tunable gyrotron without external devices. Rapid transition from DNP to thawing in one second time scale was necessary especially in order to enhance liquid (1)H NMR signal.

Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260GHz.

An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260GHz at power levels less than 1W. The sweep rate of frequency modulation can reach 14kHz, and its amplitude is fixed at 50MHz. In water/glycerol glassy ice doped with 40mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15K, thus giving a DNP enhancement of about 80. By employing λ/4 and λ/8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power.

Enhancement of TiO2 NPs Activity by Fe3O4 Nano-Seeds for Removal of Organic Pollutants in Water.

The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, the crystallinity of TiO2 nanoparticles (NPs) seems to be affected by Fe3O4, acting as nano-seeds to improve the tetragonal TiO2 anatase structure with respect to the amorphous one. Photocatalytic activity data, i.e., the degradation of methylene blue and the Ofloxacin fluoroquinolone emerging pollutant, give evidence that the increased crystalline structure of the NPs, even if correlated to a reduced surface to mass ratio (with respect to commercial TiO2 NPs), enhances the performance of this type of catalyst. The achievement of a relatively well-defined crystal structure at low temperatures (Tmax = 150 °C), preventing the sintering of the TiO2 NPs and, thus, preserving the high density of active sites, seems to be the keystone to understand the obtained results.

Cryogenic single-chip electron spin resonance detector.

We report on the design and characterization of a single-chip electron spin resonance detector, operating at a frequency of about 20 GHz and in a temperature range extending at least from 300 K down to 4 K. The detector consists of an LC oscillator formed by a 200 µm diameter single turn aluminum planar coil, a metal-oxide-metal capacitor, and two metal-oxide-semiconductor field effect transistors used as negative resistance network. At 300 K, the oscillator has a frequency noise of 20 Hz/Hz(1/2) at 100 kHz offset from the 20 GHz carrier. At 4 K, the frequency noise is about 1 Hz/Hz(1/2) at 10 kHz offset. The spin sensitivity measured with a sample of DPPH is 10(8)spins/Hz(1/2) at 300 K and down to 10(6)spins/Hz(1/2) at 4 K.