Aging Compensation in a Class-A High-Frequency Amplifier with DC Temperature Measurements.

One of the threats to nanometric CMOS analog circuit reliability is circuit performance degradation due to transistor aging. To extend circuit operating life, the bias of the main devices within the circuit must be adjusted while the aging degradation process affects them by using a monitor circuit that tracks the evolution of the circuit performance. In this paper, we propose the use of DC temperature measurements in the proximity of the circuit to perform the monitoring of circuit performance degradation and as an observable variable to adjust the bias of the main devices to restore the degraded performance to the original values. To this end, we present experimental results obtained from nine samples of a standard CMOS integrated circuit containing a high-frequency class-A power amplifier and a differential temperature sensor. After accelerated aging, the gain of the amplifier is degraded up to 50%. We propose two different procedures to perform DC temperature measurements that allow tracking of the amplifier gain degradation due to aging and, by uniquely observing temperature readings, automatically set a new bias for the amplifier devices that restores the original amplifier gain. Whereas one of the procedures is able to restore the gain up to a certain limit, the second allows full gain restoration.

Plasmonic Titanium Nitride Tubes Decorated with Ru Nanoparticles as Photo-Thermal Catalyst for CO2 Methanation.

Photo-thermal catalysis has recently emerged as a viable strategy to produce solar fuels or chemicals using sunlight. In particular, nanostructures featuring localized surface plasmon resonance (LSPR) hold great promise as photo-thermal catalysts given their ability to convert light into heat. In this regard, traditional plasmonic materials include gold (Au) or silver (Ag), but in the last years, transition metal nitrides have been proposed as a cost-efficient alternative. Herein, we demonstrate that titanium nitride (TiN) tubes derived from the nitridation of TiO2 precursor display excellent light absorption properties thanks to their intense LSPR band in the visible-IR regions. Upon deposition of Ru nanoparticles (NPs), Ru-TiN tubes exhibit high activity towards the photo-thermal CO2 reduction reaction, achieving remarkable methane (CH4) production rates up to 1200 mmol g-1 h-1. Mechanistic studies suggest that the reaction pathway is dominated by thermal effects thanks to the effective light-to-heat conversion of Ru-TiN tubes. This work will serve as a basis for future research on new plasmonic structures for photo-thermal applications in catalysis.

Fundamentals and applications of photo-thermal catalysis.

Correction for 'Fundamentals and applications of photo-thermal catalysis' by Diego Mateo et al., Chem. Soc. Rev., 2021, 50, 2173-2210, DOI: 10.1039/D0CS00357C.

Tunable Selectivity in CO2 Photo-Thermal Reduction by Perovskite-Supported Pd Nanoparticles.

Photo-thermal catalysis has recently emerged as a promising alternative to overcome the limitations of traditional photocatalysis. Despite its potential, most of the photo-thermal systems still lack adequate selectivity patterns and appropriate analysis of the underlying reaction pathways, thus hampering a wide implementation. Herein, a novel photocatalyst based on Pd nanoparticles (NPs) supported on barium titanate (BTO) was prepared for the selective photo-thermal reduction of CO2 and displayed catalytic rates of up to 8.2 molCO gPd -1 h-1 . The photocatalyst allowed for a tailored selectivity towards CO or CH4 as a function of the metal loading or the light intensity. Mechanistic studies indicated that both thermal and non-thermal contributions of light played a role in the overall reaction pathway, each of them being dominant upon changing reaction conditions.

An Efficient Metal-Organic Framework-Derived Nickel Catalyst for the Light Driven Methanation of CO2.

We report the synthesis of a highly active and stable metal-organic framework derived Ni-based catalyst for the photothermal reduction of CO2 to CH4 . Through the controlled pyrolysis of MOF-74 (Ni), the nature of the carbonaceous species and therefore photothermal performance can be tuned. CH4 production rates of 488 mmol g-1 h-1 under UV-visible-IR irradiation are achieved when the catalyst is prepared under optimized conditions. No particle aggregation or significant loss of activity were observed after ten consecutive reaction cycles or more than 12 hours under continuous flow configuration. Finally, as a proof-of-concept, we performed an outdoor experiment under ambient solar irradiation, demonstrating the potential of our catalyst to reduce CO2 to CH4 using only solar energy.

BPF-Based Thermal Sensor Circuit for On-Chip Testing of RF Circuits.

A new sensor topology meant to extract figures of merit of radio-frequency analog integrated circuits (RF-ICs) was experimentally validated. Implemented in a standard 0.35 µm complementary metal-oxide-semiconductor (CMOS) technology, it comprised two blocks: a single metal-oxide-semiconductor (MOS) transistor acting as temperature transducer, which was placed near the circuit to monitor, and an active band-pass filter amplifier. For validation purposes, the temperature sensor was integrated with a tuned radio-frequency power amplifier (420 MHz) and MOS transistors acting as controllable dissipating devices. First, using the MOS dissipating devices, the performance and limitations of the different blocks that constitute the temperature sensor were characterized. Second, by using the heterodyne technique (applying two nearby tones) to the power amplifier (PA) and connecting the sensor output voltage to a low-cost AC voltmeter, the PA's output power and its central frequency were monitored. As a result, this topology resulted in a low-cost approach, with high linearity and sensitivity, for RF-IC testing and variability monitoring.

Fundamentals and applications of photo-thermal catalysis.

Photo-thermal catalysis has recently emerged as an alternative route to drive chemical reactions using light as an energy source. Through the synergistic combination of photo- and thermo-chemical contributions of sunlight, photo-thermal catalysis has the potential to enhance reaction rates and to change selectivity patterns, even under moderate operation conditions. This review provides the fundamentals of localized surface plasmon resonance (LSPR) that explain the photo-thermal effect in plasmonic structures, describes the different mechanistic pathways underlying photo-thermal catalysis, suggests methodologies to disentangle the reaction mechanisms and proposes material design strategies to improve photo-thermal performance. Ultimately, the goal is to pave the way for the wide implementation of this promising technology in the production of synthetic fuels and chemicals.

Differential Temperature Sensors: Review of Applications in the Test and Characterization of Circuits, Usage and Design Methodology.

Differential temperature sensors can be placed in integrated circuits to extract a signature of the power dissipated by the adjacent circuit blocks built in the same silicon die. This review paper first discusses the singularity that differential temperature sensors provide with respect to other sensor topologies, with circuit monitoring being their main application. The paper focuses on the monitoring of radio-frequency analog circuits. The strategies to extract the power signature of the monitored circuit are reviewed, and a list of application examples in the domain of test and characterization is provided. As a practical example, we elaborate the design methodology to conceive, step by step, a differential temperature sensor to monitor the aging degradation in a class-A linear power amplifier working in the 2.4 GHz Industrial Scientific Medical-ISM-band. It is discussed how, for this particular application, a sensor with a temperature resolution of 0.02 K and a high dynamic range is required. A circuit solution for this objective is proposed, as well as recommendations for the dimensions and location of the devices that form the temperature sensor. The paper concludes with a description of a simple procedure to monitor time variability.

Long-Term Photostability in Terephthalate Metal-Organic Frameworks.

Prolonged (weeks) UV/Vis irradiation under Ar of UiO-66(Zr), UiO66 Zr-NO2 , MIL101 Fe, MIL125 Ti-NH2 , MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD-containing MOFs, zeolitic imidazolate ZIF-8 does not evolve CO2 or any other gas upon irradiation.

De novo synthesis of mesoporous photoactive titanium(iv)-organic frameworks with MIL-100 topology.

Most developments in the chemistry and applications of metal-organic frameworks (MOFs) have been made possible thanks to the value of reticular chemistry in guiding the unlimited combination of organic connectors and secondary building units (SBUs) into targeted architectures. However, the development of new titanium-frameworks still remains limited by the difficulties in controlling the formation of persistent Ti-SBUs with predetermined directionality amenable to the isoreticular approach. Here we report the synthesis of a mesoporous Ti-MOF displaying a MIL-100 topology. MIL-100(Ti) combines excellent chemical stability and mesoporosity, intrinsic to this archetypical family of porous materials, with photoactive Ti3(µ3-O) metal-oxo clusters. By using high-throughput synthetic methodologies, we have confirmed that the formation of this SBU is thermodynamically favored as it is not strictly dependent on the metal precursor of choice and can be regarded as an adequate building block to control the design of new Ti-MOF architectures. We are confident that the addition of a mesoporous solid to the small number of crystalline, porous titanium-frameworks available will be a valuable asset to accelerate the development of new porous photocatalysts without the pore size limitations currently imposed by the microporous materials available.

Graphene-Based Materials as Efficient Photocatalysts for Water Splitting.

Photocatalysis has been proposed as one of the most promising approaches for solar fuel production. Among the photocatalysts studied for water splitting, graphene and related materials have recently emerged as attractive candidates due to their striking properties and sustainable production when obtained from biomass wastes. In most of the cases reported so far, graphene has been typically used as additive to enhance its photocatalytic activity of semiconductor materials as consequence of the improved charge separation and visible light harvesting. However, graphene-based materials have demonstrated also intrinsic photocatalytic activity towards solar fuels production, and more specifically for water splitting. The photocatalytic activity of graphene derives from defects generated during synthesis or their introduction through post-synthetic treatments. In this short review, we aim to summarize the most representative examples of graphene based photocatalysts and the different approaches carried out in order to improve the photocatalytic activity towards water splitting. It will be presented that the introduction of defects in the graphenic lattice as well as the incorporation of small amounts of metal or metal oxide nanoparticles on the graphene surface improve the photocatalytic activity of graphene. What is more, a simple one-step preparation method has demonstrated to provide crystal orientation to the nanoparticles strongly grafted on graphene resulting in remarkable photocatalytic properties. These two features, crystal orientation and strong grafting, have been identified as a general methodology to further enhance the photocatalytic activity in graphenebased materials for water splitting. Finally, future prospects in this filed will be also commented.

Synergism of Au and Ru Nanoparticles in Low-Temperature Photoassisted CO2 Methanation.

Au and Ru nanoparticles (NPs) have been deposited on Siralox® substrate by impregnation and chemical reduction, respectively (Au-Ru-S). The as-prepared material is very active in the selective CO2 methanation to CH4 at temperatures below 250 °C. In addition, Au-Ru-S shows enhanced CH4 production upon irradiation with UV/Vis light starting at temperatures higher than 200 °C, although the contribution of the photoassisted pathway of CH4 production decreases as the temperature increases. Thus, a maximum CH4 production of 204 mmol gRu -1 at 250 °C upon 100 mW cm-2 irradiation was achieved. Control experiments, in which Ru-S and Au-S materials were used, revealed that Ru NPs are the CO2 methanation active sites, while Au NPs contribute by harvesting light, mainly visible as a consequence of the strong Au plasmon band centered at 529 nm. The visible light absorbed by the plasmonic band of Au NPs could make them act ass local heaters of the neighboring Ru NPs, increasing their temperature and enhancing CH4 production.

The mechanism of photocatalytic CO2 reduction by graphene-supported Cu2O probed by sacrificial electron donors.

Cu2O nanoparticles of 5 nm average size have been adsorbed (1.74 wt% loading) on defective graphene (Cu2O/G) previously obtained by the pyrolysis of alginic acid sodium salt. The Cu2O crystal phase was determined by XRD. XPS shows that the external layers of the Cu2O nanoparticles are constituted mainly of Cu+ although a certain percentage of CuII+ was also present. Cu2O/G is a photocatalyst for the CO2 reduction to methane in the presence of sacrificial agents, and the rate of CH4 production depends on the oxidation potential of the electron donor. This relationship supports a mechanism involving photoinduced charge separation with the generation of electrons and holes. The highest CH4 formation rate upon UV-Vis irradiation of Cu2O/G with a 300 W Xe lamp was achieved for dimethylaniline reaching 326 µmol CH4 per g per h. The spectral response of the Cu2O photocatalyst shows, however, that the response of the photocatalyst is mainly due to UV irradiation, indicating that light absorption at the low Cu2O loading on the Cu2O/G photocatalyst occurs mainly on the graphene component.

Gas-Phase Photochemical Overall H2 S Splitting by UV Light Irradiation.

Splitting of hydrogen sulfide is achieved to produce value-added chemicals. Upon irradiation at 254 nm in the gas phase and in the absence of catalysts or photocatalysts at near room temperature, H2 S splits into stoichiometric amounts of H2 and S with a quantum efficiency close to 50 %. No influence of the presence of CH4 and CO2 (typical components in natural gas and biogas in which H2 S is an unwanted component) on the efficiency of overall H2 S splitting was observed. A mechanism for the H2 and S formation is proposed.

111 oriented gold nanoplatelets on multilayer graphene as visible light photocatalyst for overall water splitting.

Development of renewable fuels from solar light appears as one of the main current challenges in energy science. A plethora of photocatalysts have been investigated to obtain hydrogen and oxygen from water and solar light in the last decades. However, the photon-to-hydrogen molecule conversion is still far from allowing real implementation of solar fuels. Here we show that 111 facet-oriented gold nanoplatelets on multilayer graphene films deposited on quartz is a highly active photocatalyst for simulated sunlight overall water splitting into hydrogen and oxygen in the absence of sacrificial electron donors, achieving hydrogen production rate of 1.2 molH2 per gcomposite per h. This photocatalytic activity arises from the gold preferential orientation and the strong gold-graphene interaction occurring in the composite system.

Interactions of manufactured silver nanoparticles of different sizes with normal human dermal fibroblasts.

Silver compounds have been used for their medicinal properties for centuries. At present, silver nanoparticles (AgNPs) are reemerging as a viable topical treatment option for infections encountered in burns, open wounds and chronic ulcers. This study evaluated the in vitro mechanisms of two different sizes of AgNPs (4·7 and 42 nm) toxicity in normal human dermal fibroblasts. The toxicity was evaluated by observing cell viability and oxidative stress parameters. In all toxicity endpoints studied (MTT and lactate dehydrogenase assays), AgNPs of 4·7 nm were much more toxic than the large AgNPs (42 nm). The cytotoxicity of both AgNPs was greatly decreased by pre-treatment with the antioxidant N-acetyl-L-cysteine. The oxidative stress parameters showed significant increase in reactive oxygen species levels, depletion of glutathione level and slight, but not statistically significant inactivation of superoxide dismutase, suggesting generation of oxidative stress. Thus, AgNPs should be used with caution for the topical treatment of burns and wounds, medical devices etc, because their toxicity depends on the size, the smaller NPs being much more cytotoxic than the large.

Effects of silver and gold nanoparticles of different sizes in human pulmonary fibroblasts.

Silver and gold nanoparticles (Ag-AuNPs) are currently some of the most manufactured nanomaterials. Accordingly, the hazards associated with human exposure to Ag-AuNPs should be investigated to facilitate the risk assessment process. In particular, because pulmonary exposure to Ag-AuNPs occurs during handling of these nanoparticles, it is necessary to evaluate the toxic response in pulmonary cells. The aim of this study was to evaluate the in vitro mechanisms of toxicity of different sizes of silver (4.7 and 42 nm) and gold nanoparticles (30, 50 and 90 nm) in human pulmonary fibroblasts (HPF). The toxicity was evaluated by observing cell viability and oxidative stress parameters. Data showed that AgNPs-induced cytotoxicity was size-dependent, whereas the AuNPs of the three sizes showed similar cytotoxicity. Silver nanoparticles of 4.7 nm were much more toxic than the large silver nanoparticles and the AuNPs. However, the pre-treatment with the antioxidant, N-acetyl-L-cysteine, protected HPF cells against treatment with Ag-AuNPs. The oxidative stress parameters revealed significant increase in reactive oxygen species levels, depletion of glutathione level and slight, but not statistically significant inactivation of superoxide dismutase, suggesting generation of oxidative stress. Hence, care has to be taken while processing and formulating the Ag-AuNPs till their final finished product.

Cytotoxicity and ROS production of manufactured silver nanoparticles of different sizes in hepatoma and leukemia cells.

Silver nanoparticles (AgNPs), which have well-known antimicrobial properties, are extensively used in various medical and general applications. In spite of the widespread use of AgNPs, relatively few studies have been undertaken to determine the cytotoxic effects of AgNPs. The aim of this study was investigate how AgNPs of different sizes (4.7 and 42 nm) interact with two different tumoral human cell lines (hepatoma [HepG2] and leukemia [HL-60]). In addition, glutathione depletion, inhibition of superoxide dismutase (SOD) and reactive oxygen species (ROS) generation were used to evaluate feasible mechanisms by which AgNPs exerted its toxicity. AgNPs of 4.7 nm and 42 nm exhibited a dramatic difference in cytotoxicity. Small AgNPs were much more cytotoxic than large AgNPs. A difference in the cellular response to AgNPs was found. HepG2 cells showed a higher sensitivity to the AgNPs than HL-60. However, the cytotoxicity induced by AgNPs was efficiently prevented by NAC treatment, which suggests that oxidative stress is primarily responsible for the cytotoxicity of AgNPs. Furthermore, cellular antioxidant status was disturbed: AgNPs exposure caused ROS production, glutathione depletion and slight, but not statistically significant inactivation of SOD.

Oxidative stress contributes to gold nanoparticle-induced cytotoxicity in human tumor cells.

Due to their exceptional properties, gold nanoparticles (AuNPs) have shown promising medical and technological applications in the treatment of cancer and the development of antimicrobial packaging and time-temperature indicators in the food sector. However, little is known about their cytotoxicity when they come into contact with biological systems. The aim of this work was to compare the effects of three commercially available AuNPs of different sizes (30, 50 and 90 nm) on human leukemia (HL-60) and hepatoma (HepG2) cell lines. AuNP-induced cytotoxicity was dose and time-dependent, with IC50 values higher than 15 µg/mL. Nanoparticle (NP) size and cell line slightly influenced on the cytotoxicity of AuNPs, although HL-60 cells proved to be more sensitive to the cytotoxic response than HepG2. N-Acetyl-L-cysteine (NAC) protected HL-60 and HepG2 cells only against treatment with 30 nm AuNPs. In both cell types, glutathione (GSH) content was drastically depleted after 72 h of incubation with the three AuNPs (less than 30% in all cases), while the reduction of superoxide dismutase activity (SOD) activity depended on cell line. HepG2, but not HL-60 cells, exhibited a decrease of SOD activity (∼ 45% of activity). The three AuNPs also caused a two-fold elevation of reactive oxygen species (ROS) production in both cell lines. Thus, protective effect of NAC, depletion of GSH and increase of ROS appear to be determined by NP size and indicate that oxidative stress contributes to cytotoxicity of AuNPs.

Nanopartículas de oro: aplicaciones y citotoxicidad in vitro / Gold nanoparticles: Applications and in vitro cytotoxicity

En los últimos años, la evolución en el desarrollo de productos elaborados a partir de nanotecnología ha experimentado un espectacular crecimiento. En particular, las nanopartículas de oro han despertado gran interés en los sectores biomédico y alimentario, donde se ha descrito su utilización en el tratamiento frente al cáncer o como parte integrante de envases resistentes a la abrasión, con propiedades antimicrobianas. Por tanto, se cree que la exposición humana a las nanopartículas de oro aumentará considerablemente en los próximos años, pudiendo tener esto repercusiones sobre la salud. En este marco, el estudio de la toxicología de las nanopartículas ha revelado que su toxicidad depende de multitud de factores. Además, en la bibliografía hay cierta controversia en torno a los posibles efectos citotóxicos inducidos por las nanopartículas de oro. Diversos estudios de exposición in vitro han destacado su inocuidad en algunas líneas celulares, mientras que otros trabajos demostraron respuesta citotóxica. La siguiente revisión tiene por objeto describir las propiedades más relevantes de las nanopartículas de oro considerando sus potenciales aplicaciones en medicina y en la industria de los alimentos, así como examinar su posible toxicidad, con especial énfasis en los estudios de citotoxicidad in vitro disponibles hasta el momento.

In the recent years, the development of nanotechnology-based products has experienced a spectacular growth. Especially, gold nanoparticles have awoken a great interest in the biomedical and food sector, where their applications in cancer treatment as well as their incorporation in abrasion resistant and antimicrobial packaging have been described. Therefore, it is believed that human exposure to gold nanoparticles will increase considerably in the next few years, which may arise possible human health hazards. Hence, toxicology studies on nanoparticles revealed that their toxicity depends on various factors. Furthermore, there is some controversy regarding to gold nanoparticle-induced cytotoxicity. Several in vitro studies have reported that gold nanoparticles are innocuous, while some investigations have demonstrated a cytotoxic response after the exposure to these. The aim of this review is to describe the most relevant properties of gold nanoparticles according to their possible applications in medicine and in food industry, as well as to provide information about their possible toxic effects, taking into account the cytotoxic in vitro studies published at present.