On-off Cycles Research Articles

Process of ammonia removal from anaerobic digestion and associated ammonium sulphate production: Pilot plant demonstration

A process for the continuous extraction of ammonia from anaerobic digesters is proposed. In this process, a portion of the sludge treated in the digesters is continuously withdrawn and transferred to a thin film evaporator (TFE) unit, where the ammonia is stripped through a biogas stream. The ammonia-rich biogas is treated with a sulfuric acid/water solution in a reactive absorption unit, with production of ammonium sulphate. The chemistry of a CH4/CO2/NH3 gas phase in thermodynamic equilibrium with a liquid sulfuric acid/water solution is investigated theoretically, with focus on the simultaneous absorption of CO2 and NH3 into the liquid phase. Pilot plant experimental data confirm the theoretical results. Further pilot plant experimental results obtained during on-off cycles of the stripping equipment demonstrate that, when the TFE unit is off, ammonia concentration in the digestate rises quickly, while, when the stripping equipment is turned on again, ammonia concentration drops down. On average, during the 180 days of pilot plant experimentation, 4.1 g N–NH4 per kg of sludge fed to the digester, i.e. 19.3 g N–NH4 per kg of total solids (TS) fed to the digester, are stripped from digestate and recovered as ammonium sulphate, demonstrating the feasibility of the proposed concept.

Life cycle cost analysis of different residential heat pump systems

Nowadays, the application of air-source heat pumps for heating and cooling in residential buildings has been increased significantly. The main occasion for this is the accessibility of a heat source for these devices - the external air. Nevertheless, the increase of the energy efficiency of the air source heat pump systems is a difficult design problem because their capacity and performance are a function of the dynamically changing parameters of the outdoor air. Because of that, the main aim of this study is to develop an approach for choosing a structural scheme of an air-to-water heat pump system under specific climatic conditions. The considered systems are monovalent, bivalent-parallel and bivalent-alternative heat pump systems. In the current paper is conducted a dynamic energy modeling of heating and cooling demand of a typical residential building situated in Varna, Bulgaria and applying the bin temperature data. It is assessed the effect of the heat pump capacity over the annual and seasonal energy performance of the heat pump systems. It is established the effect of the bivalent temperature, cut-off temperature and on-off cycles duration on rates of the criteria for techno-economic assessment. The seasonal coefficient of performance (SCOP), seasonal energy efficiency rate (SEER) and life cycle costs (LCC) of the analyzed heat pump systems are adopted as assessment parameters.

In-Situ Growth and Immobilization of CdS Nanoparticles onto Functionalized MoS2 : Preparation, Characterization and Fabrication of Photoelectrochemical Cells.

A facile strategy for the controllable growth of CdS nanoparticles at the periphery of MoS2 en route the preparation of electron donor-acceptor nanoensembles is developed. Precisely, the carboxylic group of α-lipoic acid, as addend of the modified MoS2 obtained upon 1,2-dithiolane functionalization, was employed as anchor site for the in situ preparation and immobilization of the CdS nanoparticles in an one-pot two-step process. The newly prepared MoS2 /CdS hybrid material was characterized by complementary spectroscopic, thermal and microscopy imaging means. Absorption spectroscopy was employed to register the formation of MoS2 /CdS, by observing a broad shoulder centered at 420 nm due to CdS nanoparticles, while the excitonic bands of MoS2 were also evident. Moreover, based on the efficient quenching of the characteristic fluorescence emission of CdS at 725 nm by the presence of MoS2 , strong electronic interactions at the excited state between the two species within the ensemble were identified. Photoelectrochemical assays of MoS2 /CdS thin-film electrodes revealed a prompt, steady and reproducible anodic photoresponse during repeated on-off cycles of illumination. A significant zero-current photopotential of -540 mV and an anodic photocurrent of 1 μA were observed, underlining improved charge-separation and electron transport from CdS to MoS2 . The superior performance of the charge-transfer processes in MoS2 /CdS is of direct interest for the fabrication of photoelectrochemical and optoelectronic devices.

On-Demand Sonochemical Synthesis of Ultrasmall and Magic-Size CdSe Quantum Dots in Single-Phase and Emulsion Systems.

The sonochemical synthesis of CdSe quantum dots (QDs) in a single-liquid bulk phase and in an emulsion-based system is presented. Reactions utilized cadmium oleate and trioctylphosphine selenide precursors and were monitored as a function of sonication time under controlled temperature conditions to isolate the effects of cavitation from those of bulk temperature changes. QD synthesis was found to be slow in the single-phase liquid system (i.e., 1-octadecene) but greatly accelerated in the dispersed system (i.e., emulsions of 1-octadecene in ethylene glycol). It is hypothesized that the emulsion system increases the cavitation efficiency while also delivering acoustic energy in closer proximity to the precursor molecules. The capacity of CdSe production in the emulsion system was found to be 3.8 g/(L h), which is comparable to the typical hot-injection synthesis of CdSe QDs and can likely be further optimized. While the single-phase solvent system was found to produce ultrasmall QDs that exhibit broadband white-light emission, the emulsion system was found to produce well-defined magic-size clusters (MSCs) with photoluminescence quantum yield as high as 34%. Differences in synthesis rate and product properties from the emulsion and single-phase systems were probed by X-ray diffraction, electron microscopy, UV-visible (vis) and photoluminescence spectroscopy, and small-angle X-ray scattering (SAXS). Finally, precise temporal control of the QD synthesis was demonstrated via on-off cycling of the ultrasound waves.

Impact of field ramp rate on magnetic field assisted thermal transport in ferrofluids

The impact of magnetic field ramp rate and the resulting aggregation kinetics on thermal transport in three different oil based ferrofluids of similar properties but with different particle size distributions is reported here. The volume fraction of the surfactant capped magnetite nanoparticles, in all three cases were kept constant at 0.037(20 wt%). For 17 G/s ramp thermal conductivity enhancement of 180% at 200 G improved to 230% with 33 G/s ramp in the ferrofluid system with the least fraction of larger particles. Our results show that faster magnetic field ramps have a profound influence on thermal conductivity enhancement. The phase contrast optical microscopy images show that the slower ramps resulted in thicker aggregates leading to a substantial decrease in their number density. On the other hand, faster ramps resulted in simultaneous formation of large number density of finer aggregates which proved to be extremely beneficial for thermal transport. In a ferrofluid with moderately high number of larger particles, faster ramps were found to be very effective in improving thermal transport. On sudden exposure to magnetic field, particularly for higher strengths, substantial improvement in thermal conductivity was observed initially, which decreased with time due to coarsening of aggregates and reduced number density of chains, but leveled off to a lower time independent value. Our findings provide a way to improve field induced thermal transport of a ferrofluid without altering their physical properties. Alternate magnetic field on-off cycles and faster field ramps were found to be particularly helpful in improving thermal transport of a ferrofluid possessing modest amount of larger particles, which will enable development of superior smart cooling devices.

Novel Green Micro-Synthesis of Graphene-Titanium Dioxide Nano- Composites with Photo-Electrochemical Properties

Background: Graphene-Titanium dioxide nano-composite forms a very promising material in the field of photo-electrochemical research. Methods: In this study, a novel environment-friendly synthesis method was developed to produce well-distributed anatase nano-titanium dioxide spherical particles on the surface of graphene sheets. This novel method has great advantages over previously developed methods of producing graphenetitanium dioxide nanocomposites (GTNCs). High calcination temperature 650°C was used in the preparation of nano titanium dioxide, and chemical exfoliation for graphene synthesis and GTNC was performed by our novel method of depositing titanium dioxide nanoparticles on graphene sheets using a Y-shaped micro-reactor under a controlled pumping rate with minimal use of chemicals. Results: The physiochemical and crystallographic properties of the GTNC were confirmed by TEM, XRD, FTIR and EDX measurements, confirming process repeatability. Spherical nano-titanium dioxide was produced in the anatase phase with very high crystallinity and small particle diameters ranging from 9 nm to 25 nm, also the as prepared graphene (RGO) exhibited minimal flake folding and a high carbon content of 81.28% with a low oxygen-to-carbon atomic ratio of 0.172 and GTNCs produced by our novel method had a superior loading content, a homogeneous distribution and a 96.6% higher content of titanium dioxide particles on the graphene sheets compared with GTNCs prepared with the one-pot method. Conclusion: For its photoelectrochemical properties, chronoamperometry showed that GTNC sample (2) had a higher peak current of 60 μA compared with that of GTNC sample (1), which indicates that the separation and transfer of electron-hole pairs are better in the case of GTNC sample (2) and according to the LSV results, the generation of photocurrent in the samples can be observed through multiple on-off cycles, which indicates that the electrodes are stable and that the photocurrent is quite reversible.

Simulation on the Interfacial Singular Stress-strain Induced Cracking of Microelectronic Chip Under pPower On-off Cycles

Thermal fatigue failure of a microelectronic chip usually initiates from the interface between solder joint and substrate for the mismatch in coefficient of thermal expansion (CTE). Because of the viscoelastic creep properties of the solder, the interfacial stress-strain are, strongly, temperature and time dependent. Based on the established constitutive models of solder materials, the three-dimensional FEM analysis of the microelectronic chip undergoing power on-off thermal cycles is carried out. The time dependent stress-strain singular fields at the solder/substance interface are obtained, and the singular field parameters are quantitatively evaluated. Furthermore, the crack nucleation behavior of thermal fatigue failure are tested to verify the conclusion that singular stress-strain promote thermal fatigue failure from the solder/substance interface.

Multi-pulse characterization of trapping/detrapping mechanisms in AlGaN/GaN high electromobility transistors

GaN high-electro mobility transistors (HEMTs) are among the most promising candidates for use in high-power, high-frequency, and high-temperature electronics owing to their high electrical breakdown threshold and their high saturation electron velocity. The applications of these AlGaN/GaN HEMTs in power converters are limited by the surface trapping effects of drain-current collapse. Charge-trapping mechanisms affect the dynamic performance of all GaN HEMTs used in power switching applications. This study analyzes the dynamic resistance of GaN HEMTs and finds that the effects of dynamic resistance can be suppressed by controlling switching conditions and on-off cycles.

Water-stable Adenine-based MOFs with Polar Pores for Selective CO2 Capture.

Here, we report two novel water-stable amine-functionalized MOFs, namely IISERP-MOF26 ([NH2 (CH3 )2 ][Cu2 O(Ad)(BDC)]⋅(H2 O)2 (DMA), 1) and IISERP-MOF27 ([NH2 (CH3 )2 ]1/2 [Zn4 O(Ad)3 (BDC)2 ]⋅(H2 O)2 (DMF)1/2 , 2), which show selective CO2 capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N-rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA+ ) cations in the pore rendering an electrostatic environment within the channels. The activated Cu- and Zn-MOFs physisorb about 2.7 and 2.2 mmol g-1 of CO2 , respectively, with high CO2 /N2 and moderate CO2 /CH4 selectivity. The calculated heat of adsorption (HOA=21-23 kJ mol-1 ) for the CO2 in both MOFs suggest optimal physical interactions which corroborate well with their facile on-off cycling of CO2 . Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO2 uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO2 capture applications. However, the MOF's low heat of adsorption despite having a highly CO2 -loving groups lined walls is quite intriguing.

Bipolar Cu/HfO2/p++ Si Memristors by Sol-Gel Spin Coating Method and Their Application to Environmental Sensing

In this paper, the memristive switching behavior of Cu/ HfO2/p++ Si devices fabricated by an organic-polymer-assisted sol-gel spin-coating method, coupled with post-annealing and shadow-mask metal sputtering steps, is examined. HfO2 layers of about 190 nm and 80 nm, are established using cost-effective spin-coating method, at deposition speeds of 2000 and 4000 rotations per minute (RPM), respectively. For two types of devices, the memristive characteristics (Von, Ion, and Vreset) and device-to-device electrical repeatability are primarily discussed in correlation with the oxide layer uniformity and thickness. The devices presented in this work exhibit an electroforming free and bipolar memory-resistive switching behavior that is typical of an Electrochemical Metallization (ECM) I-V fingerprint. The sample devices deposited at 4000 RPM generally show less variation in electrical performance parameters compared to those prepared at halved spin-coating speed. Typically, the samples prepared at 4000 RPM (n = 8) display a mean switching voltage Von of 3.0 V (±0.3) and mean reset voltage Vreset of −1.1 V (±0.5) over 50 consecutive sweep cycles. These devices exhibit a large Roff/Ron window (up to 104), and sufficient electrical endurance and retention properties to be further examined for radiation sensing. As they exhibit less statistical uncertainty compared to the samples fabricated at 2000 RPM, the devices prepared at 4000 RPM are tested for the detection of soft gamma rays (emitted from low-activity Cs-137 and Am-241 radioactive sources), by assessing the variation in the on-state resistance value upon exposure. The analysis of the probability distributions of the logarithmic Ron values measured over repeated ON-OFF cycles, before, during and after exposing the devices to radiation, demonstrate a statistical difference. These results pave the way for the fabrication and development of cost-effective soft-gamma ray detectors.

Energy, Exergy and Anergy Analysis of Vertical Split Air Conditioner Under experimental ON-OFF Cycling

A time series analysis can help to observe the behavior of the system and specify the system faults. In addition, it also helps to explain the various energy flows in the system and further aid in reducing the thermodynamic losses. The intelligent supervisory LabVIEW software can monitor the incoming data from the system by using Arduino microcontroller and calculates the important parameters. Energy, exergy, and anergy analysis present in this paper to investigate the system performance as well as its components. To accomplish this, a 4-ton vertical split air conditioner based on vapor compression refrigeration cycle charged with refrigerant R-22 was modified for experimental analysis. The results showed that during 5400 secs of experimental study, the system shut down once by the software for 5 min. The volumetric and isentropic efficiencies of the compressor were 79.85 % and 64.48 % respectively. The maximum entropy generation was due to the compressor of 3.4 W/K while the maximum anergy was due to the condenser of 1.39 kW. The exergy efficiencies of the compressor, condenser, and the evaporator were 73.57, 40.18, and 47.45 % respectively. The system and Carnot COP were 2.53 and 4.9 respectively. The exergy efficiency of the air conditioning system was 48.7 %.

On-off cycling losses of reversible air-to-water heat pump systems as a function of the unit power modulation capacity

In this paper, the impact of on-off cycling losses on the seasonal energy performances of three reversible air-to-water heat pumps having equivalent thermal performance at full load but different power modulation capacity is discussed by means of a series of dynamic simulation models. The analysis of the heat pump performance at partial load, the development and comparison of different control algorithms for heat pumps and, finally, the modeling and evaluation of the degradation effect due to the heat pump on-off cycles at partial load conditions are numerically investigated by means of a series of innovative TRNSYS models not available in the software standard library. The models are able to take into account the variation of the heat pump performance at partial load conditions for multi-stage, inverter-driven and single-stage devices. The findings of this paper point out that the energy losses introduced during the start-up transient of the heat pump has a significant impact on the overall energy performance of the system only for single-stage units, which perform on-off cycles during the whole season, with a decrease of the seasonal performance factor (SPF) up to 12%. On the other hand, modulating heat pumps (i.e. multi-stage and inverter-driven units) avoid carrying out on-off cycles and, of course, cycling losses for a significant part of the season according to their enhanced modulation capacity. It is shown how the accurate dynamic simulation of heat pump-based systems is a useful tool for HVAC designers in order to optimize their control system parameters, with the aim to reduce the compressor maximum hourly number of cycles.

High efficient photo detector by using ZnO nanowire arrays on highly aligned electrospun PVDF-TrFE nanofiber film

Zinc oxide(ZnO) is a versatile semiconductor material and its use is expanding into photoelectric applications. Anisotropic growth characteristics of ZnO are advantageous for growing a nanowire structure. ZnO nanowire based sensors exhibit enhanced performance in terms of photodetection due to their large specific surface area. ZnO nanowires on a highly aligned electrospun poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) nanofiber-based film are fabricated high performance ultraviolet (UV) detector. The movement of photo-induced electrons from ZnO nanowires is more effective in aligned electrospun film substrate (Rsq,off/Rsq,on = 551.0) than random electrospun film substrate (Rsq,off/Rsq,on = 47.8) under continuous UV irradiation. The current difference is 3.98 times higher on ZnO nanowires on aligned electrospun film than it is on random electrospun film in UV light on-off cycles. As a result, we improve the performance of photo sensitivity of electrospun nanofiber-based ZnO nanowires through controlling the directionality and fabrication time of the electrospun film without additional processes.

A wireless smart patch for the controlled repetitive transdermal administration of therapeutic agents

A thermoresistive transdermal drug delivery patch based on a n-alkane wax phase change film is described. A composite structure comprising a screen printed silver chloride heater sandwiched with a wax film loaded with diclofenac was developed and the release characteristics upon heating were investigated. The drug is shown to be immobile within the solid film (off state) but is readily delivered upon heating beyond the transition temperature (37 °C). Drug delivery is maintained while the heater is active and terminates upon cooling. The system has been shown to be capable of repetitive on-off cycling with control effected through a Bluetooth connection to a smart phone app with dynamic feedback control/thermoregulation of the patch.

A Rab4‐Regulated Endosomal Compartment Prolongs EGFR Activation in Breast Cancer Cells

Early sorting endosomes are responsible for the proper trafficking of membrane-bound receptors that can drive cancer progression. However, the morphology, cargo sorting and signaling of early endosomes remains poorly understood in breast cancer. We have identified a novel population of enlarged early endosomal vesicles in breast cancer cells and human tumor xenografts (MDAMB231 and T47D) but not in non-cancerous epithelial cells (MCF10A) using confocal and super-resolution 3D dSTORM microscopy. A detailed quantitative analysis of the whole-cell endosomal morphology, cargo sorting, maturation, and regulatory Rab-GTPases associated with this compartment in cancerous breast epithelial cell lines was performed using Airyscan microscopy and 3D rendering approaches. This analysis showed that highly aggressive triple negative MDAMB231 breast cancer cells have larger but significantly fewer EEA1-enriched early sorting endosomes compared to non-cancerous MCF10A cells. Furthermore, live-cell time-lapse imaging showed that, despite normal transferrin recycling, the epidermal growth factor (EGF) and transferrin are found together in these large endosomal vesicles following internalization in MDAMB231 but not in MCF10A cells. Most importantly, these large EEA1-positive MDAMB231 endosomes exhibited prolonged EGF-induced activation of EGFR (p1068). We investigated the role of Rab4-mediated changes on endosome structure and function and found that over-expression of wild-type Rab4 in non-cancerous MCF10A cells produced similar EEA1-positive enlarged early-endosomes with prolonged EGF induced EGFR activation (p1068). Rab4 mutants in dominant-negative or constitutively-active state did not elicit the same effects as the wild-type Rab4, indicating that the on-off cycling of Rab4 is critical for the regulation of endosomal size and number. These large endosomes contain adjacent Rab4 and Rab11 domains, are located primarily at the perinuclear region and can undergo actin-associated budding events to recycle cargo out towards the plasma membrane. Altogether, this extensive characterization of early-endosomes in breast cancer cells has identified a novel Rab4 regulated enlarged endocytic compartment leading to prolonged EGFR activation. Interestingly, our data suggests that a population of “pre-existent” large EEA1-containing endosomes is present in some breast cancer cells, challenging the current views of endosome biogenesis. This research is essential to determining receptor regulation in translational breast cancer models which can impact the optimization of anti-cancer human therapies. Alterations in endocytic regulation in cancer cells may be key to understanding the adaptability of cancer cells and lead to new therapeutic targets. Support or Funding Information This work was supported by the National Institute of Health (NIH) R01 BRG CA20772 Breast cancer cells have altered early-endocytic morphology Representative images from whole-cell Airyscan microscopy assay to quantitatively characterize early-endocytic morphology (with respect to whole-cell morphology) in non-cancerous breast epithelial cells (MCF10A)and breast cancer cell lines (MDAMB231 and T47D) with 3D rendering techniques. Example image from live-cell 4D imaging of endosomal dynamics that facilitates our comprehensive characterization of Rab4-regulated endosomes in breast cancer cells. Prolonged EGF-induced EGFR activation (p1068) in MDAMB231 compared to MCf10A This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 60: Ischemic Conditioning Improves Brachial Artery Flow Mediated Dilation in Chronic Stroke Survivors

Introduction: Brachial artery flow mediated dilation (FMD) is a well-established measure of vascular endothelial health and is pathologically low in chronic stroke survivors. Ischemic conditioning (IC) is a cardioprotective stimulus and has been shown to improve FMD and enhance motor function in healthy humans. We recently showed that IC can improve paretic muscle strength and increase self-selected walking speed in stroke survivors. These improvements could be, in part, mediated by improved peripheral vascular function and increased blood flow to the exercising muscle. The effects of IC on vascular endothelial function post-stroke have not been investigated. Hypothesis: Two weeks of IC on the paretic leg of chronic stroke survivors will improve FMD in the non-paretic brachial artery. Methods: This was a prospective, randomized, blinded and controlled pilot study. Twenty chronic stroke survivors (>1-year post-stroke) received either IC (cuff inflation on the paretic leg for five minutes to 225 mmHg) or Sham IC (cuff inflation to 10 mmHg) every other day for two weeks (five on-off cycles per session). Brachial artery FMD was assessed using ultrasonography within 48 hours of the beginning and end of the intervention period. Results: Eight men and twelve women participated in this study. The mean age was 59 ± 16 years and the mean time post-stroke was 9 ± 9 years. Brachial artery FMD increased in the IC group from 6.2 ± 4.9% to 8.9 ± 3.9% (n=10; p=0.023, 2-way Repeated Measures ANOVA) while no change was observed in the Sham IC group (pre- vs. post = 3.8 ± 3.9% vs. 2.7 ± 3.1%, respectively; p=0.32, n=10). Expressed as the mean change in FMD, IC increased FMD by 2.8 ± 3.7% while no change was observed in the Sham IC group (delta FMD = -1.1 ± 3.4%; p=0.024 IC vs. IC Sham, unpaired t-test). Conclusions: Two weeks of IC increases brachial artery FMD in chronic stroke survivors. Taken together with our previous work that shows IC increases paretic muscle strength and walking speed in chronic stroke survivors, IC has the potential to improve both motor and cardiovascular function post-stroke. Future larger studies are needed to evaluate the efficacy of IC to improve stroke recovery and to identify the pathways involved which confer benefit to both the nervous and cardiovascular systems.

Investigation on Ternary Salt-Water Solutions as Phase Change Materials for Cold Storage

Cold storage attracts increasing interest in applications where cooling can be generated more efficiently or in different locations. Phase change materials (PCM) which have high thermal storage capacity are promising materials that can be used to maintain product temperature within safe limits during frequent door openings, on-off cycling of the compressor and power shut off or failure. This study considered candidate phase change materials for application in freezers for product temperature range below -17 ℃. The latent heat and phase change temperature of different ternary salt-water systems with different salt combinations and concentrations have been measured to find suitable eutectic material, which has proper phase change temperature and high latent heat of fusion for applications.

Self-powered lead-free quantum dot plasmonic phototransistor with multi-wavelength response

Because they possess excellent visible light absorption properties, lead-free colloidal copper-based chalcogenide quantum dots (QDs) have emerged in photoelectronic fields. By means of localized surface plasmonic resonance (LSPR), the absorption properties of QDs can be enhanced. In this paper, we fabricate a lead-free CuInSe2 QD field effect phototransistor (FEpT) by utilizing the LSPR enhancement of Au nanoparticles (NPs). The plasmonic FEpT demonstrates responsivity up to 2.7 μA·W−1 and a specific detectivity of 7×103 Jones at zero bias under illumination by a 532 nm laser, values that are enhanced by approximately 200% more than devices without Au NPs. Particularly, the FEpT exhibits a multi-wavelength response, which is photoresponsive to 405, 532, and 808 nm irradiations, and presents stability and reproducibility in the progress of ON–OFF cycles. Furthermore, the enhancement induced by Au NP LSPR can be interpreted by finite-difference time domain simulations. The low-cost solution-based process and excellent device performance strongly underscore lead-free CuInSe2 QDs as a promising material for self-powered photoelectronic applications, which can be further enhanced by Au NP LSPR.

Fe2O3 as an efficient filler in PVDF-HFP based polymeric electrolyte for dye sensitized solar cell application

Fe2O3 was synthesized by chemical precipitation method and used as filler in PVDF-HFP based polymer electrolyte for dye sensitized solar cell (DSSC) applications. The plasticized polymer membrane was developed by simple solution casting method with incorporation of Fe2O3 where propylene carbonate was used as plasticizing agent. Structural confirmation of synthesized Fe2O3 powder and crystallinity studies prepared polymer membrane with different weight% of Fe2O3 was studied by the X-ray diffraction analysis. Fourier transform infrared studies of polymer membrane are done to study nature of polymer. Fe2O3 incorporated PVDF-HFP based polymer electrolyte showed ionic conductivity of 6.36 × 10−4 S/cm and diffusion coefficient was found to be 1.02 × 10−6 cm2/s. Furthermore, the electrochemical impedance spectroscopy analysis has been done to study interfacial resistance. The prepared polymer electrolyte (2 wt% filler in PVDF-HFP based) was used in DSSC fabrication, where calculated power conversion efficiency was 3.62% with the enhancement of 2.1 times when compared to pure PVDF-HFP electrolyte. The photocurrent stability of the device under several light on-off cycles is proved via chronoamperometry study. In addition, variation of power conversion efficiencies as a function of time has also been analyzed.

CH3NH3PbBr3 quantum dots for visible wavelength photodetector applications

Perovskite halide materials with their salient optoelectronic features such as high absorption coefficient, large charge carrier diffusion lengths and low carrier recombination, have revolutionised the field of photodetectors. In this paper we report the synthesis of CH3NH3PbBr3 quantum dots for visible wavelength photodetector applications. Quantum dots of size 2–4.5 nm were obtained. UV–Vis and photoluminescence spectroscopy revealed an optical band gap of 2.3 eV. An electrochemical band gap of 2.09 eV was obtained using cyclic voltammetry. CH3NH3PbBr3 quantum dots based visible wavelength photodetector device was fabricated. The time dependent photoresponse was found to be stable over several ON–OFF cycles of the lamp. We have achieved a responsivity, external quantum efficiency and specific detectivity of 6.11 A W−1, 1380.2% and 3.81 × 1012 Jones under AM 1.5 G, 1 sun illumination.