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A facile one-step non-contact process was developed for preparing the substrates for Fabry-Perot-based side-polished optical fiber sensors. A carbon dioxide (CO 2) laser cladding removal technique was used to control the profile of the polished fiber surface and to introduce two reflective cavities. The substrates were characterized for a range of cavity lengths and their thermal response was studied. This device added a degree of freedom to the design of optical fiber based Fabry-Perot sensors and its potential was demonstrated by coating the substrate with polydimethylsiloxane (PDMS). The resulting sensors had a three-order of magnitude increase in sensitivity when compared to the substrate. The polished flat surface provided a route for the integration of novel materials for sensing applications, particularly those where polarization control was vital for light-matter interaction, for example, low dimensional materials such as graphene or MXene. The inherent simplicity, mechanical stability, and scalability of this approach are important steps for the realization of practical devices of this type. [Display omitted] • The in-fiber resonator and side-polished fiber were fabricated with a CO 2 laser in one single step. • The large evanescent field of the side-polished fiber treated with 2D PDMS induced a change in the effective refractive index. • The FPIR-PDMS demonstrated excellent sensitivity, with the dip wavelength shifting by 1.27 nm/℃. [ABSTRACT FROM AUTHOR]

Currently, the development of single-phase white emitters is an interesting research topic. Researchers have paid much attention to tune white-emitting of Dy3+-activated phosphors via Tm3+ sensitization strategy. However, the role of Tm3+ sensitization on luminescence thermostability was usually underestimated. Herein, color-tunable germanate phosphors Ba 2 Y 2 Ge 4 O 13 (BYGO):Tm3+,Dy3+ were prepared. The white light emission is achieved due to the effective energy transfer from Tm3+ to Dy3+. A BYGO:Tm3+,Dy3+-based w-LED exhibits warm white-emitting. Moreover, the back-energy transfer of Dy3+→Tm3+ contributes to the improvement of luminescence thermal stability. Meanwhile, the difference of temperature-dependent Tm3+ and Dy3+ emissions realizes satisfactory temperature sensing properties. This work provides a deep understanding for the role of Tm3+ sensitization strategy on color tuning and thermostable improvement, promoting multifunctional utilizations of Dy3+-activated phosphors. [Display omitted] • BYGO:Tm3+,Dy3+ achieves white light emission due to the effective ET from Tm3+ to Dy3+. • Excellent luminescent thermal stability comes from the Dy3+→Tm3+ BET. • The title phosphor exhibits excellent temperature sensing properties. [ABSTRACT FROM AUTHOR]

The effects of carbon nanoparticle (CNP) on rice variety Swarna (MTU7029) were investigated. CNP induced effects similar to shade avoidance response (SAR) of Arabidopsis , with increase in shoot length, root length, root number, cotyledon area, chlorophyll content and total sugar content in rice seedlings. In mature plants, CNP treatment resulted increase in plant height, number of productive tillers per plant, normalized difference vegetation index, quantum yield and root growth. A total of 320 mg of CNP per plant administered in four doses resulted in improved grain traits such as filled grain rate, 100-grain weight, grain length/width ratio, hulling rate, milling rate and head rice recovery. Seeds from the CNP-treated plants showed increase in amylose, starch and soluble sugar contents compared to controls. Strikingly, CNP treatment showed an average of 17.5% increase in yield per plant. Upon investigation to the molecular mechanism behind CNP induction of SAR, a significant downregulation of phytochrome B transcript was found. Decrease in perception of red wavelengths led to responses similar to SAR. Increase in plant's internal temperature by 0.5 °C ± 0.1 °C was recorded after CNP treatment. We suggest that the internalized CNP aggregates may serve to absorb extra photons thereby increasing the internal temperature of plants. Phytochrome B accounts the hike in internal temperature and initiates a feed-back reduction of its own transcription. We suggest that moderate SAR is beneficial for rice plants to improve agronomic traits and yield. It presents a potential non-transgenic method for improving rice yield by CNP treatment. [ABSTRACT FROM AUTHOR]

Real-time monitoring of temperatures over extensive free-form surfaces of precision machines, smart products, and human bodies with a high resolution can provide invaluable information for smart manufacturing, Internet-of-Things, and advanced healthcare. However, traditional rigid thermistors could not be conformally attached on arbitrarily curved surfaces. In this study, a high-resolution flexible graphene thermistor is demonstrated by transforming wood into laser-induced-graphene via ultrafast laser pulses and subsequent transfer to flexible substrates. This thermistor provides a 16-times higher resolution than the state-of-the-art counterparts which was applied to precise temperature monitoring of an electric motor, glass cup, and human hand. [ABSTRACT FROM AUTHOR]

In this study, an idler light power measurement temperature sensor based on four-wave mixing (FWM) is designed and analyzed experimentally. In the experiments, the FWM effect is realized in a highly nonlinear fiber (HNLF). The FWM conversion efficiency of the proposed sensor is calculated, and its temperature sensing is evaluated by changing the pump wavelengths and the signal light powers. Unlike previous studies on the FWM temperature sensors, this work uses the idler light power as sensing basis. The experimental results show that the output power of the idler light varies significantly with the temperature at different pump wavelengths. In the experiment, a temperature sensor with a measurement range from 20 ℃ to 80 ℃ is used. The results show that at a wavelength of 1540 nm, the average signal light power is 60 mW, and the proposed sensor's sensitivity is 0.1295 dB/℃. The proposed sensor is easy to operate and allows performing measurements conveniently. In addition, it provides an improved measuring method for FWM-based temperature sensing. • This study introduces a temperature sensor based on DFWM idler power in a highly nonlinear optical fiber for the first time. • The results show that the maximum conversion efficiency of −21.36 dB is achieved at a wavelength of 1555 nm, and the maximum tuning range of the entire experiment is 32 nm. • In the experiments, a temperature sensor with a measurement range from 20 ℃ to 80 ℃ is used, and the average power of the signal beam is 60 mW at a pump wavelength of 1540 nm. The sensitivity of the proposed sensor is 0.1295 dB/℃. • The proposed temperature sensing method is suitable for irritating and asphyxiating gas chambers, such as nitrogen oxides, phosgene, hydrogen fluoride, sulfur dioxide, and hydrogen sulfide. [ABSTRACT FROM AUTHOR]

The monitoring of heat flux is becoming more and more critical for many technologies approaching nanometric dimensions. Scanning Thermal Microscopy (SThM) is one of the tools available for thermal measurement at the nanoscale. This measurement technics needs calibration samples. Therefore, micro-hotplates made of platinum heater suspended on thin silicon nitride (SiN) membranes were fabricated for the calibration of Scanning Thermal Microscopy probes. The objective is to obtain heated reference samples with localised resistive temperature sensors (RTD) on the membrane to probe the temperature on a micro-scale area (typically 10x10 μm 2 ). This sensing area is dedicated to (1) quantify the thermal resistance between the SThM tip and hot surface contact; and to (2) evaluate the perturbation induced by the probe on the heat dissipation when the contact measurement is performed. In this communication, we report on the thermal design of low-power calibration chip and their fabrication, as well as the electro-thermal characterization of sensitive RTDs made using e-beam technology. Thermal contact measurements using a thermocouple based SThM probe validated the functionality of the calibration chip. [ABSTRACT FROM AUTHOR]

The monitoring of heat flux is becoming more and more critical for many technologies approaching nanometric dimensions. Scanning Thermal Microscopy (SThM) is one of the tools available for thermal measurement at the nanoscale. This measurement technics needs calibration samples. Therefore, micro-hotplates made of platinum heater suspended on thin silicon nitride (SiN) membranes were fabricated for the calibration of Scanning Thermal Microscopy probes. The objective is to obtain heated reference samples with localised resistive temperature sensors (RTD) on the membrane to probe the temperature on a micro-scale area (typically 10x10 μm 2 ). This sensing area is dedicated to (1) quantify the thermal resistance between the SThM tip and hot surface contact; and to (2) evaluate the perturbation induced by the probe on the heat dissipation when the contact measurement is performed. In this communication, we report on the thermal design of low-power calibration chip and their fabrication, as well as the electro-thermal characterization of sensitive RTDs made using e-beam technology. Thermal contact measurements using a thermocouple based SThM probe validated the functionality of the calibration chip. [ABSTRACT FROM AUTHOR]

We report on exploiting the down-chirp phenomenon seen in quantum cascade lasers (QCLs), when modulated with long pulses, for the purpose of performing calibration-free and temporally resolved measurements. Intrapulse spectra of a native species (e.g., H 2 O), common to combustion environments, were generated near λ = 7.62 μm at repetition rates as high as 3.125 MHz. Two-line absorption spectroscopy was employed to infer calibration-free temperature from the chirp-induced intrapulse spectra. In this study, such temperature measurements were limited to rates of 250 kHz due to spectral distortion at higher repetition rates. We demonstrate the ease at which accurate temperatures and H 2 O compositions can be achieved using simple and compact QCLs operated in the intrapulse mode. The sensor is also applicable to other species, and has the potential to be integrated into commercial technologies. [ABSTRACT FROM AUTHOR]

The paper presents an effect of fiber bending on sensitivity of long-period gratings (LPGs) to temperature and to surrounding refractive index (RI). The LPGs were manufactured by UV-exposure of hydrogen-loaded Corning SMF28 fibers and their annealing was followed by wet etching in hydrofluoric acid up to dispersion turning point (DTP) where the LPG shows the highest sensitivity. The LPGs were subjected to curvatures in range 0.8 to 4.8 m -1 when their temperature (T=20-100 °C) and refractive index (RI) responses (n D =1 to 1.47) were measured. Bending sensitivity reaching 54 nm/m -1 has been obtained. It has been found that as a result of bending, coupling to asymmetrical cladding modes takes place. It results in the resonances increasing their depth and shifting towards longer wavelengths with bending. The bending effect also allows for post-fabrication tuning of the LPGs working at DTP. The LPGs with bending-modified temperature sensitivity up to 0.54 nm/°C have been shown. The method can also be applied for tuning of RI sensitivity of the LPGs. [ABSTRACT FROM AUTHOR]

Optical sensors offer important advantages for sensing applications, compared to their electronic counterparts. These include electrical passiveness and insensitivity to electromagnetic interference. Of considerable interest are large two-dimensional arrays of optical sensors, fabricated in polymers using printing techniques. We describe here the design of waveguide-Bragg-grating-based temperature sensors, fabricated by replication technologies. In contrast to silica fibers, thermal sensitivity of polymeric waveguide Bragg gratings is strongly dependent on the chemical and physical material properties. We introduce simulation results for waveguide and grating design and describe major differences between silica-based and polymeric waveguides with respect to their thermal expansion and thermo-optic coefficients. [ABSTRACT FROM AUTHOR]

Abstract: A two-wavelength mid-IR laser is used for time-resolved absorption-based measurements of temperature and n-heptane concentration in shock-heated gases. The novel difference-frequency-generation laser provides tunable mid-IR light from nonlinear conversion of near-IR light, enabling access to the strong hydrocarbon absorption bands between 3.3 and 3.5μm associated with the Cing vibration. This laser was modified to alternate between two mid-IR wavelengths at 200kHz, providing 5μs time resolution for simultaneous monitoring of temperature and concentration in reactive flows and combustion systems. Temperature-dependent absorption spectra of n-heptane are first measured in a cell from 298 to 773K using an FTIR spectrometer. These spectra are used to select candidate pairs of wavelengths with good sensitivity to temperature and concentration and to provide accurate temperature-dependent absorption cross-sections at the selected wavelengths. Laser absorption measurements of shock-heated n-heptane are then used to extend the cross-section data to 1300K and to investigate the sensor accuracy and noise characteristics. The temperature and concentration inferred from the measurements are compared to known post-shock conditions, with a 4.5% RMS deviation from the calculated temperature and 1.7% RMS deviation from the calculated concentration. Finally, at high temperatures, the sensor is used to monitor decomposition of n-heptane, illustrating the potential of this diagnostic for hydrocarbon kinetics experiments in shock tubes. This new sensor concept should prove useful for simultaneous, time-resolved temperature and hydrocarbon concentration measurements in a variety of combustion and propulsion applications. [Copyright &y& Elsevier]

Abstract: A novel tunable diode laser temperature sensor is used to prevent lean blowout (LBO) in a swirl-stabilized, partially premixed dump combustor which serves as a model of gas turbine combustors. The fast-response temperature sensor is based on rapid, repetitive (2kHz) wavelength-scanned laser absorption of two vibrational overtone transitions of water vapor near 1.4μm using a single fiber-coupled diode laser. Although the gas composition and temperature are not uniform along the line-of-sight, low-frequency temperature fluctuations are identified in the FFT power spectrum of the real-time temperature measurements at an optimized location. We found that the fraction of the FFT power at low-frequencies (0–50Hz) increases exponentially as the flame approaches LBO. The intensity of these low-frequency temperature fluctuations is used to detect the proximity to LBO and as a control variable for the active LBO control system. Successful prevention of LBO during power reduction and transient fuel variation is demonstrated even without knowledge of the LBO fuel/air ratio limit for the specific operating conditions of the combustor. The active control system also can maintain the flame at very lean conditions (0.03 above the LBO equivalence ratio), and thus reduce the LBO margin. To our knowledge, this is the first application of laser-based sensors in active LBO control of swirl-stabilized flames. The results demonstrate the potential of tunable diode laser sensors for closed-loop combustion control applications. [Copyright &y& Elsevier]

In this paper, to achieve a high-precision temperature sensing, a modified anapole resonator based on the liquid–metal (Hg) with high Q-factor and large thermal-sensitivity properties is proposed. The high-Q resonance of the designed Hg-anapole resonator is excited by a simple microstrip coupling line with large electromagnetic energy coupling rate. The detailed numerical optimization and experimental demonstration are discussed, and the measured temperature sensitivity of 17.14 MHz/°C and figure-of-merit (FOM) of 0.3/°C are achieved based on the proposed Hg-anapole resonator. This kind of liquid high-Q metamaterial unit can be widely used to realize the high-precision sensing. [ABSTRACT FROM AUTHOR]

• The GH shifts in SGCW present a quasi-periodic tendency with change of temperature. • We propose a high-sensitivity temperature sensing scheme based on GH shifts in SGCW μ. • Our scheme has advantages of high sensitivity, label-free and resisting interference. We theoretically investigate the temperature-dependent Goos-Hänchen (GH) shifts in a symmetrical graphene-cladding waveguide (SGCW). The GH shifts in SGCW present a quasi-periodic tendency near the resonance angle with the change of temperature, which can mainly be attributed to the temperature dependence of the guiding layer's thickness, instead of the graphene intraband conductivity and guiding layer's refractive index. Importantly, tiny temperature fluctuations can cause significant deviations in GH shifts, and the deviations can be efficiently improved by adjusting the Fermi energy. Therefore, we propose a high-sensitivity temperature sensing scheme based on GH shifts in the SGCW, and the maximum sensitivity can reach up to −2.2 × 105 μ m/ ° C. These researches may open avenues for applications of optical temperature sensors. [ABSTRACT FROM AUTHOR]

• We propose an approach to infer ambient temperature using on-device machine learning approach that leverages mobile phone battery temperature. Further, we use an opportunistic crowdsensing based approach that aggregates the readings across phones at a location and computes an ambient temperature reading based on the designed policies. • We highlight the challenges in efficient HVAC scheduling that increases the energy-efficiency while simultaneously improving user comfort. • We propose a data-driven on-device machine learning model for ambient temperature prediction. • We present a mini-batch based transfer learning technique to deploy our model on a never-before-seen phone to avoid the data collection and calibration effort to train our model on new phones. • We design a RESTful web service for crowdsensing indoor temperature measurements and design policies to distinguish high-quality crowd sensed measurements from lower quality measurements. • We evaluate our approach using multiple devices and scenarios and demonstrate the efficacy of our model. Due to the ubiquitous nature of smartphones, opportunistic phone-based crowdsensing has emerged as an important sensing modality. Since fine-grain ambient temperature measurements are a pre-requisite for energy-efficient operation of heating and cooling (HVAC) systems in buildings, in this paper, we use mobile phone sensing in conjunction with a web-based crowdsensing system to obtain detailed ambient temperature estimates inside buildings. We present a machine learning approach based on a random forest ensemble learning model that uses the phone battery temperature sensor to infer the ambient air temperature. We also present a few-shot transfer learning method to quickly learn and deploy our model onto new phones with modest training overheads. Our crowdsensing web service enables predictions made by multiple phones to be aggregated in an opportunistic fashion, extending our approach from an individual level to a community level. We evaluate our ML-based model for a range of devices, operating scenarios, and ambient temperatures, and see mean errors of less than ± 0.5 ° F for our temperature predictions. More generally, our results show the feasibility of using an on-device ML model for ambient temperature predictions in mobile phones. This allows buildings – new and old, with and without sensing systems – to benefit from a new class of ubiquitous temperature sensors, enabling more sustainable operation. [ABSTRACT FROM AUTHOR]

The phonon behavior of various Ge-based samples has been investigated in great detail. The study comprised Ge films (amorphous and partially crystallized and alloyed with oxygen), crystalline Ge wafers (pristine and alloyed with oxygen), and GeO 2 powder. The oxygen-containing samples obtained after thermal annealing the Ge film and Ge wafer correspond to sub-stoichiometric GeO 2 , or the so-called Ge + GeO x system, in which case [O] ∼40 at.%. A thorough examination of this Ge + GeO x system – as provided by temperature-dependent Raman scattering, their analysis according to the existing theoretical models (involving anharmonic phonon coupling and thermal expansion processes), and a critical review of the literature – indicates the coexistence of practically independent Ge–Ge- and Ge–O-related structures and confirms the presence of both structural and chemical (dis)order. Moreover, the main features regarding the phonon frequencies (ω), line widths (γ), and scattering intensities (I S) of the Ge + GeO x system suggest their suitability in temperature sensing applications. Accordingly, experimentally determined reference curves (i.e. , ω T , γ T , and I S T data described in terms of simple mathematical functions) gave rise to temperature accuracies on the order of 20 K. Everything considered, in its current form, this work presents the first comprehensive analysis-discussion regarding the Ge + GeO x system that, additionally, is being proposed as an effective medium for optical thermometric applications. [ABSTRACT FROM AUTHOR]

The upconversion nanoparticles (UCNPs) exhibit versatility applications aiming at biological domains for decades on account of superior optical characteristics. Nevertheless, the UCNPs are confronted with tremendous difficulties in biological field owing to large grain size, low fluorescence efficiency, and single function. Herein, the small-sized CaF 2 : Yb3+/Er3+ UCNPs coated with NaGdF 4 shells (activator and inert, UCNPs-RBHA-Pt-PEG) not only burst out strong fluorescence, but also provide prominent diagnosability by taking advantage of magnetic resonance (MR) imaging as well as temperature sensing and inhibiting capability for CT26 tumor tissues based on synergetic therapy modality of photodynamic therapy (PDT) and chemotherapy. Ultimately, the tumor sizes decrease visibly after injected with UCNPs-RBHA-Pt-PEG and simultaneously irradiated with near infrared (NIR) light at low power density (0.35 W/cm2, 6 min). In summary, the small-sized and strong-fluorescent single nanoparticles with multi-functions may provide a valuable enlightenment for diagnosis and treatment of cancer in the future. The small-sized and enhanced-fluorescent CaF 2 UCNPs emit strong fluorescence after coated with NaGdF 4 shells (activator and inert). The ample PDT efficacy is achieved relied on the fluorescence resonance energy transfer owing to a large overlap between upconversion emission and rose-bengal hexanic acid absorption (UCNPs-RBHA). At the same time, the UCNPs-RBHA conjugated with platinum (IV) and polyethylene glycol possesses high cell apoptosis for the CT26 cells due to high endocytosis. The UCL and MR imaging, temperature sensing, and strong antitumor effect based on the synergetic therapy of PDT and chemotherapy are achieved on the single nanoparticles. Unlabelled Image [ABSTRACT FROM AUTHOR]

The recent progresses on smart technology and on Internet of Thing (IoT) have created a huge demand on development of cost-effective and environment friendly alternate energy sources, by using light weight, low cost, flexible and easily available materials. However, in this work, a new type of triboelectric driven flexible and self-charging triboelectric power cell (STPC) has been fabricated by using commercially available materials, namely bulk MoS 2 , non-conductive glue, graphite powder, and normal sheet of paper. Interestingly, STPC exhibits excellent output performances with the maximum power, open circuit voltage (V oc), and short circuit current of ~0.67 μW, ~3.82V, and ~0.20μA, respectively under a periodic pressure of amplitude of 1 kPa. The V oc of the fabricated device is found to be highly sensitive and showed linear response to number of folding (N), externally applied weight (W), and temperature (T). For instance, dV oc /dT and dV oc /dW of STPC is found to be 0.093VK-1 and 0.2Vkg-1 in temperature and weight range of 293–323K and 50–72kg, respectively. Further, we have calculated the figure of merit of the developed device by calculating the values of relative sensitivity coefficients (S) of V oc w.r.t. N , W , and T and the highest obtained values of S are ~1.12, ~4.35, and ~16.00, respectively. The reported simple method of development of paper based STPC cell, based on only commercially available materials, can be utilized further for development of flexible, light weight, low cost and eco-friendly wearable sensing devices. Image 1 • New type of triboelectric driven flexible STPC has been fabricated on a normal sheet of paper. • The STPC exhibits P max , V oc , & I sc of ~0.67 μW, ~3.82 V, & ~0.20 μA, respectively in 1 kPa impact. • V oc of STPC shows linear responses to number of folding, externally applied weight, & temperature. • d V oc /dT of the STPC is found to be 0.093VK-1 in the temperature range of 293–323 K. • V oc of STPC is increased linearly with externally weight up to 72 kg. [ABSTRACT FROM AUTHOR]