The understanding of interactions between electrons and phonons in atomically thin heterostructures is crucial for the engineering of novel two-dimensional devices. Electron–phonon (el–ph) interactions in layered materials can occur involving electrons in the same layer or in different layers. Here we report on the possibility of distinguishing intralayer and interlayer el–ph interactions in samples of twisted bilayer graphene and of probing the intralayer process in graphene/h-BN by using Raman spectroscopy. In the intralayer process, the el–ph scattering occurs in a single graphene layer and the other layer (graphene or h-BN) imposes a periodic potential that backscatters the excited electron, whereas for the interlayer process the el–ph scattering occurs between states in the Dirac cones of adjacent graphene layers. Our methodology of using Raman spectroscopy to probe different types of el–ph interactions can be extended to study any kind of graphene-based heterostructure. Electron–phonon interactions in van der Waals layered materials can occur either within the same layer  or in different layers (interlayer). Here, the authors use multi-wavelength Raman spectroscopy to probe intra- and inter-layer electron–phonon interactions in twisted graphene heterostructures. For twisted bilayer graphene (TBG), the interaction between electrons of different layers generates van Hove singularities (vHs) in the density of electronic states (DOS), whose energies are θ dependent3. Electron–phonon coupling is also a fundamental interaction that affects a broad range of phenomena in condensed matter physics, such as electron mobility and thermal conductivity. In atomically thin heterostructures, the interaction can involve electrons in the same layer  or in adjacent layers (interlayer el–ph interaction). The interlayer el–ph interaction has been recently observed in WSe2/h-BN heterostructures4.Interlayer electron–electron and electron–phonon (el–ph) scattering processes emerge from the coupling of atomic layers in two-dimensional (2D) heterostructures, and are essential for describing their physical properties and technological applications. The additional possibility of controlling the twisting angle θ. Prominent new peaks are observed in the Raman spectra of TBG samples and come from phonons within the interior of the Brillouin zone (BZ) of graphene that are folded to the centre of the reduced Moiré pattern BZ. The frequencies of these phonons depend on the twisting angle θ11. We show here that they can be activated either by the intralayer or the interlayer processes. The intralayer process was also observed in the Raman spectra of gr/h-BN samples and allows the experimental determination of their mismatch angle between the crystallographic axes of graphene and h-BN. In this case, the el–ph process occurs in a graphene monolayer and the h-BN surface imposes a periodic potential needed for the electron backscattering in the resonant Raman process. This effect is expected to be sensitive to the strength of the interaction between monolayer graphene and any other single layer or crystalline surface.Here, we report the ability of Raman spectroscopy to probe and distinguish interlayer and intralayer el–ph interactions in graphene heterostructures. This is experimentally attained by tuning the energy of the excitation photon and observing the resonances of the Raman modes in different samples of TBG and graphene on the top of h-BN (gr/h-BN), with previously determined mismatch twisting angle θ can be determined from the optical images using the procedure reported in ref. 12 . The ratio of ITBG/ISLG = 1.8 eV for the G-band intensity (around 1580 cm−1) of the θ = 6° sample shown in Fig. 12. However, for the θ = 13° sample shown in Fig. ITBG/ISLG is more than 50. This huge increase of the G-band intensity has already been observed in previous Raman studies of TBGs16 and explained by the resonance of the incident photons with the transition between vHs in density of electronics states of a TBG.Experiments were first conducted in TBG flakes, that appear in an optical microscope as an external hexagon (first layer) and an internal one (with two layers), where the twisting angle −1. Extra peaks have been observed in many previous Raman studies of TBGs11. They arise from phonons of graphene with momentum ħqM, where qM is a vector of the Moiré pattern reciprocal lattice, that are folded to the centre of the reduced BZ and become Raman active11. In 2010, Gupta et al.5 proposed that the extra peaks were activated by double-resonance Raman (DRR) process where momentum conservation is provided by the potential of the Moiré reciprocal lattice. Carozo et al.7 attributed the new peaks below and above the G-band position to the intervalley and intravalley DRR processes, and estimated the resonance energies as a function of θ for these two processes. The valleys considered in this work belong to the same graphene layer and, therefore, both cases correspond to an intralayer el–ph scattering process.In addition to the G band, we can observe in Fig. 10 and Wang et al.11 reported measurements of TBG samples with intermediate twisting angles (13°–16°) using different laser lines. In both works, the appearance of new peaks in the range 1380–1450 cm−1 was observed to occur in the same spectra where the G band was enhanced. This resonance behaviour could not be explained by the predictions of the DRR process involving the periodic potential of the Moiré7, and revealed that a different el–ph process involving phonons with momentum ħqM may exist. We will show below that the new phonons observed in these works11 are activated by the interlayer el–ph scattering process.In 2013, Carozo et al.R and R′ peaks10. Since they can be activated either by the intralayer or the interlayer el–ph scattering process, we will adopt for these peak notation Aα, where A = T or L refers to the branch  of the unfolded phonon and α refers to the el–ph scattering mechanism . It will be clear below that the extra peaks above and below the G band shown in Fig. a and Te, respectively.The extra peaks below and above the G-band position have been called in the literature as the θ = 6 and 13°, respectively. The vertical scale corresponds to the energy of the incident photon, and the peak intensities are represented by the colour bar on the right side. We can observe in Fig. ITBG/ISLG of the θ = 6° sample does not depend on the photon energy and is always around 1.8, an expected value far from resonance conditions12. On the other hand, the La peak clearly exhibits a resonance behaviour and reaches the maximum intensity for photon energies around 2.2 eV, where it becomes as intense as the G band in SLG. Figure θ = 13° sample exhibit a different behaviour. Now, both the G band and the Te peak exhibit a resonance behaviour and are enhanced in the same excitation energy range.In order to explain the different resonance behaviour of the Raman peaks in TBGs, we first made multiple-excitation Raman measurements using many different laser lines in the visible range (see Methods section), which allowed us to obtain the accurate Raman excitation profile (REP) of Raman peaks in samples with small and intermediate twisting angles. Figure a and Te peaks, that is, the intensity of each peak as a function of the photon energy, for the θ = 6 and 13° samples, respectively. Figure a peak exhibits maximum enhancement at approximately 2.2 eV and has a width γ around 0.7 eV. This value of γ agrees with the result in a previous ultraviolet (UV) Raman study of TBGs8. In the case of the θ = 13° sample shown in Fig. e peak exhibit very similar REPs, except for the fact that the intensity of the extra peak was multiplied by ≈ 100 for comparison. The data in Fig. 10, where the fitting parameters are the energies of the optical transitions among vHs, EvHs, and the width γ of the REP. The values of the parameters that fit the experimental data in Fig. EvHs = 2.37 eV and γ = 0.25 eV. Notice that this value of γ agrees with the width of the peaks in the optical absorption spectra of TBGs17. Several other samples with low (4°–6°) and intermediate (12°–16°) twisting angles were investigated using multiple-excitation Raman measurements, and results similar to those shown in Fig. EvHs and γ for the G band on the twisting angle θ is shown in ref. 18.Figure ħqM to another state in the same layer , whereas in the other case, the excited electron is scattered to a state of the other layer (interlayer process). We will show that these two mechanisms give rise to resonances at different energies.In order to understand the origin of the results presented above, we performed a theoretical simulation considering two different el–ph processes that take part in the Raman scattering. Details of the calculations are given in the Methods section. In one case, the excited electronic state from one layer is scattered by phonon with momentum θ = 13.2° and represented, respectively, by the grey and black hexagons. The vectors q1, q2 and q3 correspond to the unit vectors of the Moiré reciprocal lattice (we will consider in this work that qM = q1 or q2 or q3). The reduced BZ of the Moiré superlattice is shown by the small red hexagon in the centre of Fig. θ = 13.2° TBG and shown in Fig.Ea  creates an electron–hole pair, and a phonon with momentum ħqM  scatters the excited electron to another state in the same Dirac cone (layer B in this case). For simplicity, the change in energy between these two states is not considered in this figure since the phonon energy is much smaller than the energy of visible photons. In the interlayer process also represented in Fig. Ee creates one electron–hole pair, but now the electron from one layer (layer B) is scattered to a state of the other layer (layer A) by a phonon with momentum ħqM. In both cases, the electron is then scattered back elastically to the first excited state by the Moiré potential, with wave vector qM, for electron–hole recombination and emission of the scattered photon.Figure Ee around the Dirac points KB and KA, respectively. An excited electron with momentum ħk from the Dirac cone of one layer (dark green curve) is scattered by a phonon with momentum ħqM (red arrows) to a state with momentum ħk′ in the Dirac cone of the other layer (light green curve). The lowest possible value of Ee occurs when the equi-energies curves of the two layers tangentiate, as shown in Fig. Ee, the difference EvHs between the vHs in the valence and conduction bands of a TBG.Figure A and KB, respectively, correspond to the curves of constant energy Ea. In this case, the excited states with momenta ħk and ħk′ belong to the Dirac cones of the same layer (dark or light blue curves). The intralayer process is similar to the DRR mechanism that gives rise to the disorder-induced D and D′ bands in the Raman spectrum of graphene19. For the disorder-induced bands, the electron is scattered back to the initial excited state by a defect whereas, in the case of TBG, the backscattering is provided by a periodic potential of the Moiré pattern. This DRR process, where momentum conservation is provided by a vector qM of the Moiré lattice, has been called previously as the umklapp DRR process6.The intralayer el–ph scattering process is schematically represented in Fig. qM. In the reduced BZ scheme, they are folded to the centre of the reduced BZ and have zero momentum. The first-order Raman process can be accomplished in this scheme since the two excited states k and k′ in the extended BZ in Fig. k and k′ in the extended BZ in Fig. So far, we discussed the two processes in the extended BZ scheme, where the activated phonons have finite Ea and Ee, we calculated the restricted density of joint electronic states that satisfy the intralayer and interlayer conditions. For the calculation, we divided the graphene BZ in a 2400 × 2400 k-points grid and, for each twisted angle θ, we stored the number of joint electronic states satisfying the restriction α symbolises the valence or the conduction bands and ε = 0.02 eV is an arbitrary tolerance. For the intralayer case, we have k′ = k + qM because the two electronic states, k and k′, are connected by qM while for the interlayer process, k′ = R(θ)k + qM, where R(θ) is the rotation matrix that takes the Dirac cone of one layer into the Dirac cone of the other layer. Considering these two conditions, momentum conservation is always achieved in our model by a given pair of states, k and k′, as shown in Fig. In order to determine the resonance energies θ. The position of the low-energy peaks increases, whereas the position of the high-energy peaks decreases with increasing values of θ. These two maxima are associated with electronic transitions close to K and M points of the graphene, and will be called E− and E+. For the intralayer process, the positions of EvHs.Figure θ represented by the dashed blue, green, pink and red curves, respectively. In Fig. −1 that are observed in samples with small angles (4°–6°). They nicely agree with the calculated Ea versus θ results represented by the dashed blue curve. Details about the experimental values are shown in Supplementary Note −1 for samples with intermediate twisting angles (12–16°) are plotted as open black circles in Fig. θ. The black symbols × in Fig. EvHs measured directly by optical conductivity17. It is interesting to note that, despite the fact that our model does not consider electronic coupling between the layers that opens a minigap which splits the valence and the conduction bands in TBL, the agreement between the minimum possible value 17 is remarkable.Figure ħqM as a function of θ. The frequencies of the extra peaks of samples with small (intermediate) values of θ are plotted as open blue (black) circles in Fig. The red and black curves in Fig. a and Le peaks for samples with intermediate angles. However, Ta and Le were not observed in our multiple-excitation experiments using visible photons. The lack of observation of Le can be due to the huge enhancement of the G band. Since the position of the Le peak is very close to the G-band position in samples with intermediate twisting angles, it is possibly masked by the G-band enhancement. For samples with θ around 10° and measured using the 1.96 eV laser line, Campos-Delgado et al.9 reported the observation of a peak at 1622 cm−1, that might be assigned to the Le. The absence of Ta can be ascribed to the very weak cross-section of TO phonons activated by the intralayer process. Electron–phonon matrix elements calculations would be necessary to better clarify this issue.In principle, the intralayer and interlayer el–ph processes can also activate TO and LO phonons, respectively, and give rise to Tθ in the range of 2–9°, using three laser lines with energies 1.49, 1.70 and 1.82 eV  that was not observed in the results obtained with visible photons and shown in Fig. qM tends to zero. The laser energies where the extra peaks observed in the infrared (IR) Raman spectra in samples with θ in the ranges of 3–5 and 6–9° have the maximum intensity are shown, respectively, by the light blue and red open squares in Fig. The calculated results presented in Fig. θ show that extra peaks are expected to appear in the UV Raman spectra (for excitation energies above 3 eV). Figure −1. In the pioneer Raman study of graphene folded onto itself, Gupta et al.5 observed nondispersive extra peaks in the range of 1370–1395 cm−1, and showed that they were enhanced in the UV Raman spectrum (Elaser = 3.41 eV). Righi et al.6 studied the UV Raman spectra of TBGs and observed several extra peaks in the range of 1370–1420 cm−1, but the twisting angles θ were not determined in this work. In both studies6 the appearance of new peaks was not accompanied by the enhancement of the G band, as expected for an intralayer el–ph process. In contrast, the UV data of Wang et al.11 in TBG samples with large values of θ show the activation of new peaks in spectra where the G band also exhibits an enhancement of 5–20 times, indicating thus an interlayer el–ph scattering. The laser energies where the extra peaks of the samples with large values of θ in the range of 22–28° exhibit the largest intensity and the frequencies of these peaks observed in the UV Raman spectra are represented by black open squares in Fig. 11 are also plotted in Fig. The theoretical predictions in Fig. θ = 23, 25 and 28°, performed with the 3.00 and 3.41 eV excitation energies (details are described in the Methods section). The vertical scale gives the ratio of ITBG/ISLG. We can see in the spectra new peaks with frequencies in range of 1370–1420 cm−1, as predicted in Fig. Figure θ = 23° sample recorded with the 3.00 eV line and shown in Fig. ITBG/ISLG for the G band is ≈ 9, suggesting that the two peaks around 1380 and 1410 cm−1 come from phonons of the TO and LO branches, respectively, and are activated by the interlayer el–ph process (Te and Le peaks). On the other hand, in the spectrum of θ = 28° sample recorded with the 3.41 eV line and shown in Fig. ITBG/ISLG ≈ 2 for the G band reveals the activation by the intralayer el–ph process. We thus assign the extra feature around 1370 cm−1 as a La peak, although we cannot rule out the possibility of being a Ta peak, since, as shown in Fig. θ. In Fig. ITBG/ISLG for the G band is around 4 and only one extra peak is observed. In this case, possibly both processes are occurring simultaneously. The peak position around 1380 cm−1 suggests that it comes from a phonon of the TO branch, and it can be thus assigned as a Ta/Te peak. The laser energies where the extra peaks shown in Fig. In the spectrum of the 20 reported the observation of weak extra peaks both below and above positions of the G band in graphene, and suggested that they arise from the graphene/h-BN interaction.As discussed above, the intralayer el–ph process occurs in one graphene layer, and the second layer only imposes a periodic potential needed for momentum conservation in the DRR process. Therefore, extra peaks are also expected to appear in the Raman spectra of graphene deposited on top of any atomically flat substrate, assuming that the interaction graphene/substrate is strong enough to scatter electrons. In a recent study of graphene on the top of h-BN, Eckmann et al.θ 20. They are much less intense than the extra peaks in bilayer graphene showing that the imposed potential of h-BN on graphene is much weaker than graphene–graphene interaction. Results shown in Fig. In order to check this assumption, we prepared graphene/BN samples by transferring SLG to the top of a h-BN crystal. From the analysis of optical images, where the crystallographic edges of graphene and BN are evidenced, we can estimate the twisting angle qM can be activated by two different resonant el–ph processes: the interlayer process, where the electron scattering occurs between the Dirac cones of different graphene layers, and the intralayer process which occurs in a single graphene layer, and the other layer or substrate only imposes a periodic potential that activates the phonons in the Raman spectrum. The observation of new peaks in the Raman spectrum of SLG on the top of h-BN crystals proves that the intralayer el–ph process occurs not only in TBG, but also whenever graphene is in contact with any periodic layer or substrate. The intensity of these extra peaks is expected to provide the strength of the interaction between monolayer graphene and the substrate. On the other hand, the activation of new phonons by the interlayer el–ph process reported in many previous studies in the literature occurs only in TBGs.We report in this work the observation of intralayer and interlayer el–ph interactions in twisted graphene heterostructures with different mismatch twisting angles by Raman spectroscopy. Measurements performed with many different laser excitation energies allowed us to conclude that phonons of graphene with momenta This work highlights the importance of understanding fundamental el–ph interactions in heterostructures of 2D materials, which affect thermal and transport properties in these systems. The possibility of distinguishing intralayer and interlayer el–ph interactions in bilayer graphene and of studying the interaction of monolayer graphene with a crystalline substrate using light scattering allow new ways to design devices applications of 2D heterostructures and is crucial for the engineering of new devices.θ. Experiments in the visible range were performed in a DILOR XY triple-monochromator spectrometer equipped with a N2-cooled charge-couple device detector, a 1800 g/mm diffraction grating, and using an Ar/Kr with 12 laser lines in the visible range. The NIR Raman measurements were performed on a home-made setup, including an iHR-550 Horiba spectrometer equipped with a liquid-nitrogen-cooled silicon CCD detector. A tunable CW Ti:sapphire laser filtered using tunable laser line filters21 was used for excitation. The scattered light was collected through a ×100 objective (NA = 0.95) using a backscattering configuration. The 3.41 eV Raman spectra were obtained using a Dilor UV Raman spectrometer equipped with a cooled CCD and an argon-ion laser. The laser power on the sample was kept lower than 1 mW with ×40 objective to avoid heating. The Raman spectra at 3.00 eV were obtained using a Jobin-Yvon-Horiba T64000 Raman spectrometer equipped with a cooled CCD with a krypton-ion laser. The laser power on the sample was limited to 0.5 mW with ×100 objective. In the case of G/h-BN heterostructures, the measurements were performed in Witec Alpha 300R system using 633 nm as a pump laser.The Raman measurements of the TBG samples were performed using many different laser lines, in the near IR, visible and UV ranges, for samples with different twisting angle 13. The graphene layers were first covered by a thin layer of polycarbonate, followed by etching in HCl aqueous solution to remove the Cu in the transfer process. The polycarbonate film with attached graphene was then transferred onto different substrates: a 300 nm SiO2/Si, 90 nm SiO2/Si and fused silica. Finally, the polycarbonate film was removed using chloroform. The gr/BN samples were prepared by mechanical exfoliation of graphene and transference to a h-BN substrate.The TBG samples were grown by CVD technique using methane (99.99%) on polycrystalline Cu foils22. The electronic structure calculations are based on a tight-binding approach in which the parameters are fitted to reproduce density functional theory (DFT) calculations with many-body corrections, while the phonon dispersion was obtained from many-body corrected DFT calculations. The many-body corrections change the phonon slope of the highest optical branch near K (with respect to DFT), reproducing the Kohn anomaly and providing a much better agreement with inelastic X-ray scattering measurements for graphite23. These curves describe accurately the D band of graphene when a red shift of 40 cm−1 is applied for phonons close to the K point. However, in order to reproduce the phonons close to the graphene G band, we blue shifted all frequencies by 20 cm−1. Even though the calculations were done only by folding the SLG results, the physics of the intralayer and interlayer processes in TBG is nicely captured.The electronic and phonon structures were obtained by folding the SLG calculation results. For SLG, we follow the calculation procedure given in ref. 17. As far as phonon properties are concerned, Cocemasov et al.24 have shown that the weak van der Waals interactions between layers in TBG do not alter significantly the frequencies of the branches in the range considered here. Although the folding method provides a good description of the phonon frequencies and of the electronic transitions of TBG, the theoretical model used here does not give us the intensities of Raman peaks. For that we also need to consider the values of the matrix elements for the el–ph and electron–photon interactions. The computation of these matrix elements can clarify, through the intensity, if the peak marked as Ta/La in Fig. a or La peak.Concerning the electronic properties, it has been shown that interlayer interactions perturb the bands from each layer producing minigaps in the conduction and valence band of TBG with same energy. However, the allowed transitions do not depend on the size of the minigap, and therefore the folding approach is supposed to give good results concerning the Raman processes investigated hereThe data that support the findings of this study are available from the corresponding author upon request.Supplementary Information(PDF 2759 kb)Peer Review File(PDF 261 kb)


Flexible sensors connected to cell phones are a promising technology that can aid in continuously monitoring signals in our daily lives, such as an individual’s health status and information from buildings, farms, and industry. Among such signals, real-time humidity monitoring is crucial to a comfortable life, as human bodies, plants, and industrial environments require appropriate humidity to be maintained. We propose a hydrophilic polytetrafluoroethylene (H-PTFE)-based flexible humidity sensor integrated with readout circuitry, wireless communication, and a mobile battery. To enhance its sensitivity, linearity, and reliability, treatment with sodium hydroxide implements additional hydroxyl (OH) groups, which further enhance the sensitivity, create a strong linearity with respect to variations in relative humidity, and produce a relatively free hysteresis. Furthermore, to create robust mechanical stability, cyclic upward bending was performed for up to 3000 cycles. The overall electrical and mechanical results demonstrate that the flexible real-time H-PTFE humidity sensor system is suitable for applications such as wearable smart devices. The development of flexible humidity sensors has been gaining interest in several applications, including industrial production processes, environmental monitoring, and healthcare ,2,3. MonAmong several types of humidity sensors, the capacitive humidity sensor has been widely investigated because of its capability to function at high temperatures, fully recover from condensation, and resist chemical vapors ,6. CapacMany materials have been studied as dielectric materials for capacitive humidity sensors, including polymers, ceramics, and composites ,9,10. Ce4, with respect to the variation in relative humidity (RH) over a range of 45~90%. In addition, linear behavior of the sensing performance and a low hysteresis were clearly observed. Moreover, the proposed sensor was not significantly sensitive to temperature fluctuations and showed no decrease in performance, even after a cyclic bending test of 3000 cycles. Finally, we implemented a real-time monitoring system through system-level integration of the fabricated flexible H-PTFE humidity sensor with readout circuits and a Bluetooth module. Finally, the proposed system was attached to a curved surface for real-time monitoring of the moisture of the materials, which demonstrates the potential of our sensor as a humidity-monitoring application.In this report, we present a flexible capacitive humidity sensor using hydrophilic polytetrafluoroethylene (H-PTFE) as a dielectric sensitive film for water uptake. H-PTFE is a polymer-based membrane that has a random porous structure with a 0.45 μm pore size and 80% porosity. Due to its porous structure, H-PTFE has a large volume area and flexibility like a paper. In addition, H-PTFE is known to have thermal stability, chemical stability, and tear resistance, which also provide advantages for monitoring sensors . Further−6 Torr. Titanium was used for an adhesion layer in this process. After deposition, the shadow mask was removed. To enhance the mechanical stability of sensors, poly (PET) film (70 µm) was laminated beneath the thin H-PTFE film.The H-PTFE membrane was obtained from Merck Millipore, Burlington, USA. First, the H-PTFE film was prepared with dimensions of 1.5 × 1.5 cm. In order to form the capacitive electrode on the H-PTFE film, a nickel alloy shadow mask  was used for selective deposition of the electrode source. The pattern of the shadow mask was an interdigitated structure with eight fingers. Each finger width was 250 µm and the finger-to-finger distance was 150 µm. The thickness of the shadow mask is 100 μm, which could be adhered completely to the H-PTFE substrate beforemetal deposition. After fixation of the shadow mask above the H-PTFE film, titanium/gold (20 nm/100 nm) was deposited by e-beam evaporator under a vacuum of 10The fabricated H-PTFE humidity sensor was incubated in NaOH solution  for 2 h at room temperature. This process was performed with stirring. After removing the sensor from the NaOH solution, the sensor was dipped into DI water to rinse it enough, then it was dried by nitrogen gas. Finally, the remaining water in the H-PTFE film was completely removed by annealing in a vacuum oven  with a temperature of 120 °C for 1 h. −1.High-resolution field-emission scanning electron microscopy (FE-SEM) images were acquired using Merlin, Carl Zeiss operating at 10 kV. The optical microscope images were obtained by BX51M, Olympus. Fourier transform infrared (FT-IR) spectra were recorded using a Spectrum One system, Perkin-Elmer, with a wavenumber range of 500–4000 cmThe fabricated sensor was connected with wire using conducting tape for electrical measurements. Then, it was inserted in a humidity and temperature chamber  for testing. The capacitive responses of the sensor were measured as a function of RH with different ranges from 45% to 90% by a CV analyzer  at 40 kHz. The sensor exposure time to each RH environment was 5 min. After measurements, the sensors were stored in a dry environment. Cyclic bending was performed using a multi-modal bending tester  with a controlled radius and number of bending cycles. After bending, the sensing characteristics were measured with re-flat condition.For real-time monitoring, anisotropic conductive film bonder  were utilized to achieve electrical contact between the H-PTFE sensor and readout circuit. We already have mobile application systems used in previous studies. The humidity data of the H-PTFE sensor, transmitted via Bluetooth communication, was displayed in a mobile application.The schematic structure and a photograph of the H-PTFE flexible humidity sensor are shown in + ions have been reported to be very effective in changing the bond structure of PTFE [+ and OH− ions infiltrated the H-PTFE pore structure. Then, the Na+ ions break the strong carbon (C)–fluorine (F) bonds, and produce a small quantity of C–OH bonds [Although H-PTFE plays a significant role in water absorption, the water affinity of the sensor can be enhanced by treatment of NaOH on the H-PTFE humidity sensor. Na of PTFE ,17. The  of PTFE . When thOH bonds . These m2 and CF3 groups at 1201 cm−1, 1146 cm−1, 638 cm−1, and 502 cm−1 [−1 [−1 associated with OH [The FT-IR spectra provided information on the chemical functionalization of the PTFE surface upon treatment with NaOH. 502 cm−1 ,22. The cm−1 [−1 . Also, a with OH . This in4, compared to non-treated H-PTFE sensors under a same RH range. Not only was there the long-range linear behavior, but also the extremely low non-coincidence between absorption and desorption of the H-PTFE sensor with NaOH treatment was represented in In Abundant OH groups in the NaOH-treated H-PTFE film promote the physical and chemical absorption of water molecules, which provides a great advantage in detecting humidity in low-RH regions. Also, in high-RH regions, the water molecules absorbed on the H-PTFE surface make a secondary layer through physical adsorption by adjacent water molecules, which demonstrates a large increase in capacitance responses .To estimate the sensor performance in terms of reliability, we measured the capacitance responses of four H-PTFE sensors with regard to RH variation. There are several requirements to use our H-PTFE humidity sensor for real-time monitoring. High sensitivity, linearity, and reliability have already been mentioned above, and in terms of stability, we conducted additional experiments. First, to verify the sensing stability of our sensor under different temperatures, sensing responses were measured under a temperature range from 10 °C to 40 °C. The RH was fixed at 50% and 90%, respectively. As shown in n) of 100, 1000, and 3000 with a 10 mm bending radius. The back of the H-PTFE film was laminated with a 70 µm thick PET film to downshift the mechanical stress. As shown in Stable operation under mechanical stress also should be ensured for a flexible sensor. Herein, to confirm the performance variation of flexible H-PTFE humidity sensors under mechanical stress, we performed cyclic bending tests with different numbers of bending cycles  are designed, as shown in The flexible H-PTFE sensor was connected with the readout circuit by utilizing anisotropic conductive film bonder which is widely used for contact between electrodes. As shown in inset of In conclusion, we demonstrated the potential of a flexible sensor using H-PTFE as a dielectric sensitive film to perform reliable humidity monitoring. We showed that the sensor response was dependent on the RH. It was confirmed that NaOH treatment of the H-PTFE film further improved the sensitivity, detection dynamic range, and reliability of water uptake. The cycling bending test also proved the high mechanical flexibility of the humidity sensor. Finally, in order to validate the applicability for real-time monitoring, the flexible humidity sensor, integrated with an analog interface and wireless communication, was attached on the curved surface, and then was used to detect humidity changes. Our future efforts will be focused on improving the sensitivity and reproducibility of the sensor, and further extending this platform to humidity detection for industrial, environmental, and medical fields.


Other than the general role of graphene as a high-performance electron acceptor or transporter, the observed enhancement in photocatalytic activity over HTT/graphene can be ascribed to the improved interfacial charge migration from enhanced chemical bonding (Ti–C bonds) during the in-situ compositing process. The formation of Ti–C bonds is confirmed by XPS analysis and the resulting enhanced separation of photoinduced charge carriers is demonstrated by electrochemical impedance spectra and transient photocurrent response.Hydrogen titanate nanotube (HTT)/graphene nanocomposites are synthesized by hydrothermal reduction of graphene oxide (GO) and simultaneous preparation of nanotubular HTT via an alkaline hydrothermal process. By using this facile in-situ compositing strategy, HTT are densely supported upon the surface of graphene sheets with close interface contacts. The as-prepared HTT/graphene nanocomposites possess significantly enhanced visible light catalytic activity for the partial oxidation of benzylic alcohols. The amount of graphene has significant influence on catalytic activity and the optimal content of graphene is 1.0 wt %, giving a normalized rate constant  In the last several decades, the photocatalytic process in semiconductors has been attracting more and more attention as an advanced green technology for contaminant purification, energy production, and selective organic synthesis ,2,3. The2-derived nanosized materials appear to be a potential candidate, owing largely to their excellent performance, long term stability, low toxicity, and cost [2 nanostructures, such as TiO2 nanotubes, nanowires, and nanofibers [2(B) or anatase phase, exhibits higher catalytic performance for pollutant degradation than P25-TiO2 [2 or titanate remains problematic. Numerous strategies have been studied to tailor the photocatalytic process and promote catalytic performance. Particularly, fabrication of carbon-titanate heterojunction composites has been identified as one of the most feasible strategies to enhance the separation of electron-hole pairs [Among various photocatalysts, TiOand cost ,5. In thnofibers ,7,8. Thenofibers ,10. For P25-TiO2 ,12. Howele pairs ,14,15.2WO6 composites with strong covalent bonding between graphene and Bi2WO6 nanoparticles. The improved photocatalytic performance for H2 and O2 production were ascribed to the efficient electron migration and separation of photoinduced charge carriers through the chemically bonded interaction [2 nanoparticles. This chemical bonding effect plays a pivotal role in the interfacial electron migration, which makes TiO2/graphene composites possess an outstanding catalytic activity for the photo-oxidation of formaldehyde, compared to a mechanically mixed sample [Owing to the great surface area of graphene and its excellent electronic transport properties, many studies have been carried out on fabricating composite catalysts of graphene and semiconductor particles in an attempt to promote photocatalytic activity ,17. Undeeraction . Xie et d sample .3N4, HNb3O8 nanosheets, CdS, and TiO2-based composites [2 catalysts using visible light, although the photocatalysts themselves and the reactants can only absorb UV light [The selective oxidation of alcohol to carbonyl compounds is a significant chemical conversion process. Generally, the partial oxidations of alcohols are implemented with hazardous or toxic stoichiometric oxidants under high temperature and pressure conditions . Deteriomposites ,26,27,282 or TiO2 nanohybrids as photocatalysts [2O for hydrogen production [However, previously reported research on photocatalytic selective synthesis principally focused on reaction systems using TiOatalysts ,30,31. Toduction ,33, wherIn this paper, HT nanotube (HTT)/graphene nanohybrids with numerous heterogeneous interfaces are prepared via a facile hydrothermal method under basic conditions. Due to their one-dimensional structural characteristics, HT nanotubes can be uniformly coupled onto graphene to form close interfacial contacts. The presence of chemical Ti–C bonds between nanotubular HT and graphene are confirmed by XPS analysis. The HTT/graphene nanocomposites with chemically bonded interfaces exhibit exceptional photocatalytic reactivity toward the partial oxidation of benzylic alcohols under visible illumination. The influence of graphene content on the catalytic performance is investigated and a possible mechanism based on the experimental results is also proposed.4, H2SO4, H3PO4, H2O2 (30%), NaOH, P25 TiO2, and ethanol were obtained from Aladdin Industrial Inc. . Benzyl alcohol and its derivatives were purchased from J&K Scientific Ltd. . 5,5-Dimethyl-1-pyrroline-N-oxide was obtained from TCI Development Ltd. . All the other chemicals were of analytical reagent grade and used as received without further purification. Deionized water was obtained using a Millipore Milli-Q system and used throughout the experiments.Graphite was purchased from Nanjing XFNANO Materials Tech Co., Ltd. . KMnO2SO4/H3PO4  was added into a mixture of squama graphite and KMnO4 . Then, the obtained mixture was heated for 12 h at 323 K under magnetic stirring. After being cooled down to room temperature, the mixture was poured into an icy solution of 30% H2O2. The solid was recycled by filtration, washed by deionized water, and vacuum-dried at 298 K for 12 h. The obtained graphite oxide (GO) was dispersed in water (0.5 mg/mL) and subjected to sonication for 60 min to form an aqueous dispersion of exfoliated GO.To improve the hydrophilic and oxidation degree of graphite, a modified method was used to prepare graphite oxide . In brie2 was added to 65 mL of concentrated NaOH solution (10.0 M) and was stirred for 30 min to form a uniform suspension. Then, a specific amount of GO dispersion was added to the above-obtained suspension under magnetic stirring. The weight ratios of GO to P25 TiO2 were 0, 0.2, 0.4, 1.0, 2.0, and 4.0%, and the as-prepared samples are labeled as HTT/graphene-x%, where x refers to the mentioned weight ratios. After further stirring for 90 min, the mixture was transferred into a 100 mL stainless steel autoclave and heated at 160 °C for 12 h. The obtained precipitate was separated by centrifugation, washed by deionized water, and re-dispersed for several cycles until a pH value of nearly 8 was obtained. The precipitate was finally washed with absolute ethanol and dried at 90 °C for 10 h to obtain HTT/graphene-x% nanocomposites.In a typical synthesis process for HTT/graphene nanohybrids, 1.3 g of P25 TiO2 and NaOH solution. About 10 mg of graphene was added into 50 mL of deionized water and sonicated for 1 h. Then 1.0 g of as-made HTT was mixed into the graphene suspension under magnetic stirring. After being stirred for 2 h, the homogeneous suspension was treated by centrifugation. The precipitate was washed with deionized water and dried in a vacuum oven at 90 °C for 10 h. The as-obtained product is denoted as HTT/graphene-1.0%-mixed. For the preparation of the P25 TiO2/graphene-1.0% composite, 1.0 g of P25 TiO2 was added to 65 mL of deionized water and stirred for 30 min. 10 mL of GO dispersion (1.0 mg/mL) was added into P25 TiO2 suspension under magnetic stirring. After further stirring for 90 min, the mixture was transferred into a 100 mL Teflon-lined autoclave and heated at 160 °C for 12 h. The obtained precipitate was washed with deionized water and dried at 90 °C overnight. The as-synthesized sample is named as P25 TiO2/graphene-1.0%.For comparison, bare HTT and graphene samples were prepared using a similar process without GO or P25 TiO−1. X-ray photoelectron spectra were recorded using a Thermo Scientific ECALAB 250xi system with a monochromated Al Ka X-ray source. UV-visible diffuse reflectance spectra were collected on a UV-vis spectrophotometer  using BaSO4 as the reflectance standard. The specific surface area of as-synthesized samples were measured by N2 adsorption-desorption with a Micrometrics ASAP 2020 apparatus.X-ray diffraction measurements were conducted using a D8 Advance diffractometer (Bruker) with Cu Kα radiation (λ = 0.15418 nm). Raman spectra were recorded on a Labram HR 800 Raman spectrometer  using 532 nm excitation light at room temperature. The morphological features of HTT/graphene nanohybrids were observed by a transmission electron microscope  operating at 200 kV. FTIR spectra were acquired with a Nicolet 750 FTIR spectrometer in the range 400–4000 cm4 and nitrogen gas was continuously purged through the electrolyte solution. After being immersed in a benzyl alcohol solution for 1.5 h, the working electrode was irradiated using a 300 W Xe lamp with a 400 nm cut-off filter. Electrochemical impedance spectra (EIS) were measured using the above-mentioned three-electrode cell at 0.0 V with 0.1M Na2SO4 aqueous solution. Electron spin resonance (ESR) signals of the radicals trapped by DMPO were collected on a Bruker ER200-SRC spectrometer at ambient temperature.Photoelectrochemical experiments were performed in a standard three-electrode system. Platinum foil and Ag/AgCl were used as the counter and reference electrodes, respectively. The working electrode was prepared by the following method: 40 mg of powder sample was dispersed in 0.2 mL of polyethylene glycol solution and ultrasonicated for 45 min to obtain a uniform slurry. The resulting slurry was then spread on a fluorine doped tin oxide (FTO) conducting glass and was dried at 90 °C to get HTT/graphene/FTO electrodes. The photocurrent was recorded at a bias voltage of 0.6 V on an electrochemical workstation . The electrolyte was 0.1 M LiClO2 for 30 min. This suspension was stirred magnetically for another 60 min to reach the adsorption-desorption equilibrium of the reactant alcohols and catalysts. The mixture was then irradiated using a 300 W Xe lamp with 400 nm cut-off filter under ambient temperature. At certain time intervals, a 0.5 mL mixture was withdrawn and filtered using a Millipore filter (pore size 0.45 μm) to remove the catalyst particles. The concentration changes of reactants in the remaining filtrate were quantitatively analyzed on a gas chromatograph (Agilent 7890) equipped with a standard FID detector and a DM-5 amine capillary column. Oxidation products were identified by comparing the retention times with the standards and further confirmed with GC-MS.The partial conversion of benzyl alcohol was performed in a 20 mL round-bottom quartz glass flask. Benzyl alcohol (0.25 mmol) and the photocatalyst (50 mg) were dispersed into 5 mL of acetonitrile and the obtained mixture was bubbled with Otert-butyl alcohol, triethanolamine, and benzoquinone as the scavenger for the hydroxyl, photogenerated hole, and superoxide radicals, respectively) were performed via an analogous process of benzyl alcohol photo-oxidation, except that the radical scavenger (0.2 mmol) was included. The primary role of the active species were revealed by analyzing the changes of the benzyl alcohol conversion yield.In order to elucidate the photocatalytic mechanism, control experiments using different radical scavengers , suggesting an interfacial interaction between graphene and HTT in the nanocomposites.The presence of graphene in the HTT/graphene nanocomposites could be confirmed using FTIR spectra . Bare GO053 cm−1 . Compare−1 range for GO and HTT/graphene nanocomposites, as shown in 3 defects, and the latter gives information about the in-plane vibrations of sp2 bonded carbon [ID/IG) represents the relative concentration of defects in GO or graphene. Compared with bare GO, the calculated ID/IG of the HTT/graphene composites are lower, demonstrating a lower concentration of defects in graphene. The decreased ID/IG ratios in HTT/graphene nanohybrids imply the employed hydrothermal process facilitates the formation of more graphene without reducing the average size of sp2 domains. Furthermore, it is worth noting that a G band up-shift from 1588 to 1596 cm−1 is observed for HTT/graphene compared with GO and graphene, which gives evidence for chemical bonding of carbon materials [Raman spectroscopy is also widely employed to characterize the electronic structure of carbon products. Two bands are observed in the 850–2000 cmd carbon ,34. The aterials ,38. The The morphologies of HTT/graphene composites can be observed by TEM, as shown in 2 adsorption-desorption experiments were used to investigate the textual properties of the as-synthesized nanocomposites. The specific surface area, SBET was calculated according to the classical Brunauer–Emmett–Teller (BET) theory and the corresponding data are summarized in BET than bare HTT, which is due to the huge surface area of graphene [BET increases from 228.9 to 248.0 m2·g−1 when the content of graphene increases from 0.2% to 4.0% for as-synthesized HTT/graphene composites. There is no doubt that the enhanced SBET can provide more surface active sites and facilitate the adsorption of the reactants, thus promoting heterogeneous catalytic reactions.Ngraphene . Additio2-hybridized carbon of GO and the oxygen-containing carbonaceous bands (C–OH) [The interactions between HTT and graphene are further studied by XPS. The high-resolution C 1s XPS spectrum of bare GO is shown in s (C–OH) ,39. Thes1/2 and Ti 2p3/2 spin-orbital splitting photoelectrons of Ti4+. Two bands at binding energies of 463.3 and 457.7 eV usually correspond to Ti3+ [4+ and Ti3+ in HTT, two other weak peaks located at 465.3 and 459.4 eV are found and are likely due to the forming of Ti–C bonds in the HTT/graphene nanohybrids. This suggests that a chemical interaction between HTT and graphene is present in as-synthesized HTT/graphene composites and absent in the mixed samples.Forming Ti–C bonds is also investigated and identified by analyzing the Ti 2p XPS spectra of the HTT/graphene nanocomposites. As depicted in  to Ti3+ ,36. In F2/graphene -1.0%. As depicted in 2/graphene nanohybrids for contaminant degradation and hydrogen production [To investigate the photocatalytic performance of HTT/graphene nanohybrids, the selective oxidation of benzylic alcohols was chosen as a model reaction. No product of aldehyde was obtained without visible radiation or the photocatalyst, indicating that the selective oxidation of benzyl alcohol is conducted through the photocatalytic reaction. oduction ,20.2/graphene-1.0% and HTT/graphene-1.0%-mixed have also been tested and analyzed under the same experimental conditions. The sample of P25 TiO2/graphene-1.0% shows dramatically lower activity  than the HTT/graphene-1.0% composites, suggesting that more direct contact and the resulting strong interactions between HTT and graphene sheets are critical for the enhancement of photocatalytic activity because of improved electron/hole separation and migration. The physical mixed sample (HTT/graphene-1.0%-mixed) shows a significantly lower conversion yield than that of HTT/graphene-1.0% synthesized via a one-step hydrothermal process. This suggests that simple mechanical-mixing with graphene has a small effect on improving the photocatalytic activity of HTT, and is due to the absence of a chemical-bonding interface between HTT and graphene. This also indicates that the interaction state between HTT and graphene has crucial influence on photocatalytic performance of HTT/graphene nanohybrids.For comparison, the selective conversion of benzyl alcohol in P25 TiO0/Ct)  and the reaction time is displayed, indicating the oxidation is pseudo-first order. The pseudo-first-order rate constant (k) of the HTT/graphene photocatalysts can be obtained from the slope. The rate constant (k) of benzyl alcohol oxidation over the optimal photocatalyst, HTT/graphene-1.0%, is 0.411 h−1, which is 5.3 and 6.4 times higher than those of the P25 TiO2/graphene-1.0% and HTT/graphene-1.0% -mixed samples.Additionally, the reaction kinetics of benzyl alcohol oxidation were investigated and the corresponding results are shown in 3– and CH3O–) facilitate the formation of aldehyde products; for example, 97.6% of 4-methoxybenzyl alcohol can be converted in 4.5 h with 96% selectivity. Whereas, the electron-withdrawing substituents (such as F– and Cl–) retard the conversion of alcohols. This suggests that the existence of an electron-donating group at the p-position of benzyl alcohol benefits the selective conversion over an HTT/graphene photocatalyst.To investigate the general applicability of HTT/graphene composites, the oxidation of various benzylic alcohols over the optimal HTT/graphene-1.0% were examined and the corresponding results are displayed in The stability or recyclability of catalysts is another important practical issue. In order to study the stability and durability of HTT/graphene composites, cycle experiments are performed. After the catalytic reactions, HTT/graphene-1.0% photocatalysts are separated and recovered by washing, and are reused. As depicted in −1) after being adsorbed over HTT/graphene-1.0%. On the other hand, the characteristic peaks belonging to skeletal vibrations of the phenyl ring (at 1495 and 1451 cm−1) and the C–C stretching vibration (at 1207 cm−1) show no changes [2OH groups of the alcohol molecules interact with the unsaturated Ti sites of HTT, forming alcoholate species –CH2–O(H)–Ti.Surface adsorption generally plays a critical role toward photocatalysis-driven selective oxidation of alcohols. The surface adsorption of benzyl alcohol on HTT/graphene composites is first investigated using FTIR spectra A. In com changes ,28. Thes2–O(H)–Ti can produce visible absorption, which provides a prior condition for the selective conversion of benzylic alcohol to product aldehyde. This has been previously shown in research on photocatalytic reactions over TiO2 or Nb2O5 [2/graphene nanohybrids [The formation of surface complexes –CHor Nb2O5 ,41. Baseohybrids . AlthougThe band gap energy of the photocatalyst is an important factor affecting the catalytic performance, especially for a visible light photocatalytic system. The band gap energies of pure HTT, HTT/graphene-1.0%, and HTT/graphene-4.0% are estimated through a Tauc plot of the modified Kubelka–Munk function with linear extrapolations C. The caI-t curves of the above-mentioned three working electrodes in a benzyl alcohol containing electrolyte solution under visible light illumination. The photocurrent is primarily determined by the charge transfer from the adsorbed benzyl alcohols to the HTT conduction band and the subsequent graphene surface. The photocurrent density of the HTT/graphene-1.0% electrode is enhanced ~4.6 times that of pure HTT, indicating the separation efficiency of photoinduced charges can be improved by the interfacial electronic interactions between HTT and graphene. Moreover, the photocurrent density of the in-situ composited HTT/graphene-1.0% is enhanced ~2.3 times that of the mechanical-mixed hybrid (HTT/graphene-1.0%-mixed), which is primarily ascribed to the chemical interactions between HTT and the graphene sheets. Additionally, for the HTT/graphene-1.0% electrode, the photocurrent density in the presence of benzyl alcohol is predominantly higher than that in its absence. This result implies the generation of anodic photocurrent is closely related to the surface adsorption of benzyl alcohol upon the HTT/graphene-1.0% electrode. The photocurrent experiments offer direct evidence for electron migration from the adsorbed benzyl alcohol to the conduction band of HTT and subsequently to graphene surface under visible light.To investigate visible light induced charge transfer during the photo-oxidation of benzylic alcohols over HTT/graphene catalysts, the transient photocurrent responses were recorded over working electrodes made of pure HTT, HTT/graphene-1.0%-mixed and in-situ compositing HTT/graphene-1.0%. SBET normalized rate constants of benzyl alcohol oxidation. This suggests that visible light induced charge transfer plays a pivotal role in the photocatalytic conversion of benzylic alcohol. For graphene-based photocatalytic systems, the enhanced charge separation efficiency is dominated by the high spatial charge transportation properties of graphene [Based on the experimental data in graphene ,44. The graphene ,20,21,22graphene ,20,21,225, 2.2 × 105, and 1.0 × 105 ohm, determined by fitting with the equivalent circuit. This demonstrates that the introduction of graphene facilitates the charge transfer of HTT. Furthermore, the arc radius of the EIS Nyquist curve for HTT/graphene-1.0% is smaller than that of both the physically mixed (HTT/graphene-1.0%-mixed) and pure HTT samples. Generally, the arc radius of an EIS spectrum reflects the resistance of the interface layer at the surface of the electrodes [ectrodes ,45. The ectrodes ,45. Thestert-butyl alcohol (TBA) to the reaction solution [2 by sparging with N2 results in a low conversion of benzyl alcohol (ca. 15%), indicating that O2 plays a critical role in photocatalytic oxidation of benzyl alcohol. When triethanolamine  is put into the reaction system, the oxidation of benzyl alcohol is remarkably inhibited, implying that partial oxidation of benzyl alcohol is primarily driven by photo-holes. Additionally, the introduction of benzoquinone (BQ) results in an obvious decrease in the conversion of benzyl alcohol, suggesting that O2·ˉ is also involved during the photo-oxidation of benzyl alcohol. To confirm the formation of O2·ˉ, active radical species generated over HTT/graphene-1.0% are detected by ESR using DMPO as the spin-trapping agent. As depicted in 2·ˉ.The involved catalytic mechanism of alcohol photo-oxidation on HTT/graphene composites is further studied. Control experiments on radical trapping were carried out and the obtained results are illustrated in solution , the con2 to produce a superoxide anion radical. Meanwhile, the adsorbed benzylic alcohol transforms into an intermediate with a positive charge. Subsequently, the photogenerated hole drives the α-deprotonation of the intermediate and gives rise to a neutral carbon radical. Then the reaction between the substrate radical and superoxide species yields the product aldehyde. Compared to the HTT/graphene-mixed samples, the in-situ composited HTT/graphene catalysts possess significantly enhanced photocatalytic activity for the selective oxidation of benzylic alcohols under visible light illumination, as indicated in According to these results, a possible mechanism for the improved visible light catalytic activity over as-prepared HTT/graphene composites is proposed and depicted in −3 g/m2·h, which exceeds that of pure HTT by more than seven times. Further characterization results indicate that HTT are chemically bonded with graphene surfaces via Ti–C bonds, which is supported by XPS analysis. More importantly, the chemical-bonded nanocomposite exhibits a remarkable enhancement of photocatalytic activity, which is 5.2 times that of a mechanical-mixed sample. Based on the results of transient photocurrent and EIS, this enhancement can be ascribed to the interfacial charge transfer effect, which provides favorable spatial conditions for electrons migration from in-situ generated surface complexes to neighboring HTT and finally to graphene. This effect inhibits the recombination of electrons and holes, and thus yields superior photocatalytic performance. Our study on the efficient interfacial charge transfer via a chemically bonded interface provides new insights for guiding the design of novel photocatalytic reaction systems, particularly for solar-light driven selective organic synthesis.In summary, HTT/graphene nanohybrids with superior photocatalytic activity were fabricated through a facile hydrothermal process. Nanotubular HTT are densely supported upon the surface of graphene with close interfacial contacts. Introducing graphene can markedly improve the catalytic performance for the selective conversion of benzylic alcohols under visible illumination and the contents of graphene have significant effects on the catalytic activity of HTT. The optimal content of graphene is 1.0 wt % and the corresponding normalized rate constant k of benzyl alcohol oxidation is 1.71 × 10


Sarcoidosis is a granulomatous lung disorder of unknown cause. The majority of individuals with sarcoidosis spontaneously achieve full remission (uncomplicated sarcoidosis), however, ~20% of sarcoidosis-affected individuals experience progressive lung disease or cardiac and nervous system involvement (complicated sarcoidosis). We investigated peripheral blood mononuclear cell (PBMC) microRNA and protein-coding gene expression data from healthy controls and patients with uncomplicated or complicated sarcoidosis. We identified 46 microRNAs and 1,559 genes that were differentially expressed across a continuum of sarcoidosis severity . A total of 19 microRNA-mRNA regulatory pairs were identified within these deregulated microRNAs and mRNAs, which consisted of 17 unique protein-coding genes yielding a 17-gene signature. Pathway analysis of the 17-gene signature revealed Jak-STAT signaling pathway as the most significantly represented pathway. A severity score was assigned to each patient based on the expression of the 17-gene signature and a significant increasing trend in the severity score was observed from healthy control, to uncomplicated sarcoidosis, and finally to complicated sarcoidosis. In addition, this microRNA-regulated gene signature differentiates sarcoidosis patients from healthy controls in independent validation cohorts. Our study suggests that PBMC gene expression is useful in diagnosis of sarcoidosis. Lung involvement is commonly manifested as bilateral hilar lymphadenopathy and pulmonary infiltration with more severe cases developing pulmonary fibrosis. Cardiac and neurologic involvement are also associated with significant morbidity and death4. This broad spectrum of clinical manifestations makes diagnosis challenging and prolonged.Sarcoidosis remains a systemic inflammatory disease of unknown etiology with an unpredictable course that affects all races and ethnicities that is characterized by the presence of non-caseating epithelioid granulomas in one or multiple organs. The disorder is extremely heterogeneous with more than 50% of sarcoidosis patients experience remission within 3 years after diagnosis, and over 66% of patients experiencing remission within 10 years6. Acute phase reactants like serum amyloid (SAA) levels are significantly higher in active disease similarly to ACE7, but likewise suffers from low specificity and sensitivity. HLA-DR allele and cytokines such as tumor necrosis factors  are overexpressed in sarcoidosis as well and correlated with fibrosis development8. No single biomarker has proven to exhibit significant sensitivity and specificity to be recommended as a monitoring and prognostic tool for standard clinical use.Clearly validated biomarkers that can accurately sub-phenotype patients with sarcoidosis are of enormous utility as they may identify subjects at increased risk of complicated sarcoidosis and allow for the delivery of targeted therapies to prevent progressive multi-organ deterioration. Unfortunately, blood, bronchoalveolar lavage fluid, exhaled breath concentrate, and cerebrospinal fluid have all been assessed as sarcoidosis biomarkers by multiple methodologies, including enzyme-linked immunosorbent assay and proteomic analysis, but with limited success. For example, angiotensin converting enzyme (ACE) is the most commonly studied biomarker but is non-specific and does not accurately correlate with severity11, particularly relevant in assessment of personal risk for developing complicated sarcoidosis10. For example, Koth et al. analyzed the transcriptomic gene expression data from whole blood of sarcoidosis patients and accordingly built a classifier using the gene expression data, which distinguished sarcoidosis patients from healthy controls in an external validation cohort with a fairly good accuracy9. Recently, we investigated genome-wide gene expression in peripheral blood mononuclear cell (PBMC) in sarcoidosis patients and identified a 20-gene signature, which distinguishes uncomplicated sarcoidosis from complicated sarcoidosis10. This gene signature also exhibited a substantial predictive power when classifying sarcoidosis patients from healthy controls in two external cohorts.As a consequence, we and others have proposed the integration of blood gene expression profiling as an opportunity to explore potential useful molecular signatures in sarcoidosisIn this study, we proposed to incorporate microRNA (miRNA) expression information with protein-coding gene expression data to identify sarcoidosis biomarkers. Firstly, we identified a list of differentially expressed miRNAs in PBMCs from patients with sarcoidosis. Secondly, we searched for a list of target protein-coding genes for the deregulated miRNAs and based on these target genes, developed a novel miRNA-regulated peripheral blood gene signature that accurately differentiates sarcoidosis patients from healthy controls and complicated sarcoidosis patients from uncomplicated ones. Pathway analysis of the gene signature revealed Jak-STAT signaling pathway as the most significantly represented pathway. A severity score, based on the expression of the gene signature, exhibited a significantly increasing trend from healthy control, to uncomplicated sarcoidosis, and finally to complicated sarcoidosis. These studies suggest that PBMC gene expression is useful in diagnosis of sarcoidosis, and more importantly, in the identification of patients with complicated sarcoidosis.P < 0.05) that were differentially expressed with severity . In total, we identified 46 miRNAs (adjusted 12 accession: GSE37912). Spearman’s rank correlation test was conducted between gene expression and sarcoidosis severity. In total, 1,559 genes showed significant correlation (adjusted P < 0.0005), among which 340 genes showed positive correlation between gene expression and severity while the expression of 1,219 genes was negatively correlated with severity  to select the top miRNA-mRNA binding pairs14. We intersected these predicted binding targets against the differentially expressed protein-coding genes revealing a total of 425 miRNA-mRNA pairs. Among these miRNA-mRNA pairs, we only retained the pairs that demonstrated a significant negative correlation (adjusted P < 0.005) between miRNA and mRNA expression. This step yielded 19 miRNA-mRNA pairs consisting of eight unique miRNAs and 17 unique protein-coding genes  was assigned to each patient based on the expression of the 8-miRNA signature, which is a linear combination of the miRNA expression values weighted by direction of differential expression (See Methods for details). Higher SmiRNA implies more severe sarcoidosis. As expected, a significant positive correlation (Spearman’s rank correlation test: ρ = 0.651 and P = 4.4 × 10−9) was identified between SmiRNA and sarcoidosis severity in our discovery cohort . The 8-miRNA signature based severity score of sarcoidosis patients is significantly higher than that of controls in the Germany cohort (t-test: P = 3.4 × 10−6)  is 1.000 in this cohort −6) Fig. . The areort Fig. , which sort Fig. .Figure 3Sgene) to each patient based on the expression of the 17-gene signature, which is a linear combination of the protein-coding gene expression values weighted by direction of differential expression (see Methods for details). Patients with more severe sarcoidosis are expected to have a higher Sgene. Not surprisingly, we found a significant positive correlation (Spearman’s rank correlation test: ρ = 0.615 and P = 5.6 × 10−9) between Sgene and sarcoidosis severity in our discovery cohort . The other dataset (GEO accession: GSE18781)18 is from Oregon Health Sciences University and includes 25 healthy controls and 12 sarcoidosis patients (Oregon cohort). The 17-gene signature-based severity score of sarcoidosis patients is significantly higher than that of controls in both the validation cohorts (t-test: P = 1.5 × 10−8 for the UCSF cohort and P = 3.8 × 10−5 for the Oregon cohort) rt) Fig. . The AUCely Fig. . Principely Fig. .Figure 4P = 1.9 × 10−2 and 2.09 × 10−5) .To understand the discriminative power of the 17-gene signature in distinguishing sarcoidosis from other lung diseases, we collected two more blood transcriptomic datasets (GEO accession: GSE42826 and GSE4257), the first consisted of 52 healthy controls, 25 sarcoidosis patients, 11 tuberculosis (TB) patients, six pneumonia patients, and eight lung cancer patients. TB, pneumonia patients, lung cancer were considered as non-sarcoidosis lung disorders. The second dataset comprised of 123 healthy controls, 87 and 47 cases with COPD and sarcoidosis respectively. Principal component analysis on the expression of the 17-gene signature in this dataset indicates that the first principal component significantly differentiates the sarcoidosis patients from the non-sarcoidosis lung disorders in both datasets   Fig. .AUC in both validation cohorts. Figure P = 0.019).We next addressed whether the classification power of the 17-gene signature is superior to the other genes that are related to sarcoidosis. To answer this question, we conducted a second resampling test. We limited the resampling pool to the genes that were differentially expressed with sarcoidosis severity  that potentially relate to sarcoidosis severity, including miR-23a, miR-23b, miR-30c, miR-185, and miR-223, now recognized to be related to pulmonary hypertension18. Jak-STAT signaling pathway is an intracellular cascade initiated in response to cytokine signaling. Several genes in Jak-STAT pathways have already been associated with sarcoidosis, such as IL1531, IL23R32, and STAT118. According to the current knowledge of the molecular mechanism leading to sarcoidosis, genes involved in T-cell receptor selection, T-cell activation and apoptosis, and cytokine regulation are also highly associated with the pathogenesis of sarcoidosis33. In our 17-gene signature, CBLB and IL6ST are known to be involved in T-cell receptor signaling and cytokine-cytokine receptor interaction, respectively, according to the definition in KEGG database. However, we failed to identify a single gene within our 17-gene signature that overlapped with the previously published sarcoidosis blood gene signatures by Koth et al.9 and Zhou et al.10, respectively.We also explored the utility of a protein-coding gene expression signature in sarcoidosis. We identified the 17-gene signature, in which the genes were potentially regulated by the miRNAs within the 8-miRNA signature. In agreement with prior reported studies, the 17-gene signature was enriched in Jak-STAT signaling pathwayet al. suggests that resampling test should be used to evaluate the predictive power of a given gene signature instead of focusing on nominal P-value, because most the published signatures are not significantly better than the randomized gene signatures of identical size20. Using resampling tests, we found that the classification power of the 17-gene signature is significantly better than that of the random gene sets selected from human genome.A published bioinformatical study by Venet et al.9 and Zhou et al.10, the 17-gene signature was developed based on miRNA expression information and predefined miRNA-gene interactions. Statistically-derived gene signatures by whole genome screening are often highly accurate in the patient data sets from which they were identified, yet most of them have not been validated as useful clinical tools. Using resampling test, we demonstrate that the miRNA-regulated 17-gene signature performs even better than the random gene sets selected from the pool of sarcoidosis related genes, which suggests that incorporation miRNA expression information into gene signature identification may significantly decrease false positive rate when developing gene signatures for complex human diseases.In contrast to the published sarcoidosis gene signatures derived from whole genome screening by Koth et al. recently published overexpression of miRNas involved in angiogenesis, miRNA -27b, miR-192 and miR-221 in BALF cells from patients with acute sarcoidosis, none of these were significantly overexpressed in PBMCs34. Crouser et al. also profiled DE-miRNA in lung and lymph tissue and observed no overlap in miRNA expression in PBMC relative to diseased lung tissue; however TGF Fβ/WNT was a commonly regulated pathway30. Jazwa et al., suggested miRNA-34 regulates SIRT1 and the expression of IFN- γ in sarcoidosis35.Despite multiple efforts to identify concordant DE-miRNA in sarcoidosis, it is recognized that patterns of miRNA expression differ between BAL cells, lung tissue, lymph nodes and PBMCs suggesting organ specific regulation. In our initial 8-miRNa signature we identified miR-23a, miR-23b, miR-30c, miR-185, and miR-223 related to sarcoidosis severity. Kiszalkiewicz In summary, we derived a molecular signature consisting of 17 protein-coding genes, which are potentially regulated by deregulated miRNA in sarcoidosis. This signature can be independently used as potential novel molecular markers for differentiating patients with sarcoidosis, especially for distinguishing the patients with risk of complicated sarcoidosis. Although gene expression variation in PBMCs may not necessarily reflect the dynamics of the tissue microenvironment in sarcoidosis patients, PBMC gene expression information is useful in diagnosis of sarcoidosis, and more importantly, in the identification of patients with complicated sarcoidosis.36, neurologic sarcoidosis (e.g. evidence of hyperdense MRI lesions)37, or severe pulmonary sarcoidosis  . The healthy controls were collected in a matching procedure for both age and gender of the patients. As for the sarcoidosis patients, we didn’t find significant difference in age (t-test: P > 0.05) and gender (χ2-test: P > 0.05) between uncomplicated and complicated cases. Patient characteristics and treatment information are summarized in Supplementary Table The study was approved by the University of Arizona Institutional Review Board with written informed consent obtained from all subjects, and was performed in accordance with the principles in the Declaration of Helsinki. We defined complicated sarcoidosis as cardiac sarcoidosis (e.g. ventricular arrhythmias)normexp with offset value 10 based on a convolution model39 and normalized using the global Lowess regression algorithm. Only the miRNAs being present in at least two third of total samples were further analyzed. The miRNA expression data of the validation cohort, the Germany cohort, were obtained from the GEO database (GEO accession: GSE34608), which were based on Agilent-019118 Human miRNA Microarray 2.0 G4470B.For the discovery cohort, we profiled the PBMC miRNA expression level for 35 healthy controls, 17 patients with uncomplicated sarcoidosis, and 13 patients with complicated sarcoidosis, using Exiqon miRCURY LNA Array v11.0 . Total RNA was isolated from PBMCs according to manufacturer’s protocol. Array hybridization was performed by Exiqon with the quantified signals background corrected using 10, which were based on Affymetrix Human Exon 1.0ST Array. Briefly, gene expression data were summarized using robust multi-array average (RMA) algorithm40 embedded in the Affymetrix Power Tools v.1.12.0. Adjustment for possible batch effect was conducted by COMBAT41. We consider a transcript cluster to be reliably expressed in these samples if the Affymetrix implemented DABG (detection above ground)42P-value was less than 0.01 in at least two third of total samples. The gene expression data of the UCSF (GEO accession: GSE19314)9 and Oregon cohorts (GEO accession: GSE18781)18 were downloaded from the GEO database, which were based on Affymetrix Human Genome U133 Plus 2.0 Array.The protein-coding gene expression data of the discovery cohort are available from the GEO database (GEO accession: GSE37912)SmiRNA) is a linear combination of expression values of the miRNAs within the 8-miRNA signature. The formula is shown below:NmiRNA is the number of miRNAs in the 8-miRNA signature; i  is a linear combination of expression values of the genes within the 17-gene signature45. The formula is shown below:Ngene is the number of protein-coding genes in the 17-gene signature; i (as shown in Table i; i across all samples, respectively; and “sgn” denotes the sign function.8-miRNA and 17-gene based severity scores were calculated for each human subject, respectively. 8-miRNA based severity score (entclass1pt{minimaSupplementary Information


Research suggests that consumers often mishandle food in the home based on survey and observation studies. There is a need for a standardized tool for researchers to objectively evaluate the prevalence and identify the nature of food safety risks in the domestic environment. An audit tool was developed to measure compliance with recommended sanitation, refrigeration and food storage conditions in the domestic kitchen. The tool was piloted by four researchers who independently completed the inspection in 22 homes. Audit tool questions were evaluated for reliability using the κ statistic. Questions that were not sufficiently reliable (κ < 0.5) or did not provide direct evidence of risk were revised or eliminated from the final tool. Piloting the audit tool found good reliability among 18 questions, 6 questions were revised and 28 eliminated, resulting in a final 24 question tool. The audit tool was able to identify potential food safety risks, including evidence of pest infestation (27%), incorrect refrigeration temperature (73%), and lack of hot water . The audit tool developed here provides an objective measure for researchers to observe and record the most prevalent food safety risks in consumer’s kitchens and potentially compare risks among consumers of different demographics. Despite numerous interventions and regulations meant to control contamination of food products, foodborne illness continues to be a major public health problem in the United States, with an estimated 9.4 million cases, 56,000 hospitalizations and 1400 deaths each year . The majStaphylococcus aureus [Escherichia coli [Campylobacter jejuni [Salmonella spp. [Listeria monocytogenes [The presence of microbial contamination in the domestic environment has been well documented. Enteric bacteria, normally eliminated by proper cooking or by adequate sanitation, have been isolated from almost every surface in the kitchen ,13,14,15s aureus ,15,16,17hia coli ,13,16,17r jejuni , Salmonella spp. ,19, and ytogenes ,20,21. TEscherichia coli, Shigella, and S. aureus. Contamination on the hands can significantly increase the spread of microorganisms around the kitchen, for pathogens picked up from handling raw meat as well as enteric pathogens from the food preparer [Cross contamination is the transfer of harmful microorganisms from raw food to utensils, surfaces, or other foods. During meal preparation up to 71% of consumers were observed touching surfaces in the kitchen directly after handling raw meat ,23. Conspreparer ,28. Almopreparer ,29, but preparer ,23.Listeria monocytogenes and Staphylococcus aureus.Temperature abuse may occur when a food is heated or cooled improperly. Many consumers report using visual or tactile methods to know when meat is done cooking, such as checking the color of the meat or feeling the meat for firmness and texture ,30. ThesAlthough most authors agree that consumers frequently mishandle food at home there is a lack of consistency between results from study to study. Self-reported data, the most common method to evaluate consumer food handling behavior, is inconsistent and reported behavior does not always represent actual behavior . When coVisual inspection to document conditions related to food safety is the traditional method used to evaluate retail and foodservice settings, including restaurants, hospitals, and schools ,38. In oThis type of visual inspection may also be useful to study consumer households. Unlike other methods, the use of an audit tool provides a standardized checklist to record conditions that are actually present at the time of inspection. The instructions and questions on the audit tool must be evaluated for reliability to ensure they are clear and objective. A reliable instrument will produce the same results after repeated use, such as use by multiple people to evaluate a given set of conditions. This type of reliability, called inter-rater reliability, measures the extent to which a group of raters agree in their responses to a question . This stSome studies have utilized this approach to evaluate specific conditions in the domestic environment, such as refrigerator cleanliness and organization ,41, presAn audit tool was developed to measure compliance with recommended sanitation, refrigeration, and food storage conditions in the domestic kitchen. The instrument is formatted as a checklist, with multiple-choice questions to be used by the researcher to record visual observations from the environment. This method is commonly used in the food industry to inspect restaurants and food service establishments, and several pre-existing audit tools served as a model for the one created in this study ,45. A liIn order to be included in the audit tool each question had to be related to at least one target behavior, directly observable, and able to be measured or determined objectively. All conditions that are either directly associated with target behaviors or necessary to control the target behavior were further evaluated. From this list only conditions that could be directly observed by the auditor, with no input from the participant, were considered. The last criterion for inclusion was measurability and objectivity of the questions. In order for an instrument to be reliable each question must be able to be measured objectively, with no chance of different interpretations between different observers using the tool. While many conditions could be easily measured in an objective way, some were inherently subjective but considered especially relevant to food safety. For these criteria a set of observation guidelines were created to accompany the audit tool. These guidelines provided a list of standards that allowed the auditor to observe a subjective quality (such as “cleanliness”) in an objective way.It should be noted that the audit tool was developed and modified based on the assumption that the consumer would practice appropriate hygiene and food handling practices. That is, if soap and towels are available they will be used for proper handwashing. Similarly, if cleaning supplies are available they will be utilized and if cutting boards are available they will be used appropriately to avoid cross contamination. Actual observations of how consumers utilized available supplies were not conducted. Similarly therefore, it was assumed that a lack of supplies for proper hygiene and food handling would make it likely that these practices were not being carried out, and therefore increase risk.i.e., Cross Contamination Hazards, Time/Temperature Abuse, etc.), and were reorganized into groups based on location in the kitchen. This format allowed auditors to complete the inspection in an efficient and systematic manner. The final instrument contained five sections, each referring to a specific area of the kitchen and bathroom: General Kitchen, Kitchen Sink, Counters/Cabinets, Refrigerator/Freezer, and Bathroom Hygiene. The initial audit tool developed for the pilot study consisted of 52 questions.Three experts with backgrounds in food safety and domestic hygiene reviewed the draft audit tool for accuracy, usability, relevance to the domestic environment and overall completeness. The questions on the audit tool were originally categorized by food safety topic (p < 0.05) based on a lowest acceptable κ of 0.6 with a goal κ of 0.8 [The audit tool was pilot tested in domestic kitchens to determine inter-rater reliability of the questions as well as to further refine the instrument. For this study the lowest level of kappa (κ) acceptable to consider a question sufficiently reliable was initially set at 0.6—the high end of moderately significant κ values . It was κ of 0.8 .A convenience sample was recruited from Drexel University in Philadelphia, PA, USA, via department-wide e-mail advertisements and through word of mouth. The email included information about the commitment required for the study (a single home visit lasting approximately 20 min), the eligibility criteria , and the compensation ($20.00 in cash). Volunteers were asked to contact the researcher if they were interested in participating in the study. Appointments were given on a first come, first serve basis in order to reach the goal of 22 participants. A total of 38 people volunteered to participate in the study. From those 38 volunteers, three responded too late (after completion of the pilot study), seven provided contact information but could not be reached, four lived too far away and two canceled their appointments and were unable to reschedule. Volunteers were screened for eligibility via telephone questionnaire prior to scheduling appointments.Four researchers conducted inspections in 22 homes in and around the city of Philadelphia, PA, USA during May and June 2012. This study was approved by the Drexel University Institutional Review Board (IRB) and all participants were asked to sign informed consent forms before participating in the study. Prior to the onset of data collection a comprehensive training session was held to familiarize the auditors with the instrument. During this time the auditors reviewed the guidelines for recording observations, clarified the meanings of important terms used throughout the audit tool, and discussed how to handle unexpected scenarios. Informal training sessions were done periodically throughout the duration of the pilot study to remind the auditors to follow certain guidelines or to address new issues.At the participant’s home, each of the four auditors conducted an independent observation of the domestic environment using the audit tool. During this time the auditors did not discuss their observations with each other and could only consult their list of guidelines to determine how to evaluate conditions. The audit tool contained five sections and a total of 52 questions. The majority of the questions were multiple choice with only two answer choices (YES or NO), with a few open-ended sub-questions. Each section was followed by a blank space for the auditor to record any additional comments or relevant observations.The General Kitchen section contained 10 questions about the overall state of the kitchen, such as whether pets were observed on or near surfaces where food is prepared, evidence of pest infestation, maintenance of trash receptacles, and the availability and storage of cleaning materials. Six questions were included in the Kitchen Sink section to record if soap was present (and what type), evaluate the overall cleanliness of the sink, drain, and sponge/dishcloths. Kitchen water temperature was measured by running water into a container with an immersed thermometer , −20 to 110 °C; Ertco; Lafayette, NJ, USA) placed in the sink. Water was run for five minutes or until reaching 43 °C, whichever came first. The Counters/Cabinets section contained 11 questions about the overall condition and cleanliness of appliances, kitchenware, counters and utensils. This section also asks the observer to record if the participant owns a meat thermometer.The fourth section, Refrigerator/Freezer, was the longest section with 22 questions. Questions from this section recorded the condition and cleanliness of the refrigerator and freezer (interior and exterior), food storage methods , adherence to expiration and use-by dates, and the presence of foods commonly associated with foodborne pathogens . The temperature of the refrigerator was also measured using a pen-style infrared thermometer  and recorded in this section. This was done by holding the thermometer approximately 2 inches away from a food container as close to the middle of the refrigerator as possible, immediately after opening the refrigerator door. The last section, Bathroom Hygiene, contained two questions about the presence of soap and hand towels near the bathroom sink only if a bathroom was present on the same level of the home in which the kitchen was located.The auditors were encouraged to record additional comments or to elaborate on their answers as often as possible to provide the most complete picture of the conditions in the home. Upon completion of the inspection each participant was compensated $20 and provided with basic food safety information.Audit tool data from home inspections was numerically coded and entered into an Excel spreadsheet. κ statistic was calculated and used to evaluate inter-rater reliability for each question on the audit tool . Observan = 11) were male, and the rest female. Participant age ranged from 21 to 75 with a mean age of 31. The purpose of this pilot study was to evaluate the reliability, functionality and appropriateness of the audit tool, rather than record individual characteristics of the participants. For this reason a convenience sample was used and minimal demographic information was obtained.All 22 participants were located in or around the city of Philadelphia, PA, USA. Half of the participants (n = 22). Missing data was encountered for 13 questions when raters unintentionally left a question blank. Any question with a missing response was omitted from the analysis and κ was calculated for the remaining number of homes (n < 22).A summary of the κ values for 24 questions which were eventually included in some format in the final audit tool is shown . In mostκ values for questions from the audit tool varied from −0.031 to 1.0, with the minimum acceptable level of agreement pre-set at κ = 0.6. Of the initial 52 questions included in the audit tool, three questions had a κ of less than zero, indicating the level of agreement between raters was less than what was expected by chance. Eight questions had slight to fair agreement (κ = 0–0.2) and twelve questions had moderate levels of agreement (κ = 0.41–0.60). Seven questions had substantial levels of agreement (κ = 0.61–0.80) and the remaining 16 questions had almost perfect agreement (κ ≥ 0.81). Many of the questions on the audit tool with moderate levels of agreement (0.41–0.60) related to the condition and cleanliness of countertops, sinks, cutting boards and refrigerators . These cMany conditions related to unsafe food handling behaviors were observed using the audit tool. These results represent only a small number of homes (22), however indicate that the audit tool is capable of detecting a range of unsafe food handling conditions in the domestic environment. Observations related to cleaning and sanitation revealed several potential risks, such as a lack of cleaning materials other than dish soap in 5% of homes audited . Food coSeveral conditions were observed that may increase risk of cross contamination in the domestic environment . Evidencn = 6) were below the recommended temperature of 5.0 °C and 9% (n = 2) had temperatures greater than 10 °C.Conditions related to time and temperature abuse of food were identified in a majority of the homes audited . Meat thThe goal of this pilot test was to create a user friendly, reliable instrument that was appropriate to audit the domestic kitchen to be used in a larger study and potentially by other researchers. Based on these results two types of modifications were required to create the final version of the audit tool—eliminating questions that were particularly cumbersome or not essential for the goals of the project, and eliminating questions with low reliability. First, audit tool questions that were related to overall sanitation but considered least likely to contribute to the presence of foodborne pathogens in the home were eliminated. Items that were considered least likely to be directly associated with the presence of pathogens included evidence of tobacco use in the kitchen, maintenance of trash cans, and cleanliness of kitchen appliances. Questions that were particularly difficult and cumbersome to observe were also eliminated. The draft audit tool contained 22 questions in the Refrigerator/Freezer section, many of which required the rater to spend a significant amount of time moving food items to look through the refrigerator. This task becomes extremely difficult with more than one rater and if the refrigerator is very full, so many items from this section were omitted in the final version.Only half of the questions from the audit tool met the standard for the minimum acceptable level of reliability determined prior to the onset of the study (κ ≥ 0.6). Ten questions with low κ scores were considered non-essential or cumbersome and eliminated right away. The remaining 13 questions were considered particularly relevant to the goals of the study and necessary to include in the final instrument. Six of these 13 questions had a κ score between 0.5 and 0.6 and were included “as is” in the final audit tool because κ of above 0.5 is still considered a moderate level of agreement . The sevIn order to improve the reliability of questions that scored low in the pilot study the audit tool guidelines and instructions were also modified. The original guidelines were several pages in length, making them difficult to refer to during inspections. Changes to the guidelines decreased the length to a single page and helped clarify subjective questions. For example, the modified guidelines list exactly what criteria are necessary to consider a sponge or dishcloth dirty. Another problem that occurred during the pilot study was the tendency of raters to overlook certain items, such as not looking in a specific drawer in the refrigerator for meat products. The audit tool instructions have been modified to clearly state if the rater should look in specific locations to answer the question .This research has resulted in the development and validation of a user friendly, objective audit tool available with instructions for use see . It is i