24 research outputs found
Strongly coupled hybrid nanostructures for selective hydrogen detection-understanding the role of noble metals in reducing cross-sensitivity
Noble metal-semiconductor hybrid nanostructures can offer outperformance to gas sensors in terms of sensitivity and selectivity. In this work, a catalytically activated (CA) hydrogen sensor is realized based on strongly coupled Pt/Pd-WO3 hybrid nanostructures constructed by a galvanic replacement participated solvothermal procedure. The room-temperature operation and high selectivity distinguish this sensor from the traditional ones. It is capable of detecting dozens of parts per million (ppm) hydrogen in the presence of thousands of ppm methane gas. An insight into the role of noble metals in reducing cross-sensitivity is provided by comparing the sensing properties of this sensor with a traditional thermally activated (TA) one made from the same pristine WO3. Based on both experimental and density functional theory (DFT) calculation results, the cross-sensitivity of the TA sensor is found to have a strong dependence on the highest occupied molecular orbital (HOMO) level of the hydrocarbon molecules. The high selectivity of the CA sensor comes from the reduced impact of gas frontier orbitals on the charge transfer process by the nano-scaled metal-semiconductor (MS) interface. The methodology demonstrated in this work indicates that rational design of MS hybrid nanostructures can be a promising strategy for highly selective gas sensing applications. ? 2014 the Partner Organisations
Photometric stereo with near point lighting:A solution by mesh deformation
We tackle the problem of photometric stereo under near point lighting in this paper. Different from the conven-tional formulation of photometric stereo that assumes par-allel lighting, photometric stereo under the near point light-ing condition is a nonlinear problem as the local surface normals are coupled with its distance to the camera as well as the light sources. To solve this non-linear problem of PS with near point lighting, a local/global mesh deformation approach is developed in our work to determine the posi-tion and the orientation of a facet simultaneously, where each facet is corresponding to a pixel in the image captured by the camera. Unlike nonlinear optimization schemes, the mesh deformation in our approach is decoupled into an it-eration of interlaced steps of local projection and global blending. Experimental results verify that our method can generate accurate estimation of surface shape under near point lighting in a few iterations. Besides, this approach is robust to errors on the positions of light sources and is easy to be implemented. 1
Surface-from-gradients:An approach based on discrete geometry processing
In this paper, we propose an efficient method to recon-struct surface-from-gradients (SfG). Our method is formu-lated under the framework of discrete geometry processing. Unlike the existing SfG approaches, we transfer the contin-uous reconstruction problem into a discrete space and effi-ciently solve the problem via a sequence of least-square op-timization steps. Our discrete formulation brings three ad-vantages: 1) the reconstruction preserves sharp-features, 2) sparse/incomplete set of gradients can be well handled, and 3) domains of computation can have irregular boundaries. Our formulation is direct and easy to implement, and the comparisons with state-of-the-arts show the effectiveness of our method. 1
Just Noticeable Visual Redundancy Forecasting: A Deep Multimodal-Driven Approach
Just noticeable difference (JND) refers to the maximum visual change that human eyes cannot perceive, and it has a wide range of applications in multimedia systems. However, most existing JND approaches only focus on a single modality, and rarely consider the complementary effects of multimodal information. In this article, we investigate the JND modeling from an end-to-end homologous multimodal perspective, namely hmJND-Net. Specifically, we explore three important visually sensitive modalities, including saliency, depth, and segmentation. To better utilize homologous multimodal information, we establish an effective fusion method via summation enhancement and subtractive offset, and align homologous multimodal features based on a self-attention driven encoder-decoder paradigm. Extensive experimental results on eight different benchmark datasets validate the superiority of our hmJND-Net over eight representative methods
Low-Temperature H2S Detection with Hierarchical Cr-Doped WO3 Microspheres
Hierarchical Cr-doped WO3 microspheres have been successfully synthesized for efficient sensing of H2S gas at low temperatures. The hierarchical structures provide an effective gas diffusion path via well-aligned micro-, meso-, and macroporous architectures, resulting in significant enhancement in sensing response to H2S. The temperature and gas concentration dependence on the sensing properties elucidate that Cr dopants remarkably improve the response and lower the sensor’ operating temperature down to 80 °C. Under 0.1 vol % H2S, the response of Cr-doped WO3 sensor is 6 times larger than pristine WO3 sensor at 80 °C. We suggest the increasing number of oxygen vacancies created by Cr dopants to be the underlying reason for enhancement of charge carrier density and accelerated reactions with H2S.MOE (Min. of Education, S’pore
Surrounding Sensitive Electronic Properties of Bi2Te3 Nanoplates-Potential Sensing Applications of Topological Insulators
National Basic Research Program of China [2007CB310500]; National Science Foundation of China [61376073]Significant efforts have been paid to exploring the fundamental properties of topological insulators (TIs) in recent years. However, the investigation of TIs as functional materials for practical device applications is still quite limited. In this work, electronic sensors based on Bi2Te3 nanoplates were fabricated and the sensing performance was investigated. On exposure to different surrounding environments, significant changes in the conducting properties were observed by direct electrical measurements. These results suggest that nanostructured TIs hold great potential for sensing applications
Temperature-Dependent Abnormal and Tunable p‑n Response of Tungsten Oxide–Tin Oxide Based Gas Sensors
We observed the sensing response
of temperature-dependent abnormal
p–n transitions in WO<sub>3</sub>–SnO<sub>2</sub> hybrid
hollow sphere based gas sensors for the first time. The sensors presented
a normal n-type response to ethanol at elevated temperatures but abnormal
p-type responses in a wide range of operation temperatures (room temperature
to about 95 °C). By measuring various reducing gases and applying
complex impedance plotting techniques, we demonstrated the abnormal
p-type sensing behavior to be a pseudo-response resulting from the
reaction between target gas and adsorbed water on the material surface.
The temperature-controlled n–p switch is ascribed to the competition
of intrinsic and extrinsic sensing behaviors, which resulted from
the reaction of target gas with adsorbed oxygen ions and protons from
adsorbed water, respectively. The former can modulate the intrinsic
conductivity of the sensor by changing the electron concentration
of the sensing materials, while the latter can regulate the conduction
of the water layer, which contributes to the total conductivity as
an external part. The hollow and hybrid nanostructures facilitated
the observation of extrinsic sensing behaviors due to its large-area
active sites and abundant oxygen vacancies, which could enhance the
adsorption of water. This work might give new insight into gas sensing
mechanisms and opens up a promising way to develop practical temperature
and humidity controllable gas sensors with little power consumption
based on the extrinsic properties
Low-Temperature H<sub>2</sub>S Detection with Hierarchical Cr-Doped WO<sub>3</sub> Microspheres
Hierarchical Cr-doped WO<sub>3</sub> microspheres have been successfully
synthesized for efficient sensing of H<sub>2</sub>S gas at low temperatures.
The hierarchical structures provide an effective gas diffusion path
via well-aligned micro-, meso-, and macroporous architectures, resulting
in significant enhancement in sensing response to H<sub>2</sub>S.
The temperature and gas concentration dependence on the sensing properties
elucidate that Cr dopants remarkably improve the response and lower
the sensor’ operating temperature down to 80 °C. Under
0.1 vol % H<sub>2</sub>S, the response of Cr-doped WO<sub>3</sub> sensor
is 6 times larger than pristine WO<sub>3</sub> sensor at 80 °C.
We suggest the increasing number of oxygen vacancies created by Cr
dopants to be the underlying reason for enhancement of charge carrier
density and accelerated reactions with H<sub>2</sub>S
Stapled RGD Peptide Enables Glioma-Targeted Drug Delivery by Overcoming Multiple Barriers
Malignant glioma,
the most frequent and aggressive central nervous system (CNS) tumor,
severely threatens human health. One reason for its poor prognosis
and short survival is the presence of the blood–brain barrier
(BBB) and blood–brain tumor barrier (BBTB), which restrict
the penetration of therapeutics into the brain at different stages
of glioma. Herein, inspired by the peptide stapling technique, we
designed a cyclic RGD ligand via an all-hydrocarbon staple (stapled
RGD, sRGD) to facilitate BBB penetration while retaining the capacity
of BBTB penetration and targeting ability to glioma cells. As expected,
sRGD-modified micelles were able to penetrate the in vitro BBB model
while retaining the glioma targeted capability. The results of the
in vivo imaging studies further revealed that this nanocarrier could
not only efficiently transverse the intact BBB of normal mice, but
also could specifically target glioma cells of intracranial glioma-bearing
nude mice. Furthermore, Paclitaxel-loaded sRGD-modified micelles exhibited
improved antiglioma efficacy in vitro and significantly prolonged
survival time of glioma-bearing nude mice. Overall, this sRGD peptide
showed potency for glioma-targeted drug delivery by overcoming multiple
barriers