We report a study of the response of InAs nanowire field-effect transistor sensor devices to various gases and alcoholic vapors. It is concluded that the change in conductance of the device in response to chemical vapors is a combined result of both the charge transfer and modified electron mobility effects. In particular, we found that surface adsorption of most chemical molecules can reduce electron density in nanowires from approximately 10(4) to approximately 10(3)/microm and enhance the electron mobility greatly (from tens to a few hundred of cm(2)/(V s)) at the same time. These effects are attributed to the interactions between adsorbed molecules and the electron accumulation layer and rich surface states on the InAs nanowire surface.

The martensitic transition, magnetocaloric effect (MCE) and shape memory effect (MSE) of ferromagnetic Heusler alloys Ni50Mn50−xSbx (x = 12, 13 and 14) have been investigated. A large positive magnetic entropy change ΔSM was observed in the vicinity of the martensitic transition. The maximum value of ΔSM is 9.1 J kg−1 K−1 in Ni50Mn37Sb13 at 287 K for a magnetic field change of 5 T. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic parent phase. A magnetic-field-induced shape recovery strain of about 15 ppm at room temperature and at a relatively low magnetic field (1.2 T) was observed to accompany the reverse martensitic transformation. The large field-induced MCE and MSE in the NiMnSb system make it a promising material for room-temperature application.

Control of ferromagnetism is of critical importance for a variety of proposed spintronic and topological quantum technologies. Inducing long-range ferromagnetic order in ultrathin 2D crystals will provide more functional possibility to combine their unique electronic, optical and mechanical properties to develop new multifunctional coupled applications. Recently discovered intrinsic 2D ferromagnetic crystals such as Cr2Ge2Te6, CrI3 and Fe3GeTe2 are intrinsically ferromagnetic only below room temperature, mostly far below room temperature (Curie temperature, ~20–207 K). Here we develop a scalable method to prepare freestanding non-van der Waals ultrathin 2D crystals down to mono- and few unit cells (UC) and report unexpected strong, intrinsic, ambient-air-robust, room-temperature ferromagnetism with TC up to ~367 K in freestanding non-van der Waals 2D CrTe crystals. Freestanding 2D CrTe crystals show comparable or better ferromagnetic properties to widely-used Fe, Co, Ni and BaFe12O19, promising as new platforms for room-temperature intrinsically-ferromagnetic 2D crystals and integrated 2D devices.

A new type of HOF-based gas sensor with high selectivity, ultra-fast response and a lower limit of detection to NO2 has been developed for the first time.

The magnetocaloric effect and refrigeration capacity ͑RC͒ of Gd 55 Co 20 Al 25 and Gd 55 Ni 25 Al 20 bulk metallic glasses ͑BMGs͒ have been investigated. Large magnetic entropy changes ⌬S M of 11.2 and 10.8 J kg −1 K −1 and large RC values of 846 and 920 J kg −1 are obtained for Gd 55 Co 20 Al 25 and Gd 55 Ni 25 Al 20 , respectively, at a field change of 7 T. The RC value ͑640 J kg −1 at 5 T or 920 J kg −1 at 7 T͒ of Gd 55 Ni 25 Al 20 BMG is larger than that reported for all magnetocaloric materials, including crystalline and amorphous materials measured under the same conditions. The large RC value is due to the broad ⌬S M peak ͑more than 100 K͒, which is caused by the disordered structure of an amorphous material. The large ⌬S M and RC values make these Gd-based ternary BMGs attractive candidates for magnetic refrigeration applications.

The magnetic phase transitions and the magnetocaloric effect in the Ising antiferromagnet DySb have been studied. A field-induced sign change of the magnetocaloric effect has been observed which is related to a first-order field-induced metamagnetic transition from the antiferromagnetic to the ferromagnetic states at/below the Néel temperature TN, while the negative field-induced entropy change is found to be associated with the first-order magnetic transition from the paramagnetic to the ferromagnetic states above TN. The large magnetic-entropy change (−20.6J∕kgK at 11K for a field change of 7T), together with small hysteresis, suggests that DySb could be a potential material for magnetic refrigeration in the low-temperature range.

A large reversible magnetocaloric effect has been observed in Tb3Co compound. Under a magnetic field change of 5T, the maximum value of magnetic entropy change ΔSM is −18Jkg−1K−1 at 84K and the relative cooling power is 738Jkg−1 with no hysteresis loss. In particular, the large reversible ΔSMmax, −8.5Jkg−1K−1, is achieved for a low magnetic field change of 2T. The magnetic anisotropy and the texture of the material greatly affect ΔSM. The large reversible magnetocaloric effect (both the large ΔSM and the high relative cooling power) indicates that Tb3Co could be a promising candidate for magnetic refrigeration.

In the development of proton conductors, it is very important to increase the density of proton carriers to adjust proton conduction pathways. In this work, two novel isomeric hydrogen-bonded organic frameworks, [(HDATA) 2 (H 2 BPYBPA)-(H 2 O) 2 ] (UPC-H1 and UPC-H2), together with their dehydrated counterpart, [(HDATA) 2 (H 2 BPYBPA)] (UPC-H3), were successfully assembled from acidic H 4 BPYBPA and alkaline DATA. Single crystal X-ray diffraction analysis clearly reveals the threedimensional lattice water molecules-involved hydrogen-bonded networks for UPC-H1 and UPC-H2 and no lattice water moleculeinvolved hydrogen-bonded network for UPC-H3. Detailed structural analysis with the aid of water adsorption tests discloses their easy single-crystal-to-single-crystal (SCSC) transformation and good self-adaptability to water molecules through hydrogen-bonded reorganization under the help of electrostatic interactions. Owing to the lack of restriction from the lattice water molecules in UPC-H3, the adsorbed water molecules more easily reorganize hydrogen bonds to form smooth proton conduction pathways, endowing it good proton conductivity over a wide temperature range from 30 to 80 °C at 95% relative humidity (RH), with the highest value of 9.0 × 10 −2 S cm −1 at 80 °C and 99% RH, despite the lack of channels and permanent voids in its crystal structure.