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The impact of environmental regulation on enterprise innovation is closely related to the competitiveness of the enterprise and sustainable development of the regional economy, but existing research does not provide a consistent view. This paper summarizes the impacts of environmental regulation on enterprise innovation from the perspectives of technological innovation, product innovation, system innovation and ecological innovation. We find that the impacts of environmental regulation on enterprise innovation behaviour are complex, and that the impacts can be reflected together by the four aspects above and even by their interaction. Moreover, the impacts are not limited to the creation of new technologies, products, and systems but also include their adoption and application. In particular, whether the Porter hypothesis is true and which versions of the Porter hypothesis environmental regulation causes in enterprise innovation depend on enterprise characteristics, means of environmental regulation, and enterprises' strategic behaviours in an enterprise ecosystem. Finally, we propose five potential research directions: quantifying the degree of enterprise innovation caused by environmental regulation, the impacts of environmental regulation on sustainable economic development from an enterprise ecosystem perspective, the impacts of enterprise innovation on environmental regulation, the role of enterprise initiative in the relationship between environmental regulation and enterprise innovation, and social security issues and the integration of eliminated enterprises resulting from environmental regulation.

Recently, inorganic perovskite CsPbI2 Br has gained much attention for photovoltaic applications owing to its excellent thermal stability. However, low device performance and high open-voltage loss, which are the result of its intrinsic trap states, are hindering its progress. Herein, planar CsPbI2 Br solar cells with enhanced performance and stability were demonstrated by incorporating rubidium (Rb) cations. The Rb-doped CsPbI2 Br film exhibited excellent crystallinity, pinhole-free surface morphology, and enhanced optical absorbance. By using low-cost carbon electrodes to replace the organic hole-transportation layer and metal electrode, an excellent efficiency of 12 % was achieved with a stabilized efficiency of over 11 % owing to the suppressed trap states and recombination in the CsPbI2 Br film. Additionally, the annealing temperature for the Rb-doped CsPbI2 Br film could be as low as 150 °C with a comparable high efficiency over 11 %, which is one of the best efficiencies reported for hole-transporting-layer-free all-inorganic perovskite solar cells. These results could provide new opportunities for high-performance and stable inorganic CsPbI2 Br solar cells by employing A-site cation substitution.

Effects of 0.5 wt% CuO addition on the sintering, structural and electrical properties of perovskite layer structured (PLS) Sr2Nb2O7 ceramics prepared by solid-state reaction method are investigated. The addition of CuO is beneficial to the liquid phase bridge formation at sintering process, leading to lower sintering temperature of 1180°C and larger bulk density up to 98%. Meanwhile, CuO modified Sr2Nb2O7 ceramics show a remarkable d33 of (1.1 ± 0.1) pC/N while still with a very high Tc of (1340 ± 2)°C. Raman spectra indicate that the improvement of piezoelectricity could be attributed to the rotation and/or distortion of oxygen octahedron caused by possible Cu2+ substitution at the A-sites of Sr2Nb2O7.

Lattice dynamics and phase transitions of Aurivillius ferroelectric Bi3Ti1−xWxNbO9+δ (BTWN100x, 0 ≤ x ≤ 15%) ceramics have been investigated by temperature-dependent Raman spectra (80–800 K) and far-infrared (FIR) reflectance spectra (6–300 K). The frequency, intensity, and line width of phonon modes as well as complex dielectric functions of BTWN100x ceramics have been extracted by fitting Raman and FIR reflectance spectra with the multi-Lorentzian oscillator model. It was found that the dielectric constants at a certain frequency region become lower with increasing W compositions at room temperature due to the compressive stress on W–O bands. Moreover, the temperature-dependent behavior of optical phonon modes in BTWN100x ceramics indicates that there are two intermediate phases during the phase transition from paraelectric I4/mmm to ferroelectric A21am phase on cooling. The phase diagram of BTWN100x ceramics as a function of W composition has been improved.

A combination of polarized Raman technique, infrared reflectance spectra, and first-principles density-functional theoretical calculations were used to investigate structure transformation and lattice vibrations of Na0.5Bi0.5TiO3, Na0.5Bi0.5TiO3–5%BaTiO3, and Na0.5Bi0.5TiO3–8%K0.5Bi0.5TiO3 single crystals. It was found that Na0.5Bi0.5TiO3 is of a two-phase mixture with rhombohedral and monoclinic structures at room temperature. Correspondingly, three Raman-active phonon modes located at 395, 790, and 868 cm−1, which were previously assumed as A1 modes of rhombohedral phase have been reassigned as A′′, A′, and A′ modes of monoclinic phase in the present work. In particular, a strong low-frequency A′′ mode at 49 cm−1 was found and its temperature dependence was revealed. Two deviations from linearity for the abrupt frequency variation in the A′′ mode and Ti–O bond have been detected at temperatures of ferroelectric to antiferroelectric phase transition TF–AF and dielectric maximum temperature Tmax. The appearance of Na–O vibrations at 150 cm−1 was found below Tmax, indicating the existence of nanosized Na+TiO3 clusters. The observed Raman and infrared active modes belonging to distinct irreducible representations are in good agreement with group-theory predictions, which suggests 9A1+9E and 36A′′+24A′ modes for the rhombohedral and monoclinic phases of Na0.5Bi0.5TiO3, respectively.

Low-symmetry 2D materials with unique anisotropic optical and optoelectronic characteristics have attracted a lot of interest in fundamental research and manufacturing of novel optoelectronic devices. Exploring new and low-symmetry narrow-bandgap 2D materials will be rewarding for the development of nanoelectronics and nano-optoelectronics. Herein, sulfide niobium (NbS3 ), a novel transition metal trichalcogenide semiconductor with low-symmetry structure, is introduced into a narrowband 2D material with strong anisotropic physical properties both experimentally and theoretically. The indirect bandgap of NbS3 with highly anisotropic band structures slowly decreases from 0.42 eV (monolayer) to 0.26 eV (bulk). Moreover, NbS3 Schottky photodetectors have excellent photoelectric performance, which enables fast photoresponse (11.6 µs), low specific noise current (4.6 × 10-25 A2 Hz-1 ), photoelectrical dichroic ratio (1.84) and high-quality reflective polarization imaging (637 nm and 830 nm). A room-temperature specific detectivity exceeding 107 Jones can be obtained at the wavelength of 3 µm. These excellent unique characteristics will make low-symmetry narrow-bandgap 2D materials become highly competitive candidates for future anisotropic optical investigations and mid-infrared optoelectronic applications.

2D layers of metal dichalcogenides are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. 2D SnS2 nanosheets with a bandgap of ≈2.6 eV have been attracting intensive attention as one potential candidate for modern electrocatalysis, electronic, and/or optoelectronic fields. However, the controllable growth of large-size and high-quality SnS2 atomic layers still remains a challenge. Herein, a salt-assisted chemical vapor deposition method is provided to synthesize atomic-layer SnS2 with a large crystal size up to 410 µm and good uniformity. Particularly, the as-fabricated SnS2 nanosheet-based field-effect transistors (FETs) show high mobility (2.58 cm2 V-1 s-1 ) and high on/off ratio (≈108 ), which is superior to other reported SnS2 -based FETs. Additionally, the effects of temperature on the electrical properties are systematically investigated. It is shown that the scattering mechanism transforms from charged impurities scattering to electron-phonon scattering with the temperature. Moreover, SnS2 can serve as an ideal material for energy storage and catalyst support. The high performance together with controllable growth of SnS2 endow it with great potential for future applications in electrocatalysis, electronics, and optoelectronics.

Anomalous low temperature behaviors in cuprous oxide (Cu2O) film grown on quartz substrate have been investigated by temperature-dependent Raman and transmittance spectra. The longitudinal optical components of two Γ15- phonon modes become sharper and more intense at a low temperature. It can be found that the highest-order electronic transition located at 6.4 eV exhibits a minimum transmittance near 200 K. Correspondingly, the variations from phonon intensity ratios reveal obvious anomalies with the decreasing temperature, indicating the existence of strong electron–phonon coupling mediated by Frohlich interaction in the Cu2O films below the temperature of 200 K. Copyright © 2012 John Wiley & Sons, Ltd.

Cu2ZnSnS4 (CZTS) absorbers were grown by sulfurization of the Sn-rich precursors that were cosputtered from a CuSn target (2 in.) and a ZnS target (2 in.). The excess Sn in the precursor could limit the decomposition of CZTS during the long sulfurization process at 510 °C. The sulfurized CZTS film cosputtered with CuSn 45 W and ZnS 70 W exhibits the intended bandgap of 1.53 eV, main Raman mode at 335.5 cm−1 and a slightly Sn-rich composition. As the sputtering power of the CuSn target was increased from 45 to 60 W, the corresponding films consisted of a CZTS phase and several Sn-rich phases (SnS/Sn2S3/Cu4Sn7S16). Conversely, when this sputtering power was reduced to 35 W, the resultant film consisted of a CZTS phase and a ZnS secondary phase. Besides, Raman scattering shows that the increased sputtering power of the CuSn target is related with the redshift and the increased FWHMs of primary Raman modes for the resultant films. X-ray diffraction data show the (112)-oriented growth and lattice expansion for the obtained CZTS films.

The temperature dependence of Raman spectra for SrBi2−xNdxNb2O9 ceramics (x from 0 to 0.2) has been studied in a wide temperature range from 80 to 873 K. It is found that the peak position of the A1g[Nb] phonon mode at 207 cm–1, which is directly associated with the distortion of NbO6 octahedron, decreases with increasing Nd composition, while the A1g[O] phonon mode at 835 cm–1 increases. Moreover, both the peak position and intensity of the A1g[Nb] phonon mode reveal strong anomalies around the ferroelectric to paraelectric phase transition temperature. It indicates that the phase transition temperature decreases from about 710 to 550 K with increasing Nd composition, which is due to the fact that the introduction of Nd ions in the Bi2O2 layers reduces the distortion extent of NbO6 octahedron. Copyright © 2011 John Wiley & Sons, Ltd.

A new approach for extraction of Nb from Nb-bearing complex iron ore, found in North-West China, is proposed. Selective reduction of the complex iron oxides by CO-CO 2 gas mixture was conducted, and the reduced metallic Fe was magnetically separated from the Nb-bearing gangue residue. The Nb-rich product was leached with HCI to remove P. A highly concentrated Nb-bearing product with Nb/Fe = 6, Nb/P = 12 might be possible to make commercial grade of 60-65 % Nb ferroniobium.

Environmentally friendly synthesis of carbon nanoprticles (C-NPs) from folic acid (FA) is realized with the assistance of microplasma. TEM shows that the synthesized FA C-NPs are amorphous and of diameter around 47 nm. The produced FA C-NPs exhibit an excitation independent emission around 445 nm with the fluorescence quantum yield 13% at excitation wavelength of 370 nm. X-ray photoelectron spectroscopy (XPS) shows the FA C-NPs are composed of carbon (64.15%), nitrogen (6.04%), and oxygen (29.81%). Raman spectroscopy shows that the intensity ratio between the sp3 and sp2 hybridizations of Carbon is 0.35. UV-Vis absorption, Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance (NMR) spectra provide a deep insight into the fluorescence of FA C-NPs. With plasma processing of FA, carbon atoms are involved in sp2 hybridization and amine (NH2), NH and COOH groups are converted into ROOCNHCOOR group. As a consequence, the electron donating ability of aromatic ring is enhanced, which plays an important role in the fluorescence of FA C-NPs. Finally, the promising application of FA C-NPs in bioimaging is also demonstrated by fluorescence labeling of MCF-7 cancer cells.

Materials that respond rapidly and reversibly to external stimuli currently stand among the top choices as actuators for real-world applications. Here, a series of programmable actuators fabricated as single- or bilayer elements is described that can reversibly respond to minute concentrations of acetone vapors. By using templates, microchannel structures are replicated onto the surface of two highly elastic polymers, polyvinylidene fluoride (PVDF) and polyvinyl alcohol, to induce chiral coiling upon exposure to acetone vapors. The vapomechanical coiling is reversible and can be conducted repeatedly over 100 times without apparent fatigue. If they are immersed in liquid acetone, the actuators are saturated with the solvent and temporarily lose their motility but regain their shape and activity within seconds after the solvent evaporates. The desorption of acetone from the PVDF layer is four times faster than its adsorption, and the actuator composed of a single PVDF layer maintains its ability to move over an acetone-soaked filter paper even after several days. The controllable and reproducible sensing capability of this smart material can be utilized for actuating dynamic elements in soft robotics.