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A method for achieving the accurate measurement of the antiferroelectric-ferroelectric (AFE-FE) phase switching time based on the electrically induced light scattering effect was designed. The AFE-FE switching times of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics decreased with the increase of the applied electric fields, and the logarithm of the switching time was approximately proportional to the electric field reciprocal. The random orientation of the polycrystalline structures with dispersion-distributed mixed phases of the PLZT transparent ceramics was the intrinsic mechanism affecting the corresponding switching times in the applied electric field. The smaller electrode size samples switched faster than the larger samples in the same electric field. The size effect of the switching times occurred due to the higher dielectric constant of the ceramics and the parameters of the test circuit, and the larger capacitance of the samples resulted in a longer rising time of the applied electric field, which in turn slowed down the phase switching and prolonged the switching time.

Luminescent inorganic perovskite nanocrystals (PeNCs) are promising in various optical applications, particularly in advanced lighting and displays. The instability of PeNCs and PeNC composites from different aspects hinder their practical applications. Many previous methods indicate that an intact and facile wrapping strategy could effectively address this challenge. In this work, we introduce an in situ ligand polymerization (ILP) method for the fabrication of PeNC composites. By introducing (3-aminopropyl)triethoxysilane (APTES) as the initial ligand of the PeNCs directly and polymethylhydrosiloxane (PMHS) as the monomer to form the polymerized matrix, a polymerized and hydrophobic SiO2 matrix structure is formed, which intrinsically protects the PeNCs against moisture-induced deterioration. The stability test indicates that the ILP composite powders demonstrate an improved stability against various solvent conditions and light exposure compared to the conventional PeNCs–SiO2 composite. More importantly, the ILP composite exhibits an excellent compatibility with the acrylate solvent which is widely used for light-solidification in light converting film fabrication. The ILP composite film demonstrates an ultrastable operational performance in our standard test outperforming the conventional PeNCs–SiO2 composite configuration. Thus, the ILP composite demonstrates great potential for use in advanced lighting and displays.

Low-dimensional lead-free metal halides, which feature strong quantum confinement effects, have recently attracted great attention due to their excellent optical properties and favorable stability under ambient conditions. Although controllable synthetic strategies, structural characterization and linear optical properties of lead-free metal halides have been widely reported, relevant studies on their nonlinear optical properties are still lacking, which hinders their applications in nonlinear photonic devices. Herein, two types of millimeter-level high-crystallinity cesium copper halide single crystals (SCs), i.e., Cs3Cu2I5 and CsCu2I3, with high photoluminescence (PL) quantum yields, are synthesized using an antisolvent vapor-assisted crystallization method. Their phonon energies are comparatively studied by using Raman spectroscopy and temperature-dependent PL spectroscopy. More importantly, comparison studies of the multiphoton absorption (MPA) properties of Cs3Cu2I5 and CsCu2I3 SCs are performed for the first time. Strong multiphoton excited PL emissions with large anisotropy factors are observed in these two types of SCs. Through the measurement of nonlinear transmittance, it is found that CsCu2I3 SCs exhibit much larger MPA coefficients compared with Cs3Cu2I5 SCs, which is attributed to the larger density of states in the former. This work broadens the applications of cesium copper halides in nonlinear optoelectronics and light polarization related devices.

Hybrid organic-inorganic metal halides have emerged as highly promising materials for a wide range of applications in optoelectronics. Incorporating chiral organic molecules into metal halides enables the extension of their unique optical and electronic properties to chiral optics. By using chiral (R)- or (S)-methylbenzylamine (R-/S-MBA) as the organic component, we synthesized chiral hybrid copper halides, (R-/S-MBA)2 CuCl4 , and investigated their optical activity. Thin films of this material showed a record anisotropic g-factor as high as approximately 0.06. We discuss the origin of the giant optical activity observed in (R-/S-MBA)2 CuCl4 by theoretical modeling based on density functional theory (DFT) and demonstrate highly efficient second harmonic generation (SHG) in these samples. Our study provides insight into the design of chiral materials by structural engineering, creating a new platform for chiral and nonlinear photonic device applications of the chiral hybrid copper halides.

In recent years, it has witnessed a rapid development of the fluorescent carbon dots (CDs) due to their unique optical properties and wide range of applications. However, difficulties in synthesizing long wavelength-emitting CDs have been the major drawback of CDs, which limited their applications in fields such as bioimaging and carbon-based white light-emitting diodes. Herein, on the basis of surface electron state engineering, we prepared surface metal-ion-functionalized CDs by treating solvothermally synthesized CDs with alkali metal aqueous solutions (LiOH, NaOH or KOH). Especially, we focused the CDs treated with LiOH solution (Li-CDs) because these CDs’ absolute photoluminescence quantum yield is as high as 34% in dilute ethanol solution under 550 nm excitation compared with those treated with NaOH or KOH solutions. The electron transport effect of alkali metal ions was confirmed. Moreover, the obtained Li-CDs show high optical pH sensitivity within pH values 1–4.5 and were applied to pH sensing. This work not only proposes a feasible and controllable method to construct long wavelength-emitting CDs, but also shows the application potentiality such as pH sensing devices.

Crystalline calcium aluminates are a critical setting agent in cement. To date, few have explored the microscopic and dynamic mechanism of the transitions from molten aluminate liquids, through the supercooled state to glassy and crystalline phases, during cement clinker production. Herein, the first in situ measurements of viscosity and density are reported across all the principal molten phases, relevant to their eventual crystalline structures. Bulk atomistic computer simulations confirm that thermophysical properties scale with the evolution of network substructures interpenetrating melts on the nanoscale. It is demonstrated that the glass transition temperature (T g) follows the eutectic profile of the liquidus temperature (T m), coinciding with the melting zone in cement production. The viscosity has been uniquely charted over 14 decades for each calcium‐aluminate phase, projecting and justifying the different temperature zones used in cement manufacture. The fragile–strong phase transitions are revealed across all supercooled phases coinciding with heterogeneous nucleation close to 1.2T g, where sintering and quenching occur in industrial‐scale cement processing., The evolution mechanism of different calcium‐aluminate phases during fast heating to about 3200 K and subsequent cooling is revealed by measuring their associated thermophysical properties (e.g., viscosity and density) using the self‐developed aerodynamic levitation technique and by bulk‐scale computationally modeling these properties and the atomistic structural changes. The fragile‐to‐strong phase transitions are discovered across all supercooled calcium‐aluminate liquids.

As a new kind family of lead-free Na0.5Bi0.5TiO3 (NBT) ceramics, bismuth layer-structured ferroelectrics (BLSFs), Na0.5BixTi3.98Mg0.02Oy (x = 4.48, 4.50, 4.52) were synthesized by a conventional mixed oxide route. Studies have found that the dielectric properties of Na0.5Bi4.5Ti4O15 can be optimized through changing the Bi content of the ceramics or Mg-doping on Ti-site under different sintering temperatures. X-ray diffraction analysis indicated that the new material was in a single BLSFs phase. The dielectric constant of Mg-doped Na0.5Bi4.5Ti3.98Mg0.02Oy was improved and dielectric loss of Na0.5Bi4.5Ti3.98Mg0.02Oy changed slowly under 500 °C with the increased sintering temperature. We found that the dielectric properties of the sample sintered at 1120 °C with the highest permittivity of 1122.5 and the lowest dielectric loss of 0.01 were relatively better than those of the other samples. SEM can be better to explain the results of the dielectric spectrum at different sintering temperatures through grain size mechanics. Z* plots showed that Na0.5Bi4.5Ti3.98Mg0.02Oy ceramics are a kind of dielectrics. Thus, Na0.5BixTi3.98Mg0.02Oy (x = 4.48, 4.50, 4.52) can be used as high-temperature capacitors and phase shifter with high dielectric constant, low dielectric loss and wide operating temperature range.

Perovskite nanocrystals (PeNCs) are attractive in high-color gamut display technology as light converters which can achieve saturated green and red lights, respectively. However, PeNCs are intrinsically fragile against ambient conditions, such as moisture and oxygen and it is hard to maintain their performance in long-term operation. In this work, a new hierarchical encapsulation method is proposed, integrated with surface modification by halide ions protection, nano-scaled encapsulation by in situ capping SiO2 and embedding into poly (methyl methacrylate) (PMMA) matrix composites, to achieve a stable perovskite light converting composite sheet for LED remote-type encapsulation. The storage stability, as well as the operational stability of perovskite composites, were confirmed by the spectra evolution from encapsulated LEDs with normalized blue emission intensity. The 2D maps of spectra and aging measurement indicate that the silica encapsulation can well protect the PeNCs in the PMMA matrix from the ambient circumstance during a long-term storage process. Additionally, the hierarchical encapsulation for PeNCs/silica/PMMA showed better operational stability than the direct encapsulation of PeNCs/PMMA, and the correspondent Commission Internationale de L'Eclairage color coordinates tracking also indicated more stable color properties, which demonstrates the great potential in photoluminescent display applications.

Chiral ligand conjugated transition metal oxide nanoparticles (NPs) are a promising platform for chiral recognition, biochemical sensing, and chiroptics. Herein, we present chirality-based strategy for effective sensing of mercury ions via ligand-induced chirality derived from metal-to-ligand charge transfer (MLCT) effects. The ligand competition effect between molybdenum and heavy metal ions such as mercury is designated to be essential for MLCT chirality. With this know-how, mercury ions, which have a larger stability constant ( K f ) than molybdenum, can be selectively identified and quantified with a limit of detection (LOD) of 0.08 and 0.12 nmol/L for D-cysteine and L-cysteine (Cys) capped MoO 2 NPs. Such chiral chemical sensing nanosystems would be an ideal prototype for biochemical sensing with a significant impact on the field of biosensing, biological systems, and water research-based nanotoxicology.

A method based on the Stokes vectors was developed for the measurement of electro-optical (EO) coefficients, and the detailed test principle, experimental apparatus and data processing were described. The practicability of this method was illustrated by the determination of the EO coefficient of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics, and the measurement results indicated that the standard deviation values of the EO coefficients obtained by the Stokes vector method was almost half of that of the values measured using the Senarmont compensator method. The apparatus used for the Stokes vector method consists of only a few optical elements and was easy to adjust and calibrate, thereby enabling scientific, accurate, and efficient EO coefficient measurements for the development of EO materials and devices.

Using the vanadium oxyacetylacetone (VO(AcAc)2) as the precursor and white powdery tungstic acid as the doping W source, we fabricated the W-doped porous VO2 films by spin-coating method followed by annealing under the N2 atmosphere at 550 °C for half an hour. Compared to the pure VO2 film, the 5 at.% W-doped film exhibits a simultaneous enhancement of the near-IR switching efficiency at 2000 nm from 47.5 to 55.0 % and the maximum value of visible transmittance at 30 °C from 39.5 to 46.7 % as well as the one at 90 °C from 44.7 to 58.1 %, which further confirmed the practicability of introducing pores into the VO2 film as a strategy to enhance the thermochromic properties. In addition, a possible connection is presented about the relationship of metal–insulator transition process and the evolution of the phase compositions and morphology. A possible connection between the morphology and the thermochromic performance for the W-doped VO2 films was presented.

Porous thermochromic pure and tungsten (W)-doped vanadium dioxide (VO2) films have been prepared on silica substrates by spin coating via a sol–gel process and annealing in ammonia (NH3) atmosphere. NH3 with weak reducing capacity can prevent V4+ from further oxidization and contribute to the formation of porous structure. These films exhibit enhanced visible transparency and switching property at near-infrared wavelengths across the metal–insulator transition (MIT). The transmittance change in the VO2 film annealed at 2.0 × 103Pa is as high as 52.9 % at λ = 2000 nm, and its solar modulation efficiency reaches up to 9.4 %. W-doping shifts the MIT temperature of the VO2 films from 55 to 28 °C, while the films remain the excellent modulating ability in near-infrared region, and the decreasing efficiency of V0.99W0.01O2 film can achieve to 20 K/at.%, which will greatly favor the practical application of VO2-based smart windows. Transmittance spectra for pure VO2 film in the range of 250–2500 nm and the recorded transmittance–temperature hysteresis loop in the range of 20–90 °C of the W-doping VO2 films after annealing at 500 °C for 30 min (middle inset).

CdSe quantum dots (QDs) were introduced as an interlayer in the poly(3-hexylthiophene)(P3HT)/TiO 2 nanorod arrays (NRAs) hybrid solar cells. The presence of CdSe QDs was found to provide enhanced light absorption, assisting charge separation at the P3HT/TiO 2 interface, and leading to a lower recombination rate of the electrons due to the stepwise structure of band edge in P3HT/CdSe/TiO 2 , which accounts for the observed enhanced photocurrent and photovoltage of the hybrid solar cells. As a result, the efficiency of P3HT/CdSe QDs/TiO 2 NRAs hybrid cell is greatly higher than that of P3HT/TiO 2 NRAs based cell.

Amorphous GeS x (x = 2, 4, 6) films were prepared by the pulsed laser deposition (PLD) technique. The optical band gaps ( E g opt ) and refractive indices of the films were obtained from the optical absorption spectra and transmission spectra, respectively. The short-wave absorption edges of the films were described using the ‘non-direct transition’ model proposed by Tauc. The dispersion of the refractive index was analyzed in terms of the single-oscillator Wemple–Di Domenico model. The structural units of the films were characterized using Raman spectroscopy. In addition to the basic structural units of edge-sharing and corner-sharing [GeS 4 ] tetrahedra, there are S–S homopolar bonds in S-rich GeS 4 and GeS 6 films while Ge–Ge bonds exist in stoichiometric GeS 2 film. The results show that the index of refraction decreases while E g opt increases with the sulphur content in the GeS x films. The changes of E g opt were discussed in relation to the structure of GeS x films, which were confirmed by the Raman spectra analysis.

Amorphous (GeSe2)100−x –Bi x (x=0, 0.4, 2 and 4) films were prepared by the pulsed laser deposition technique. The optical transmission spectra, absorption spectra and Raman spectra of the films were measured. The short-wavelength absorption edges in the strong absorption region of the films were described using the ‘non-direct-transition’ model proposed by Tauc and the optical band gaps (\(E_{\mathrm{g}}^{\mathrm{opt}})\) were determined. The Urbach energy (E u) was derived in the exponential part of the absorption edge. Both \(E_{\mathrm{g}}^{\mathrm{opt}}\) and Tauc slopes (B 1/2) decreased with increasing Bi content, while E u had the opposite trend. The refractive indices of the films were calculated from the transmission spectra by using the Swanepoel method. Analysis of Raman spectra and absorption spectra shows that Bi addition decreases the mean bond energy and increases E u in the amorphous films, which caused the decrease of \(E_{\mathrm{g}}^{\mathrm{opt}}\). The changes of the refractive indices are also discussed.

Ba0.7Sr0.3TiO3 (BST) thin films were deposited on Pt and SrRuO3(SRO)/Pt hybrid bottom electrodes by radio frequency magnetron sputtering. X-ray analysis indicated that both films were polycrystalline. Dielectric measurements showed that the films on SRO/Pt hybrid bottom electrode had lower dielectric constant and loss than the films on single Pt and the dielectric properties were frequency-independent. The leakage current density of Ba0.7Sr0.3TiO3 thin films on hybrid bottom electrode was also lower. Leakage mechanism investigations showed that the contact between the electrode-film interfaces of thin films on SRO/Pt hybrid bottom electrode was ohmic. Based on the results, the effects of SRO/Pt hybrid bottom electrode on the crystallization and electrical properties of BST thin films were discussed.

Amorphous thin films (1 − x )(4GeSe 2 –Ga 2 Se 3 )– x KBr ( x = 0, 0.1, 0.2, 0.3) were prepared by the pulsed laser deposition (PLD) technique. The optical parameters were calculated using the Swanepoel method from the optical transmission spectra. The optical band gap ( E g opt ) of the studied films increased while the index of refraction decreased when increased the content of KBr. The Tauc slopes were discussed as an indicator of the degree of structural randomness of amorphous semiconductors. The index of refraction decreased and E g opt increased after annealing of as-deposited films below the glass transition temperature. The thermal-bleaching and thermal- contraction effects were observed, which are discussed in relation to the reduction in the density of homopolar bonds confirmed by the Raman spectra analysis and the decreased amount of fragments of the as-deposited films, respectively.

IR transparent bulk-crystallized chalcogenide glasses purely containing nontoxic and excellent nonlinear optical crystallites AgGaGeS4 were fabricated through careful ceramization process of the as-prepared glasses with the composition 53GeS2·47AgGaGeS4 at a temperature of 350 °C for various durations. The second-order optical nonlinearity of bulk-crystallized chalcogenide glasses was discussed on the basis of Maker fringe theory. A large second-order optical nonlinearity (for λ = 1064 nm) up to 5.79 pm/V, was evaluated in the IR transparent chalcogenide glass bulk-crystallized for 24 h.

Ba 0.65 Sr 0.35 TiO 3 (BST) thin films doped with Ho 3+ were prepared on silicon substrates by a modified sol–gel technique. The microstructure of the BST films was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The results showed that 3 mol% Ho-doped BST has the largest grain size and surface root-mean square roughness. The thickness of the film was about 1.36 μm. The Ho 3+ luminescence intensity reached a maximum value in the sample with 3 mol% Ho 3+ ions concentration sintered at 700 °C. All the results showed that the BST: Ho 3+ films may have potential use for photonic devices.

Sol-gel-derived Ba"0"."6"5Sr"0"."3"5TiO"3 (BST) thin films were etched in CF"4/Ar/O"2 plasma using magnetically enhanced reactive ion etching technology. The maximum etch rate of BST film is 8.47nm/min when CF"4/Ar/O"2 gas mixing ratio is equal to 9/36/5. X-ray photoelectron spectroscopy analysis indicates the accumulation of fluorine-containing by-products on the etched surface due to their poor volatility, resulting in (Ba,Sr)-rich and (Ti,O)-deficient etched surface. Compared to the unetched counterparts, the etched Ba 3d"5"/"2, Ba 3d"3"/"2, Sr 3d"5"/"2, Sr 3d"3"/"2, Ti 2p"3"/"2, Ti 2p"1"/"2 and O 1s photoelectron peaks shift towards higher binding energy regions by amounts of 1.31, 1.30, 0.60, 0.79, 0.09, 0.46 and 0.50eV, respectively. X-ray diffraction (XRD) analysis reveals that intensities of the etched BST (100), (110), (200) and (211) peaks are lowered and broadened. Raman spectra confirm that the Raman peaks of the etched film shift towards lower wave number regions with the values of 7, 6, 4 and 4cm^-^1, and the corresponding phonon lifetimes are longer than those of the unetched film because of the plasma-induced damage. When the etched films are postannealed at 650^oC for 20min under an O"2 ambience, the chemical shifts of Ba 3d, Sr 3d, Ti 2p and O 1s peaks, the variations for atomic concentrations of Ba, Sr, Ti and O, and the Raman redshifts are reduced, while the corresponding XRD peak intensities increase. It is conceivable that the plasma-induced damage of the etched film could be partially recovered during the postannealing process.

Ba"0"."6"5Sr"0"."3"5TiO"3 (BST) thin films doped with holmium were prepared on silicon and fused quartz substrates by a modified sol-gel technique. The microstructures of BST films were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The results showed that 3mol% Ho-doped BST has the largest grain size and surface root-mean square roughness. The transmission spectra of Ho-doped BST films were measured by spectrophotometer. The refractive index and thickness of 1mol% Ho-doped BST film was calculated using envelope method from the transmission spectra. It showed that the refractive index increased from 1.94 to 2.09 as wavelength decreased from 700nm to 400nm, which was smaller than pure BST thin films we have reported. The average oscillator strength and wavelength were estimated using a Sellmeir-type dispersion equation. These results show the potential of using Ho-doped BST thin films as an electro-optical novel material.

La0.67Sr0.33MnO3 (LSMO) films were prepared on SrTiO3 single-crystal substrates by the pulsed laser deposition method. X-ray photoelectron spectra (XPS) were measured for the LSMO films as-prepared, annealed in oxygen and in vacuum, respectively. Multiple peaks fitting for Mn 2p3/2 XPS spectra shows that Mn2+ appears and the ratio of Mn3+/Mn4+ increases on the surface of LSMO film annealed in vacuum comparing with the as-prepared film, though the saturation magnetization (Ms) changes little. Mn6+ and Mn7+ can be detected while Mn4+ decreases much on the surface of LSMO film annealed in oxygen. The change of Mn3+/Mn4+ results in the obviously reduce of Ms. O1s spectra show the gradual changes of Mn-O, Sr-O and La-O. Analysis indicates that Mn2+ forms at the surface defects of LSMO films. Annealing in vacuum hardly affects the magnetic property of LSMO films. But annealing in oxygen greatly changes the valence states of Mn, which weakens the magnetic property of LSMO films.

Tunneling electroresistance (TER) effect was investigated in Pt/MgO/Pt/PbTiO3/Pt ferroelectric tunnel junctions (FTJs) theoretically. Compared to Pt/MgO/PbTiO3/Pt FTJs with the same composite barrier thickness (unit cells), FTJs with a thicker Pt interlayer (2 ∼ 3 unit cells) could provide 1 ∼ 6 orders of magnitude improvement in the TER ratio in a wide range of polarization. Resonant tunneling effect and/or enhanced asymmetry of the potential energy profile induced by the resonant-tunneling structure of MgO/Pt/PbTiO3 in Pt/MgO/Pt/PbTiO3/Pt FTJs is responsible for the TER improvement.

20-nm-thickness epitaxial BaTiO3 (BTO) thin films were prepared on the Nb-doped SrTiO3 single-crystal substrates by RF magnetron sputtering technology. The rectifying characteristic current-voltage curves were observed and was discussed using the Schottky barrier model taking into account the movement of oxygen vacancies. The leakage current mechanisms were interpreted by the Schottky emission and Poole-Frenkel emission near the Pt/BTO interface at lower bias and higher bias, respectively.