[en] Graphical abstract: The changes in open-circuit-potential of X65 steel in 0.5 M NaHCO_3 solution in CO_2 at 50 °C and 0.7 MPa. - Highlights: • X65 steel was passivated in 0.5 M NaHCO_3 solution in CO_2 at 0.7 MPa and 50 °C. • OCP of X65 steel appreciably shifted toward the noble direction. • Disordered precipitation containing the elements Fe Na and O on the surface of the FeCO_3 film was observed. • The precipitation of disordered substance elevated OCP. - Abstract: In this study, the use of NaHCO_3 as a pH stabilizer for the corrosion control of X65 (UNS K03014) carbon steel in different environments was experimentally investigated. The experiments were conducted at room temperature and at 50 °C in 0.5 M NaHCO_3 solutions purged with CO_2. Electrochemical tests were conducted in a high-pressure, high-temperature autoclave. The constituents of the corrosion products were investigated through scanning electron microscopy and X-ray diffraction. The results showed that X65 steel can be passivated in 0.5 M NaHCO_3 solution in a CO_2 environment. Immersion in 0.5 M NaHCO_3 solution in a high-pressure, high-temperature autoclave resulted in the formation of a dense corrosion film on the surface of the X65 steel.

[en] Immersion tests, electrochemical measurements and surface characterizations (Scanning electron microscopy, Energy dispersive spectroscopy, Laser scanning confocal microscope) were used to study the corrosion behavior of a 3Cr low alloy pipeline steel welded joint in CO₂-saturated oilfield formation waters. The formation mechanism of the corrosion scale was discussed with in situ pH monitoring of various regions in the welded joint. In the initial stage of corrosion, the lowest potential and the highest corrosion rate were found on the base metal (BM). After the immersion of 120 h, the heat affected zone (HAZ) underwent the slightest corrosion, which may be related to the formation of a dense compact outer layer (mainly composed of FeCO₃) on the HAZ. In pH monitoring tests, the HAZ showed a higher pH level than the BM, which favored the nucleation of FeCO₃ and led to much more FeCO₃ deposition on the HAZ. (paper)

[en] Highlights: • We employed CsSnX₃ for Pb²⁺ via cation replacement for the first time. • Lead-free perovskite has the linear range and high selectivity. • The CsSnBr₃ QDs was successfully applied to detect Pb²⁺ in organic products. -- Abstract: Lead ion is one of the most toxic metallic pollutants, lacking of photoluminescence probe in organic products. In this work, the lead free perovskite CsSnX₃ (X = Cl, Cl/Br, or Br) quantum dots (QDs) were employed as a novel fluorescent probe for the detection of lead ion in the oily products, with high sensitivity and high selectivity. The highly enhanced photoluminescence, the red shift and the reduction of the full wavelength at half maximum (FWHM) of emission spectra of CsSnX₃ QDs were observed after adding Pb²⁺ ions, originating from the substitution of Sn²⁺ by Pb²⁺ ions in situ. A wide dynamic range from 1 × 10⁻⁸ M to 1 × 10⁻² M and a low limit of detection (3.5 × 10⁻⁹ M) were obtained. Finally, the CsSnBr₃ QDs was successfully employed to probe Pb²⁺ ions in mask, hair dye, nail polish and oil paint. Our probe provides a promising device to detect Pb²⁺ ions in organic solution system.

[en] Carbon dots (CDs) are the promising candidates for application in optoelectronic and biological areas due to their excellent photostability, unique photoluminescence, good biocompatibility, low toxicity and chemical inertness. However, the self-quenching of photoluminescence as they are dried into the solid state dramatically limits their further application. Therefore, realizing efficient photoluminescence and large-scale production of CDs in the solid state is an urgent challenge. Herein, solid-state hybrid nanofibers based on CDs and polyvinylpyrrolidone (PVP) are constructed through an electrospinning process. The resulting solid-state hybrid PVP/CD nanofibers present much enhanced photoluminescence performance compared to the corresponding pristine colloidal CDs due to the decrease in non-radiative recombination of electron–holes. Owing to the suppressed self-quenching of CDs, the photoluminescence quantum yield is considerably improved from 42.9% of pristine CDs to 83.5% of nanofibers under the excitation wavelength of 360 nm. This has great application potential in optical or optoelectronic devices. (paper)

[en] Inorganic perovskite quantum dots (QDs) have attracted wide attention in display and solid-state lighting because of their easily tunable band-gaps and high photoluminescence quantum yields (PLQY) of green light emission. However, some drawbacks limit their practical applications, including the low PLQY of blue light emission and the instability in the moisture environment. In this work, efficient blue-light emitting CsPbBr₃ perovskite QDs with PLQY of 72% were developed through a bandgap engineering approach. The achieved blue-light emitting PLQY is much higher than the values acquired in the inorganic perovskite QDs in the literature. And the emission color of the as-prepared QDs can be facially tuned by only adjusting the reaction temperature. Further, the mono-dispersed perovskite QDs@SiO₂ composites were constructed benefiting from the low temperature synthesis. The optical performance of the QDs could be well persisted even in the moisture environment. Finally, the as-prepared QDs@SiO₂ composite was fabricated as the QD ink on the anti-counterfeit printing technology, from which the obtained pattern would emit varied color under UV lamp. And the as-prepared composites was also applied for fabricating WLED, with Commission Internationale de l’Eclairage (CIE) color coordinates of (0.33, 0.38) and power efficiency of 32.5 lm W⁻¹, demonstrating their promising potentials in solid-state lighting. (paper)

[en] Carbon dots (CDs), one of the most significant classes of carbon-based nanophosphors, have attracted extensive attention in recent years. However, few attempts have been reported for realizing CDs with tunable emissions, especially for obtaining the red-light emissions with high photoluminescence quantum yields. Herein, we synthesized CDs with different chromatic blue, green and red emissions by facilely changing the reaction solvent during hydrothermal conditions. The photoluminescence quantum yields of 34%, 19% and 47% for the blue, green and red emissions, respectively, were achieved. Furthermore, the solid-state CD/PVA composite films were constructed through mixing the CDs with PVA polymer, in which the self-quenching of photoluminescence of CDs had been successfully avoided benefiting from the formation of hydrogen bonds between the CDs and PVA molecules. Finally, the warm white light emitting diode (WLED) was fabricated by integrating CD/PVA film on a UV-LED chip. The WLED exhibited the Commission International de l’Eclairage coordinates (CIE) of (0.38, 0.34), correlated color temperature of 3913 K and color rendering index of 91, respectively, which were comparable with the commercial WLEDs. (paper)

[en] Carbon dots (CDs) have emerged as a new type of fluorescent material because of their unique optical advantages, such as high photoluminescence quantum yields (QYs), excellent photo-stability, excitation-dependent emissions, and low toxicity. However, the photoluminescence mechanism for CDs remains unclear, which limits their further practical application. Here, CDs were synthesized via a solvothermal route from citric acid and urea. Through the oxidation and reduction treatment of pristine CDs, the origin of the photoluminescence and the involved mechanism were revealed. We found that the blue/green/red emissions originated from three diverse emitting states, i.e. the intrinsic state, and C=O- and C=N-related surface states, respectively. Based on the as-prepared CDs, a pH sensor depending on the radiometric luminescence detection was developed. Furthermore, we constructed CD/PVP (PVP, polyvinylpyrrolidone) composite films, which exhibited white light emission with photoluminescence QYs of 15.3%. The white light emission with different correlated color temperatures (CCTs), from 4807 K to 3319 K, was obtained by simply changing the amount of PVP solution. Benefiting from the white light-emitting solid-state films, single-component white light-emitting diodes were fabricated with an average color rendering index value (Ra) of 80.0, luminous efficiency of 10.2 lm W⁻¹, and good working stability, thus indicating a promising potential for practical lighting applications. (paper)

[en] Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln${}^{3+}$) ions doped Cs${}_2$M (In${}_{0.95}$Sb${}_{0.05}$)Cl${}_6$ (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs${}_2$M (In${}_{1-<!--\; ???\; -->x}$Sb${}_x$)Cl${}_6$ NCs can break the forbidden of f-f transition of Ln${}^{3+}$, thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln${}^{3+}$. Finally, the wide-coverage NIR LEDs based on Sm${}^{3+}$, Nd${}^{3+}$, Er${}^{3+}$-tridoped Cs${}_2$K${}_{0.5}$Rb${}_{0.5}$(In${}_{0.95}$Sb${}_{0.05}$)Cl${}_6$ NCs are fabricated and employed in the multiplex gas sensing and night-vision application. (© 2023 Wiley‐VCH GmbH)

[en] Highlights: • Weldability of novel 3Cr pipeline steel was investigated using two commercial and an inhouse welding wires. • Mechanical properties were measured and microstructure characteristics were observed. • Fracture positions of tensile test just corresponded to the minimum hardness region of the joints. • The inhouse wire R01 can provide the highest cost-performance ratio. - Abstract: The welded joints of the novel 3Cr pipeline steel were fabricated via the gas tungsten arc welding (GTAW) technique using an inhouse welding wire labeled as R01 and two kinds of commercial wires (H08Cr3MoMnA and TGS-2CML). Microhardness, impact toughness and tensile properties of the joints were measured, and microstructure characteristics were observed by scanning electron microscopy (SEM). The results show that under selected welding procedure, the joints of R01 can achieve quite good mechanical properties without preheating and post weld heat treatment (PWHT). After thermal refining, elongation (15.2%) doubled and met the DNV-OS-F101 standard. For low carbon or super low carbon pipeline steels such as 3Cr steel, the revised formula with the carbon applicable coefficient (A(c)) was quite good for predicting the maximum hardness in heat affected zone (HAZ). Compared with these two selected commercial wires, the inhouse welding wire R01 can provide the highest cost-performance ratio

[en] Highlights: • The corrosion behavior of 13Cr steel exposed to bromine salt completion fluid containing high concentration bromine ions was investigated. • There are passive circles around pits on the 13Cr steel surface after 7 d of exposure. • Macroscopic galvanic corrosion formed between the passive halo and the pit. • The mechanism of pitting corrosion on 13Cr stainless steel exposed to heavy bromine brine was established. - Abstract: A series of corrosion tests of 13Cr stainless steel were conducted in a simulated completion fluid environment of high temperature and high concentration bromine salt. Corrosion behavior of specimens and the component of corrosion products were investigated by means of scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicate that 13Cr steel suffers from severe local corrosion and there is always a passive halo around every pit. The formation mechanism of the passive halo is established. OH⁻ ligand generates and adsorbs in a certain scale because of abundant OH⁻ on the surface around the pits. Passive film forms around each pit, which leads to the occurrence of passivation in a certain region. Finally, the dissimilarities in properties and morphologies of regions, namely the pit and its corresponding passive halo, can result in different corrosion sensitivities and may promote the formation of macroscopic galvanic pairs