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Security inks based on photoluminescent materials are mostly investigated for security applications, such as information encryption and decryption, anti‐counterfeiting, and data storage. Although they are invisible to the naked eye under ambient light, they can be detected under ultraviolet or near‐infrared light. Herein, a new kind of secret paper made from network‐structured ultralong hydroxyapatite nanowires and cellulose fibers has been developed. White vinegar, a common cooking ingredient, is used as an invisible security ink. Covert information on the secret paper written with white vinegar is totally invisible under natural light, but it can be decrypted and clearly read after exposure to fire; the response time to fire is short (<10 s). The ways of writing on the secret paper are diverse by using various pens loaded with white vinegar. [ABSTRACT FROM AUTHOR]

As promising fresh‐water purification devices, solar steam generation systems have attracted significant attention recently. However, in practice, the approach often suffers from a poor solar energy conversion efficiency and a low water production rate due to poor material selection and inefficient microscopic structure design. Here, we fabricate an efficient solar steam generation system by "building" polyoxometalate "nano‐walls" on rice paper‐derived three‐dimensional porous carbon paper. In this solar steam generation system, the height of the vertically aligned CoP4Mo6 "nano‐walls" range from 100 to 150 nm with thicknesses about 15 to 25 nm. Under 1 sun irradiation (1 sun = 1 kW m−2), the surface temperature increases from 29 to 50 °C in a short time with a solar thermal conversion efficiency achieving 92.8 %. The stability and durability of this solar steam generation system, which withstands fifteen cycle continuous tests, also offer good prospects. Its attractive solar energy conversion performance originates from the intense sunlight absorption and high conversion ability of the CoP4Mo6 "nano‐walls", as well as extremely promising heat localization and water transportation properties of the three‐dimensional porous carbon paper. This solar steam generation system, which has produced some inspiring results, is employed for seawater desalination and for purification of water polluted with organic dyes. [ABSTRACT FROM AUTHOR]

In this concept, we showcase the upsurge in the studies of dynamic ultralong room‐temperature phosphorescence (RTP) materials containing inorganic and/or organic components as versatile photo‐responsive platforms. The goal is to provide a comprehensive analysis of photo‐controllable RTP, and meanwhile delve into the underlying RTP properties of various classes of photochromic materials including metal‐organic complexes, organic‐inorganic co‐crystals, purely organic small molecules and organic polymers. In particular, the design principles governing the integration of the photochromic and RTP moieties within a single material system, and the tuning of dynamic RTP in response to light are emphasized. As such, this concept sheds light on the challenges and opportunities of using these tunable RTP materials for potential applications in optoelectronics, particularly highlighting their use of reversible information encryption, erasable light printing and rewritable smart paper. [ABSTRACT FROM AUTHOR]

Electric‐driven conversion of carbon dioxide (CO2) to carbon monoxide (CO) under mild reaction conditions offers a promising approach to mitigate the greenhouse effect and the energy crisis. Surface engineering is believed to be one of the prospective methods for enhancing the electrocatalytic activity of CO2 reduction. Herein, hydroxyl (OH) groups were successfully introduced to cadmium nanosheets to form cadmium and cadmium hydroxide nanocomposites (i. e. Cd/Cd(OH)2 nanosheets) via a facile two‐step method. The as‐prepared Cd/Cd(OH)2/CP (CP indicates carbon paper) electrode displays excellent electrocatalytic activity for CO2 reduction to produce CO. The Faradaic efficiency of CO reaches 98.3 % and the current density achieves 23.8 mA cm−2 at −2.0 V vs. Ag/Ag+ in a CO2‐saturated 30 wt% 1‐butyl‐3‐methylimidazole hexafluorophosphate ([Bmim]PF6)‐65 wt% acetonitrile (CH3CN)‐5 wt% water (H2O) electrolyte. And the CO partial current density can reach up to 71.6 mA cm−2 with the CO Faradaic efficiency of more than 85 % at −2.3 V vs. Ag/Ag+, which stands out against Cd/CP, Cd(OH)2/CP, and Cd/CdO/CP electrodes. The excellent electrocatalytic performance of the Cd/Cd(OH)2/CP electrode can be attributed to its unique structural properties, suitable OH groups, perfect interaction with electrolyte, abundant active sites and fast electron transfer rate. [ABSTRACT FROM AUTHOR]

An innovative method for making a new kind of highly flexible, fireproof, inorganic, nanocomposite paper made from glass fibers (GFs) coated with network-structured hydroxyapatite ultralong nanowires (NS-HANWs) is reported. The NS-HANW/GF paper is fireproof, high-temperature resistant, highly flexible, highly exquisite, and smooth, which is comparable to high-quality advanced coated paper. The most incredible characteristic of the NS-HANW/GF paper is its incombustibility. The as-prepared NS-HANW/GF paper, with the addition of optimized inorganic additives, has high mechanical properties (tensile strength ≈16 MPa) and the tensile strength is nearly 15 times that of GF paper. In addition, the NS-HANW/GF paper exhibits a high biocompatibility, owing to the coating effect of NS-HANWs on GFs. Thermal analysis indicates that the NS-HANW/GF paper has high thermal stability at high temperatures up to 1000 °C. Competitive to conventional insulation materials, the NS-HANW/GF paper exhibits a low thermal conductivity and excellent heat insulation performance. Experiments show that the NS-HANW/GF paper is promising for application in the protection layer of fire-retardant fiber-optic cable. The NS-HANW/GF paper can also be used as printing, copying, or writing paper; nonflammable China paper; fire-retardant wallpaper; specialty fireproof paper; and so on. [ABSTRACT FROM AUTHOR]

Deposition of redox‐active metal–organic frameworks (MOFs) as thin films on conductive substrates is of great importance to improve their electrochemical performance and durability. In this work, a series of metalloporphyrinic MOF crystals was successfully deposited as thin films on carbon fiber paper (CFP) substrates, which is an alternative to rigid glass substrates. The specific dimensions of the obtained films could be adjusted easily by simple cutting. Metalloporphyrinic MOFs on CFP with different active metal species have been employed for electrochemical conversion of the carcinogenic nitrite into the less toxic nitrate. The MOFs on CFP exhibit remarkable improvement in terms of the electrocatalytic performance and reusability compared with the electrodes prepared from MOF powder. The contribution from metal species of the porphyrin units and reaction mechanisms was elucidated based on the findings from X‐ray photoelectron spectroscopy (XPS) and in situ X‐ray absorption near edge structure (XANES) measured during the electrochemical reaction. By integrating the redox‐active property of metalloporphyrinic MOFs and high conductivity of CFP, MOF thin films on CFP provided a significant improvement of electrocatalytic performance to detoxify the carcinogenic nitrite with good stability. [ABSTRACT FROM AUTHOR]

Developing a straightforward and effective hydrophobic modification for metal−organic frameworks (MOFs) under mild conditions is meaningful for MOF applications. Here, a post‐synthetic modification approach assisted with metal hydroxyl groups at room temperature is reported to induce hydrophobicity in the hydrophilic UiO‐66. The bonding between Zr−OH in UiO‐66 and n‐tetradecylphosphonic acid (TDPA) is the vital force for the modifier TDPA. Superhydrophobic and superoleophilic composites were constructed for efficient oil‐water separation by coating TDPA‐modified UiO‐66 (P‐UiO‐66) on commercial melamine sponges (MS) and filter papers (FP) with water contact angles of 153.2° and 155.6°, respectively. The P‐UiO‐66/MS composite could quickly and selectively absorb oily liquids up to 43 times its weight from water. The P‐UiO‐66/MS achieved continuous oil collection with high separation efficiencies (≥99.4 %). In addition, P‐UiO‐66/FP and P‐UiO‐66/MS showed high separation efficiencies for water‐in‐oil emulsions (≥98.5 %) and oil‐in‐water emulsions, respectively, with high resistance to low/high temperatures and acid/base conditions. The metal hydroxyl group‐assisted post‐synthetic modification strategy offers a facile and broad way to prepare hydrophobic MOFs for promising applications in environmental fields. [ABSTRACT FROM AUTHOR]

A single amino acid in a peptide sequence can play an important role to tune the self‐assembly and hydrogelation behaviour. Here, a C‐terminal cysteine‐containing ultrashort peptide hydrogelator forms hydrogel through non‐covalent and covalent interactions. Interestingly, the hydrogel is insoluble in water and buffer solutions at different pH values (1‐13) and is thixotropic and injectable. In recent years, removing dyes from contaminated water has become a significant concern because of the shortage of freshwater resources. Therefore, the adsorption of dyes through a reliable, straightforward, nontoxic, cheap, and environmentally friendly adsorbent has become a popular topic. Hence, the hydrogelator was exploited to remove organic dyes from wastewater, harnessing its applicability in the gel phase and solid supports (filter paper and cotton). [ABSTRACT FROM AUTHOR]

A highly flexible and nonflammable inorganic hydroxyapatite (HAP) paper made from HAP ultralong nanowires is reported. The paper can be used for printing and writing and is promising for the permanent and safe storage of information, such as archives and important documents. The HAP paper is also an excellent and recyclable adsorbent for organic pollutants. [ABSTRACT FROM AUTHOR]

Abstract: Increasing counterfeiting of important data, currency, stamp papers, branded products etc., has become a major security threat which could lead to serious damage to the global economy. Consequences of such damage are compelling for researchers to develop new high‐end security features to address full‐proof solutions. Herein, we report a dual mode flexible highly luminescent white security paper and nanotaggants composed of nanophosphors incorporated in polymer matrix to form a nanofiber‐based mat for anti‐counterfeiting applications. The dual mode nanofibers are fabricated by electrospinning technique by admixing the composite of NaYF4:Eu3+@NaYF4:Yb3+, Er3+ nanophosphors in the polyvinyl alcohol solution. This flexible polymer mat derived from nanofibers appears white in daylight, while emitting strong red (NaYF4:Eu3+) and green (NaYF4:Yb3+, Er3+) colors at excitation wavelengths of 254 nm and 980 nm, respectively. These luminescent nanofibers can also be encrypted as a new class of nanotaggants to protect confidential documents. These obtained results suggest that highly luminescent dual mode polymeric nanofiber‐based flexible white security paper and nanotaggants could offer next‐generation high‐end unique security features against counterfeiting. [ABSTRACT FROM AUTHOR]