Realization of Structural Colors via Capped Cu-based F-P Cavity Structure.

Structural colors with tunable properties have several applications in the beautification of mobile devices, surface decoration, art and color filters. Herein, we propose an asymmetric F-P cavity design to systematically tune structural colors by changing the thickness of the top metal and intermediate insulator. In this study, Cu and Si3N4 were chosen as the top metal and intermediate insulator layers, respectively, various reflection colors being realized on the Cu surface. Various capping layers-that is, SiO2, polymethyl methacrylate (PMMA), and a commercially available clear coat named ProtectaClear-were used to protect the Cu surface from scratching and oxidation. PMMA coatings can protect Cu from corrosive environments without degradation of the color quality. The colors can be tuned by controlling the thickness of either the metal or intermediate insulator layers, and vivid structural colors-including orange, bright orange, red, purple, violet, light blue, green-yellow, and yellow-green-can be printed. The colors obtained can be attributed to thin-film interference.

Unexpected Roles of Interstitially Doped Lithium in Blue and Green Light Emitting Y2O3:Bi3+: A Combined Experimental and Computational Study.

To enhance the photoluminescence of lanthanide oxide, a clear understanding of its defect chemistry is necessary. In particular, when yttrium oxide, a widely used phosphor, undergoes doping, several of its atomic structures may be coupled with point defects that are difficult to understand through experimental results alone. Here, we report the strong enhancement of the photoluminescence (PL) of Y2O3:Bi3+ via codoping with Li+ ions and suggest a plausible mechanism for that enhancement using both experimental and computational studies. The codoping of Li+ ions into the Y2O3:Bi3+ phosphor was found to cause significant changes in its structural and optical properties. Interestingly, unlike previous reports on Li+ codoping with several other phosphors, we found that Li+ ions preferentially occupy interstitial sites of the Y2O3:Bi3+ phosphor. Computational insights based on density functional theory calculations also indicate that Li+ is energetically more stable in the interstitial sites than in the substitutional sites. In addition, interstitially doped Li+ was found to favor the vicinity of Bi3+ by an energy difference of 0.40 eV in comparison to isolated sites. The calculated DOS showed the formation of a shallow level directly above the unoccupied 6p orbital of Bi3+ as the result of interstitial Li+ doping, which may be responsible for the enhanced PL. Although the crystallinity of the host materials increased with the addition of Li salts, the degree of increase was minimal when the Li+ content was low (<1 mol %) where major PL enhancement was observed. Therefore, we reason that the enhanced PL mainly results from the shallow levels created by the interstitial Li+.

Photoluminescence properties of lead selenide produced by selenization and a solvothermal method.

We studied temperature-dependent photoluminescence (PL) spectra of lead selenide (PbSe) dendrites and cubes grown by a solvothermal method. Their PL peaks were located at ∼8 µm at 10 K with a full width at half maximum (FWHM) of 10 meV. Using the temperature-dependent FWHM values, we obtained carrier-phonon coupling coefficients for PbSe. We also demonstrated mechanochemical synthesis of polycrystalline PbS nanoparticles and their successful conversion into a PbSe layer composed of nanocrystals by a selenization process with thermal treatment. The nanocrystals were found to be formed by the orientation alignment of small grains in the process. The PL peak energies of the PbSe layers as well as the PbSe dendrites and the cubes agreed well with their absorption edges in the transmission spectra, indicating that the photoluminescence originates from the band-edge emission. The band-edge emissions hold promise for the development of potential mid-infrared light sources using PbSe fabricated by these methods.

Chitosan-Based Structural Color Films for Humidity Sensing with Antiviral Effect.

This scientific investigation emphasizes the essential integration of nature's influence in crafting multifunctional surfaces with bio-inspired designs for enhanced functionality and environmental advantages. The study introduces an innovative approach, merging color decoration, humidity sensing, and antiviral properties into a unified surface using chitosan, an organo-biological polymer, to create cost-effective multilayered films through sol-gel deposition and UV photoinduced deposition of metal nanoparticles. The resulting chitosan films showcase diverse structural colors and demonstrate significant antiviral efficiency, with a 50% and 85% virus inhibition rate within a rapid 20 min reaction, validated through fluorescence cell expression and real-time qPCR (polymerase chain reaction) assays. Silver-deposited chitosan films further enhance antiviral activity, achieving remarkable 91% and 95% inhibition in independent assays. These films exhibit humidity-responsive color modifications across a 25-90% relative humidity range, enabling real-time monitoring validated through simulation studies. The proposed three-in-one functional surface can have versatile applications in surface decoration, medicine, air conditioning, and the food industry. It can serve as a real-time humidity sensor for indoor and outdoor surfaces, find use in biomedical devices for continuous humidity monitoring, and offer antiviral protection for frequently handled devices and tools. The customizable colors enhance visual appeal, making it a comprehensive solution for diverse applications.

Preparation of monolithic cu(In0.7Ga0.3)Se2 nanopowders and subsequent fabrication of sintered CIGS films.

Cu(In,Ga)Se2 (CIGS) is a compound semiconductor and is one of the most attractive light-absorbing materials for use in thin film solar cells. Among the various approaches to prepare CIGS thin films, the powder process offers an extremely simple and materials-efficient method. Here, we report the mechano-chemical preparation of CIGS compound powders suitable for fabrication of CIGS films by a powder process. We found that the CIGS phase was formed from the elemental powders of Cu, In, and Se and liquid Ga using high energy milling process with a milling time as short as 40 min at 200 rpm due to a self-accelerating exothermic reaction. The morphology and size of the CIGS powders changed with a function of the milling speed (100-300 rpm), leading to an optimal condition of milling at 200 rpm for 120 min. We also found that it was difficult to obtain a monolithic phase of the CIGS powders without severe particle aggregation by mechano-chemical milling alone. Therefore, in combination with the milling, subsequent heat-treatment at 300 degrees C was performed, which successfully provided monolithic CIGS nanopowders suitable for powder process. When a thin film was fabricated from the monolithic CIGS nanopowders, a highly dense film with large crystalline grains was obtained. The CIGS film preserved its chemical composition of CuIn0.7Ga0.3Se2 after sintering as evidenced by Raman spectroscopy, EDS and SAED pattern of transmission electron microscopy. The film was also found suitable for a light absorbing layer of CIGS solar cells with its band gap energy of 1.14 eV evaluated by transmittance spectroscopy.

Efficient Fluoride Wastewater Treatment Using Eco-Friendly Synthesized AlOOH.

Fluoride ion is essential for health in small amounts, but excessive intake can be toxic. Meeting safety regulations for managing fluoride ion emissions from industrial facilities with both cost-effective and eco-friendly approaches is challenging. This study presents a solution through a chemical-free process, producing a boehmite (AlOOH) adsorbent on aluminum sheets. Utilizing cost-effective Al foil and DI water, rather than typical precursors, yields a substantial cost advantage. The optimized AlOOH adsorbent demonstrated a high fluoride ion removal rate of 91.0% in simulated wastewater with fluoride ion concentrations below 20 ppm and displayed a similar performance in industrial wastewater. Furthermore, the AlOOH adsorbent exhibited excellent reusability through a simple regeneration process and maintained stable performance across a wide pH range of 4 to 11, demonstrating its capability to adsorb fluoride ions under diverse conditions. The efficiency of the AlOOH adsorbent was validated by a high fluoride ion removal efficiency of 90.9% in a semi-batch mode flow cell, highlighting its potential applicability in engineered water treatment systems. Overall, the AlOOH adsorbent developed in this study offers a cost-effective, eco-friendly, and sustainable solution for effectively removing fluoride ion from surface waters and industrial wastewaters.

Performance Enhancement in Powder-Fabricated Cu2(ZnSn)Se4 Solar Cell by Roll Compression.

Despite the improved conversion efficiency of Cu2(ZnSn)Se4 (CZTSe) solar cells, their roll-to-roll fabrication nonetheless leads to low performance. The selenization time and temperature are typically considered major parameters for a powder-based CZTSe film; meanwhile, the importance of the densification during the roll-to-roll process is often overlooked. The densification process is related to the porosity of the light-absorbing layer, where high porosity lowers cell performance. In this study, we fabricated a dense CZTSe absorber layer as a method of controlling the compression of a powder precursor (Cu1.7(Zn1.2Sn1.0)S4.0 (CZTS)) during the roll-press process. The increased particle packing density of the CZTS layer was crucial in sintering the powder layer into a dense film and preventing severe selenization of the Mo back electrode. The pressed absorber layer of the CZTSe solar cell exhibited a more uniform chemical composition determined using dynamic secondary ion mass spectrometry (SIMS). Under the AM 1.5G illumination condition, the power conversion efficiency of the pressed solar cell was 6.82%, while the unpressed one was 4.90%.

In Situ Metal Deposition on Perhydropolysilazane-Derived Silica for Structural Color Surfaces with Antiviral Activity.

Structural coloration has recently sparked considerable attention on the laboratory and industrial scale. Structural colors can create vivid, saturated, and long-lasting colors on metallic surfaces for optical filters, digital displays, and surface decoration. This study used an all-solution, low-cost method, free of a specific setup procedure, to fabricate structural colors of a multilayered metal-dielectric structure based on interference effects within a Fabry-Perot cavity. The insulating (dielectric) layer was produced from perhydropolysilazane, an inorganic silicon-containing polymer, from which hydrogen was liberated during conversion into silica and applied in situ to reduce metallic nanoparticles on the silica surface. This simple manufacturing technique contributes to the fabrication of large, high-quality surfaces, which could potentially be employed for surface decoration. The fabricated surfaces also exhibited excellent hydrophobic properties with contact angles up to 137°, endowing them with self-cleaning properties. In addition, the antiviral and antibacterial impact of the silver (Ag)/silica (SiO2)/stainless steel (SUS) film was also examined, as Ag has been reported to have antimicrobial and, recently, antiviral properties. According to three independently conducted antiviral assays, the fluorescence expression of virus-infected cells, PCR analysis, and modified tissue culture infectious dose assay, the film inhibited lentivirus by 75, 97, and 99% when exposed to the virus for 20 min, 1 h, and 20 min, respectively. Furthermore, the film had exceptional antibacterial activity with no colony growth observed for 24 and 12 h of inoculation. It is thus conceivable that these structural color-based films can be used to not only decorate metal surfaces with aesthetic colors but also limit virus and bacterium propagation successfully.

Lanthanide and Ladder-Structured Polysilsesquioxane Composites for Transparent Color Conversion Layers.

Ladder-type polysilsesquioxanes (LPSQs) containing phenyl as a high refractive index unit and cyclic epoxy as a curable unit were found to be excellent candidates for a transparent color conversion layer for displays due to being miscible with organic solvents and amenable to transparent film formation. Therefore, the LPSQs were combined with luminescent lanthanide metals, europium Eu(III), and terbium Tb(III), to fabricate transparent films with various emission colors, including red, orange, yellow, and green. The high luminescence and transmittance properties of the LPSQs-lanthanide composite films after thermal curing were attributed to chelating properties of hydroxyl and polyether side chains of LPSQs to lanthanide ions, as well as a light sensitizing effect of phenyl side chains of the LPSQs. Furthermore, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy and nanoindentation tests indicated that the addition of the nanoparticles to the LPSQs moderately enhanced the epoxy conversion rate and substantially improved the wear resistance, including hardness, adhesion, and insusceptibility to atmospheric corrosion in a saline environment. Thus, the achieved LPGSG-lanthanide hybrid organic-inorganic material could effectively serve as a color conversion layer for displays.

Thia-, aza-, and selena[3.3.1]bicyclononane dichlorides: rates vs internal nucleophile in anchimeric assistance.

Sulfur-, selenium-, and nitrogen-containing compounds bearing leaving groups in the ß-position undergo facile substitution chemistry enabled by anchimeric assistance. Here we provide direct comparisons between such systems in the rigid bicyclo[3.3.1]nonane framework easily derived from 1,5-cyclooctadiene. For a series of dichloride electrophiles of this type, the relative reactivities were found to be Se ≫ (alkyl)N > S ≥ (propargyl)N > (phenyl)N, with the reaction rates at the two extremes differing by more than 3 orders of magnitude. For the N-alkyl case, substitution rates were largely independent of the trapping nucleophile but were strongly dependent on solvent, showing that the process is controlled by the formation of the high-energy three-membered cationic intermediate.

Tailored ligand acceleration of the Cu-catalyzed azide-alkyne cycloaddition reaction: practical and mechanistic implications.

Tris(heterocyclemethyl)amines containing mixtures of 1,2,3-triazolyl, 2-benzimidazoyl, and 2-pyridyl components were prepared for ligand acceleration of the copper-catalyzed azide-alkyne cycloaddition reaction. Two classes of ligands were identified: those that give rise to high reaction rates in coordinating solvents but inhibit the process when used in excess relative to copper and those that provide for fast catalysis in water and are not inhibitory in excess. Several "mixed" ligands were identified that performed well under both types of conditions. Kinetics measurements as a function of ligand:metal ratio and catalyst concentration were found to be consistent with an active Cu(2)L formulation. Since strongly bound chelating agents are not always the most effective, achieving optimal rates requires an assessment of the potential donor molecules in the reaction mixture. Simple rules are provided to guide the user in the choice of effective ligands and reaction conditions to suit most classes of substrates, solvents, and concentrations.

Performance Differences of Hexavalent Chromium Adsorbents Caused by Graphene Oxide Drying Process.

In this study, the influence of drying conditions on amine (-NH3) functionalization of graphene oxide (GO) was evaluated, and the hexavalent chromium (Cr(VI)) adsorption efficiency of the prepared materials was compared. 3-[2-(2-aminoehtylamino) ethylamino]propyl-trimethoxysilane (3N) was used for amine functionalization. The synthesized materials were analyzed by SEM, BET, TGA, XPS, and EA. TGA results showed that the solution-GO (SGO) was functionalized by more 3N molecules than freeze-dried GO (FDGO) and oven-dried GO (ODGO). Additionally, XPS analysis also showed that the ratio of N/C and Si/C was relatively high in SGO than FDGO and ODGO. The maximum adsorption capacity of SGO, FDGO, and ODGO for Cr(VI) was 258.48, 212.46, and 173.45 mg g-1, respectively. These results indicate that it is better to use SGO without drying processes for efficient amine functionalization and Cr(VI) removal. However, when the drying process is required, freeze-drying is better than oven-drying.

Control of Particle Size in Flame Spray Pyrolysis of Tb-doped Y2O3 for Bio-Imaging.

Recently, the use of oxide-based nanomaterials for bio-imaging has received great attention owing to their remarkable stabilities as compared to those of conventional organic dyes. Therefore, the development of scalable methods for highly luminescent oxide materials with fine control of size has become crucial. In this study, we suggested modified flame spray pyrolysis (FSP) as a scalable method to produce a green-light emitting phosphor-Tb-doped Y2O3-in the nanometer size range. In our FSP method, an alkali salt (NaNO3) was found to be highly effective as a size-controlling agent when it is simply mixed with other metal nitrate precursors. The FSP of the mixture solution resulted in oxide composites of Y2O3:Tb3+ and NaxO. However, the sodium by-product was easily removed by washing with water. This salt-assisted FSP produced nano-sized and well-dispersed Y2O3:Tb3+ nanoparticles; their crystallinity and luminescence were higher than those of the bulk product made without the addition of the alkali salt. The nanoparticle surface was further coated with silica for biocompatibility and functionalized with amino groups for the attachment of biological molecules.

Most suitable amino silane molecules for surface functionalization of graphene oxide toward hexavalent chromium adsorption.

Adsorption is a simple and effective method for the removal of hexavalent chromium (Cr(VI)) from contaminated water. Several amino silane-graphene oxide (GO) composites with different species of amino groups (pN-GO, psN-GO, and pssN-GO; p: primary, s: secondary, N: amine) were evaluated to investigate their adsorption capacity and the effects of primary and secondary amines on Cr(VI) adsorption. We conducted a quantitative analysis to reveal the difference between primary and secondary amines in terms of Cr(VI) removal efficiency. A synergic effect was observed between the neighboring secondary amines in pssN-GO. From the Langmuir model prediction, we found that the composite with pssN-GO exhibited the highest maximum adsorption capacity (260.74 mg/g), followed by those with psN-GO (208.22 mg/g) and pN-GO (189.47 mg/g). Monolayer adsorption was more dominant when using pssN-GO, with the pseudo-second-order model best fitting the kinetic experiment results, whereas multilayer adsorption was dominant when using psN-GO and pN-GO.

Polyvalent display of heme on hepatitis B virus capsid protein through coordination to hexahistidine tags.

The addition of a hexahistidine tag to the N terminus of the hepatitis B capsid protein gives rise to a self-assembled particle with 80 sites of high local density of histidine side chains. Iron protoporphyrin IX has been found to bind tightly at each of these sites, making a polyvalent system of well-defined spacing between metalloporphyrin complexes. The spectroscopic and redox properties of the resulting particle are consistent with the presence of 80 site-isolated bis(histidine)-bound heme centers, comprising a polyvalent b-type cytochrome mimic.

Optimization of the electron transport in quantum dot light-emitting diodes by codoping ZnO with gallium (Ga) and magnesium (Mg).

In our study, to optimize the electron-hole balance through controlling the electron transport layer (ETL) in the QD-LEDs, four materials (ZnO, ZnGaO, ZnMgO, and ZnGaMgO NPs) were synthesized and applied to the QD-LEDs as ETLs. By doping ZnO NPs with Ga, the electrons easily inject due to the increased Fermi level of ZnO NPs, and as Mg is further doped, the valence band maximum (VBM) of ZnO NPs deepens and blocks the holes more efficiently. Also, at the interface of QD/ETLs, Mg reduces non-radiative recombination by reducing oxygen vacancy defects on the surface of ZnO NPs. As a result, the maximum luminance (L max) and maximum luminance efficiency (LEmax) of QD-LEDs based on ZnGaMgO NPs reached 43 440 cd m-2 and 15.4 cd A-1. These results increased by 34%, 10% and 27% for the L max and 450%, 88%, and 208% for the LEmax when compared with ZnO, ZnGaO, and ZnMgO NPs as ETLs.

Cavity-tailored, self-sorting supramolecular catalytic boxes for selective oxidation.

Using a steric self-sorting strategy, the assembly of highly ordered and rigid supramolecular boxes possessing catalytic properties has been achieved in one step. The formation of these assemblies, comprising up to 18 porphyrin centers, was readily confirmed by solution X-ray scattering in conjunction with fluorescent spectroscopy. Size-selective and enantioselective oxidation catalysis were both demonstrated.

Chromium removal from aqueous solution by a PEI-silica nanocomposite.

It is essential and important to determine the adsorption mechanism as well as removal efficiency when using an adsorption technique to remove toxic heavy metals from wastewater. In this research, the removal efficiency and mechanism of chromium removal by a silica-based nanoparticle were investigated. A PEI-silica nanoparticle was synthesized by a one-pot technique and exhibited uniformly well-dispersed PEI polymers in silica particles. The adsorption capacity of chromium ions was determined by a batch adsorption test, with the PEI-silica nanoparticle having a value of 183.7 mg/g and monolayer sorption. Adsorption of chromium ions was affected by the solution pH and altered the nanoparticle surface chemically. First principles calculations of the adsorption energies for the relevant adsorption configurations and XPS peaks of Cr and N showed that Cr(VI), [HCrO4]- is reduced to two species, Cr(III), CrOH2+ and Cr3+, by an amine group and that Cr(III) and Cr(VI) ions are adsorbed on different functional groups, oxidized N and NH3+.

Investigation of the mechanism of chromium removal in (3-aminopropyl)trimethoxysilane functionalized mesoporous silica.

We are proposed that a possible mechanism for Cr(VI) removal by functionalized mesoporous silica. Mesoporous silica was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) using the post-synthesis grafting method. The synthesized materials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, Fourier-transform infrared (FT-IR), thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS) to confirm the pore structure and functionalization of amine groups, and were subsequently used as adsorbents for the removal of Cr(VI) from aqueous solution. As the concentration of APTMS increases from 0.01 M to 0.25 M, the surface area of mesoporous silica decreases from 857.9 m2/g to 402.6 m2/g. In contrast, Cr(VI) uptake increases from 36.95 mg/g to 83.50 mg/g. This indicates that the enhanced Cr(VI) removal was primarily due to the activity of functional groups. It is thought that the optimum concentration of APTMS for functionalization is approximately 0.05 M. According to XPS data, NH3+ and protonated NH2 from APTMS adsorbed anionic Cr(VI) by electrostatic interaction and changed the solution pH. Equilibrium data are well fitted by Temkin and Sips isotherms. This research shows promising results for the application of amino functionalized mesoporous silica as an adsorbent to removal Cr(VI) from aqueous solution.

Up-conversion luminescence in Yb(3+)-Er(3+)Tm(3+) co-doped Al(2)O(3)-TiO(2) nano-composites.

The sol gel method was used to prepare rare-earths (Yb3+-Er3+ and Yb3+-Tm3+) co-doped Al2O3-TiO2 nano-composite powder phosphors and their up-conversion luminescence properties were investigated. Mixed oxides of titania (TiO2) rutile phase and an early stage crystallization of alumina (Al2O3) phase were confirmed from the X-ray diffraction data with the average crystallite size of ∼36nm. The rutile phase TiO2 was further confirmed by selected area diffraction analysis of the composites. Microscopy analysis showed interesting rod-like morphologies with rough surfaces indicating that a spherulitic growth process took place during the crystal growth. Photoluminescence characterization of the phosphors was carried out under near infra-red excitation at 980nm and the prominent emission bands were observed in the visible region at 523, 548 and 658nm for the Yb3+-Er3+ co-doped systems. Emission in bands extending from the visible to near infra-red regions were observed at 480, 650, 693 and 800nm for the Yb3+-Tm3+ co-doped systems. These upconverted emissions and energy transfer mechanisms taking place are discussed in detail.