Phosphorous Modification Research Articles

Advances in Reversible Luminescence Modification and Applications of Inorganic Phosphors Based on Chromism Reaction

AbstractThe reversible luminescence modification of inorganic phosphors has emerged as a promising field, enabling innovative applications such as optical memory, multiple anti‐counterfeiting, and photoswitches. Traditional luminescence modulation techniques, such as core–shell structure design and energy transfer‐related luminescent ions regulation, face challenges in achieving reversible luminescence modification. Chromism induces reversible color changes in materials when stimulated by external fields such as electricity, heat, and light. Combining chromism with luminescence enables the creation of chromism‐driven reversible luminescence manipulation in a single material. This review summarizes recent advances in reversible luminescence modification of inorganic phosphors based on chromism reaction and highlights their potential applications in optical data storage, fingerprint acquisition, and anti‐counterfeiting areas. The potential prospective research directions are also discussed and the challenges and opportunities of chromism‐based reversible luminescent materials are presented for further extended applications.

Phosphorus promotion on hydrothermal stability of ZSM-5 by P precursors with different molecular sizes

The promotional effects of phosphorous modification on ZSM-5 zeolites by phosphorus oxyacids (H4P2O7, H3PO4, H3PO3, and H3PO2) with different molecular sizes were investigated with catalytic cracking of n-tetradecane as the probe reaction. It was verified that the diffusion of P precursor molecules into ZSM-5 channels was important to prevent aggregation of P species for better stabilization on tetra-coordinated framework aluminum. Meanwhile, the P–Al interaction was proposed based on results of 27Al, 31P, and 29Si MAS NMR. With H3PO2 as the P precursor, easy diffusion into ZSM-5 channels contributed to less formation of polyphosphates, homogeneous distribution of P species, better reserved crystallinity, microporous area and acidic sites for improving cracking performance of n-tetradecane.

Research progress on surface modifications for phosphors used in light-emitting diodes (LEDs).

Stable and efficient phosphors are highly important for light-emitting diodes (LEDs) with respect to their application in solid-state lighting, instead of conventional lamps for general lighting. However, some problems, like low stability, low photoluminescence (PL) efficiency, and serious thermal degradation, are commonly encountered in phosphors, limiting their applications in LEDs. Surface modifications for some phosphors commonly used in LED lighting, including fluoride, sulphide, silicate, oxide, nitride, and oxynitride phosphors, are presented in this review. By forming a protective surface layer, the stabilities against moisture and high temperature of fluoride- and sulphide-based phosphors were strengthened; by coating inorganic and organic materials around the particle surface, the PL efficiencies of silicate- and oxide-based phosphors were improved; by passivation treatment upon the phosphor surface, the thermal degradation of nitride- and oxynitride-based phosphors was reduced. Various technologies for surface modification are described in detail; moreover, the mechanisms of stability strengthening, PL efficiency improvement, and thermal degradation reduction are explained. In addition, embedding of phosphors in inorganic glass matrix, especially for quantum dots, is also introduced as an effective method to improve phosphor stability for LED applications. Finally, future developments of surface modification of phosphors are proposed.

The beneficial effects of black phosphorous modification of the anode current collector in Li-metal free Li2S-based batteries

Li–S batteries assembled without a lithium metal anode can significantly increase the battery specific energy and obviate the safety issue of excess Li metal in the battery. In this study we found that a black phosphorous (BP) modified cooper foil current collector could provide a beneficial anode solid-electrolyte-interface (SEI) to enable the charging and discharging of Li-metal free Li2S-based batteries at higher C rates. The BP modification is effective in several aspects: the lithiophilicity of BP reduces the energy barrier in Li metal deposition and stripping during battery charge and discharge. The reactions between BP and lithium polysulfides also form Li7PS6 in the anode SEI layer. Since Li7PS6 has a high ionic conductivity for Li + diffusion, the Li plating/stripping efficiency is improved. The synergy of the lithiophilicity of BP and a Li7PS6-rich anode interphase layer was demonstrated in Li-metal free Li2S batteries, where the capacity retention over 100 cycles is 64.8% at the 0.2 C rate. The findings here show that current collector modifications should attend to multiple functionalities in order to be effective for the Li-metal free Li2S batteries.

A Highly Stable Bimetallic Transition Metal Phosphide Catalyst for Selective Dehydrogenation of n‐Heptane

AbstractIn this work, we demonstrate RuP2‐MoP catalysts being highly stable and selective for the dehydrogenation of long‐chain alkanes like n‐heptane. Compared to a monometallic MoP catalyst, the bimetallic system substantially increases n‐heptene selectivity from 40 % towards 80 %. This effect can be traced back to a reduced surface acidity, suppressing the competitive hydrogenolysis reaction. The active transition metal phosphide is, furthermore, compared to its phosphorous‐free RuMo‐counterpart. As revealed by STEM‐EDX investigations, incorporation of phosphorous results in the formation of separated metal phosphide clusters instead of an intermetallic alloy. In the dehydrogenation of n‐heptane the phosphorous modification clearly avoids catalyst deactivation and maintains the high n‐heptene selectivity. X‐ray diffraction, elemental analysis and STEM‐EDX further reveal that catalyst coking and the formation of less active molybdenum carbide phases is effectively suppressed by phosphorous incorporation, making RuP2‐MoP an attractive system for selective dehydrogenation of long‐chain alkanes.

Improving Both the Activity and Selectivity of CoMo/δ-Al2O3 by Phosphorous Modification for the Hydrodesulfurization of Fluid Catalytic Cracking Naphtha

Improving Both the Activity and Selectivity of CoMo/δ-Al₂O₃ by Phosphorous Modification for the Hydrodesulfurization of Fluid Catalytic Cracking Naphtha

Simultaneous Spectral Tuning and Thermal Stability Adjustment in Ca8ZnGa(1-x)Lax(PO4)7:Eu2+ Phosphors.

The modifications of local structure in solid solution are a crucial step to regulate the photoluminescence properties of rare-earth ion-based phosphors. However, the structural diversity of host matrices and the uncertain occupation of activators make it challenging to obtain phosphors with both high stability and tailored emission. Herein, We synthesized a series of β-Ca3(PO4)2-type Ca8ZnGa(1-x)Lax(PO4)7:Eu2+ solid solution phosphors by design. By modifying the Ga/La ratio, controllable regulation of the emission spectrum and thermal stability of the phosphors can be achieved at the same time. The introduction of La3+ can regulate the crystal field splitting strength of the Eu2+ activators, causing redshifts in the emission spectrum while increasing Ga3+ content will lead to enhanced energy transfer between the oxygen vacancy and Eu2+, as well as improved thermal stability. Through local structure modification, the spectrum and thermal stability of phosphors can be facilely tuned. The results indicate that this series of phosphors have versatile potentials in various applications.

Silica Nanoparticle Coating of NaYF4:(Yb3+, Er3+) Upconversion Phosphor

To improve its light conversion efficiency, NaYF4:(Yb3+, Er3+) upconversion (UC) phosphor, which generates one visible photon by absorbing two or more near‐infrared photons, was coated with SiO2 nanoparticles. The surface modification of phosphor was performed by using a modified sol–gel method as a function of the concentration of colloidal silica employed as the surface coating precursor. It was found that the PL intensities depend on the concentration of colloidal silica. When a 2.7 wt% concentration of colloidal silica was used, the NaYF4:(Yb3+, Er3+) phosphor exhibited a homogeneous coating with silica and an approximately 9% increase in the PL intensity, as compared with that of the non‐coated sample of NaYF4:(Yb3+, Er3+) phosphor. This increase in the PL intensity can be explained by the suppression of the nonradiative recombination of electron–hole pairs via surface defects. The experimental results suggest that the surface modification of upconversion phosphors with a silica coating of the appropriate concentration is a simple and effective solution to improve the light conversion efficiency of upconversion phosphors used in optoelectronic devices.

Sr2MgSi2O7:Eu2+, Dy3+ phosphor‐reinforced wood plastic composites with photoluminescence properties for 3D printing

AbstractCombining wood plastic composites with 3D printing technology can easily manufacture parts with complex shapes and wood colors, but the single function limits their applications. In this research, Sr2MgSi2O7:Eu2+, Dy3+ phosphors/particleboard wood flour/poly (lactic acid) (SMSED/PWF/PLA) photoluminescence composites for 3D printing were successfully manufactured by melt extrusion. The water resistance and chemical structure of SMSED phosphors modified with five different types of silane coupling agents were characterized by water‐resistance test, Fourier transform infrared spectroscopy, and X‐ray diffraction. It was found that 3‐aminopropyltriethoxysilane (KH550) had the best effect on the modification of SMSED phosphors, formed a dense protective film. Afterward, the effect of KH550‐modified SMSED (KH550‐SMSED) phosphors content on the thermo‐mechanical properties of wood plastic composites was studied. The experimental results indicated that the mechanical properties and thermal stability of wood plastic composites were significantly improved, with the incorporation of KH550‐SMSED phosphors. Finally, based on SMSED/PWF/PLA composites and 3D printing technology, a safety warning model that could emit blue light in the dark and a small dinosaur artwork that could swing flexibly were prepared.

High moisture resistance of an efficient Mn4+-activated red phosphor Cs2NbOF5:Mn4+ for WLEDs

Mn4+-activated fluoride red phosphors, the most important red phosphors for warm white light emitting diodes (LEDs), usually suffer from inherent poor moisture resistance which is a major obstacle to their long-lasting outdoor applications in a high humidity environment. Surface modification of phosphors by coating with either organic or inorganic shells is an effective way to improve waterproof stability. However, the coating procedure usually has a negative impact on the luminous efficacy due to the increased passivation shell thickness. In this work, Mn4+-activated oxyfluoroniobate (Cs2NbOF5), a highly efficient phosphor with internal quantum efficiency of ca. 82%, has been successfully synthesized and it is interesting to note that Cs2NbOF5:Mn4+ can exhibit remarkably improved waterproof stability even without surface coating compared to well-accepted commercial fluoride red-emitting phosphor, K2SiF6:Mn4+. The results obtained indicate that Nb5+ ions inside red phosphor play a crucial role in improving the water-resistant performance of Mn4+, which provides a new concept for overcoming the downside of their waterproof in humid conditions and maintaining the luminescence efficiency. In the final phase white LEDs with a high luminous efficacy of 174 lm/W (higher than commercial fluoride red phosphors), low correlated color temperature (3164 K) and high color rendering index (Ra = 90 and R9 = 85) have been fabricated using Cs2NbOF5:Mn4+.

Improved performance of mesoporous HZSM-5 designed with selective deactivation of external surface acidity in the isomerization of styrene oxide

Abstract A series of mesoporous HZSM-5 designed by phosphorous modification with or without hexadecyltrimethylammonium bromide (CTAB) pretreatment were prepared and tested in the isomerization of styrene oxide. CTAB pretreatment changed the external surface properties of mesoporous HZSM-5 with positive charged, which could selectively adsorb the phosphate anions and deactivate the external Bronsted acid sites caused by a framework dealumination during calcinations. The phosphate species on the external surface could not migrate into the micropores. There were only a few phosphate species formed in the micropores and most of the internal Bronsted acid sites were preserved. External surface deactivation whilst retaining the hierarchical pore structure of mesoporous HZSM-5 was achieved by phosphorous modification with CTAB pretreatment, thus providing a potential industrial application catalyst which remarkably improves the catalytic stability (lifetime 59.8 h) while preserving the high activity (>99%) and selectivity (>96%).

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)5(PO4)3Br and the Defect Process.

Intrinsic defect-related luminescence has recently been attracting more research interest for the modification of phosphors. However, the connection between defect formation and crystal structure has never been considered. In this work, we report that in the absence of an impurity activator, under a reducing atmosphere, apatite-type compound M5(PO4)3X (M = Ca, Sr, or Ba; X = F, Cl, or Br) can emit tunable colors ranging from blue to orange depending on the content of M and X. To better understand the cause, Ba5- mSr m(PO4)3Br (BSPOB; m = 0-5) solid solutions were analyzed in detail. The dependency of self-activated luminescence on atmospheric conditions and solid solution compositions was investigated by combining experimental characterizations and theoretical calculations using density functional theory. Crystal structures of these solid solutions were verified by X-ray diffraction patterns as well as Rietveld refinements. With the defect formation energy and electron paramagnetic resonance measurement, we propose that an oxygen vacancy (VO) should be mainly responsible for the peculiar super wide band emission. Moreover, the enhanced distortion of solid solution crystal structures augments VO concentrations and leads to luminescence intensities in solid solutions that are higher than that in end point compounds. Variations of the electronic structure of BSPOB matrices with gradual tuning of the Sr/Ba ratio were also investigated. As a result, the introduction of VO defect levels within the band gap leads to the formation of donors and acceptors, allowing for a modulation of the photoluminescence throughout the visible part of the spectrum. As the first report in the literature to demonstrate fine-tunable emissions over a wide wavelength range as a consequence of native defective levels in a series of continuous apatite-type solid solutions, our results illustrate the feasibility of defect-meditated systems by carefully tailoring defect chemistry and nonstoichiometric chemical composition under controlled conditions to engineer phosphor properties.

Effect of framework single and close (pairs and un-pairs) aluminum atoms on phosphorous modification of HZSM-5 in cracking of liquefied petroleum gas to ethylene and propylene

To investigate the effects of framework single and close Al atoms on modification of HZSM-5 with phosphorus and steam in liquefied petroleum gas (LPG) cracking to light olefins, HZSM-5 zeolites were synthesized with two Al sources including Al(NO3)3 and Al(OH)3. The unmodified, P-modified HZSM-5 and steam-treated P/HZSM-5 zeolites were characterized by XRD, BET, 27Al MAS NMR and NH3-TPD techniques. The Al locations in the HZSM-5 zeolites were determined by combining the results of XRF and diffuse reflectance UV–visible spectroscopy. The catalytic performance showed that the olefin yields and catalytic stability of HZSM-5(1) synthesized with higher single Al atoms and lower Al atoms at channel intersections (β sites) was greater than that of HZSM-5(2) synthesized with higher close and pair Al atoms. The reduction of acid site strength and increment of weak to strong (W/S) acid ratio after P modifications and steam treatment resulted in a significant increase of olefin yields and a decrease of C5+ yields and coke amount. The catalytic stability and propylene to ethylene (P/E) ratio for P/HZSM-5(1) with lower strong acid sites was greater than that of P/HZSM-5(2). The P/E ratio, deactivation rate, propylene yield and olefin yields were found to be 1.005, 13.58%, 23.42% and 46.72% for P/St/HZSM-5(1) and 0.959, 15.49%, 20.09% and 41.04% for P/St/HZSM-5(1) after 240 min. The catalytic results showed that the highest and lowest catalytic stability were related to the P/St/HZSM-5(1) and HZSM-5(2) catalysts, respectively.

One-step post-synthesis treatment for preparing hydrothermally stable hierarchically porous ZSM-5

Hierarchically porous ZSM-5 (SiO2/Al2O3 ≈ 120) containing phosphorus was prepared by a one-step post-synthesis treatment involving controlled desilication and phosphorous modification. The hierarchically porous ZSM-5 featured high thermal and hydrothermal stability. The obtained ZSM-5 zeolites were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption, NH3 temperature-programmed desorption, and 27Al and 31P magic-angle spinning nuclear magnetic resonance spectroscopy. The prepared ZSM-5 displayed enhanced activity and prolonged lifetime toward hydrocarbon cracking. The high activity was attributed to improved coke tolerance owing to the presence of the highly stable mesoporous network of ZSM-5 and acid sites introduced upon phosphorus modification. Additionally a mechanism of the stabilization of the zeolites by phosphorus was proposed and discussed.

A colloidal quantum dot photonic crystal phosphor: nanostructural engineering of the phosphor for enhanced color conversion.

Phosphors, long-known color-converting photonic agents, are gaining increasing attention owing to the interest in white LEDs and related applications. Conventional material-based approaches to phosphors focus on obtaining the desired absorption/emission wavelengths and/or improving quantum efficiency. Here, we report a novel approach for enhancing the performance of phosphors: structural modification of phosphors. We incorporated inorganic colloidal quantum dots (CQDs) into a lateral one-dimensional (1D) photonic crystal (PhC) thin-film structure, with its photonic band-edge (PBE) modes matching the energy of 'excitation photons' (rather than 'emitted photons', as in most other PBE application devices). At resonance, we observed an approximately 4-fold enhancement of fluorescence over the reference bulk phosphor, which reflects an improved absorption of the excitation photons. This nano-structural engineering approach is a paradigm shift in the phosphor research area and may help to develop next-generation higher efficiency phosphors with novel characteristics.

Roles of phosphorous-modified Al2O3 for an enhanced stability of Co/Al2O3 for CO hydrogenation to hydrocarbons

A phosphorous-modified γ-Al2O3 (P-Al2O3), where γ-Al2O3 support was prepared by sol-gel method with a high surface area of ∼350m2/g, has been applied for a preparation of cobalt-supported Co/P-Al2O3 catalysts. The Co/P-Al2O3 catalysts having a different P/Al molar ratio were investigated to elucidate the roles of phosphorous species on the γ-Al2O3 to the catalytic stability and product distribution for CO hydrogenation to hydrocarbons. The γ-Al2O3 surface was partially transformed to aluminum phosphates after phosphorous modification, and the newly formed aluminum phosphate phases simultaneously altered the surface hydrophilicity and cobalt dispersion as well. The partial formation of tridymite aluminum phosphate (AlPO4) phases on the P-Al2O3 support eventually enhanced the dispersion of the supported cobalt crystallites and suppressed the aggregation of cobalt nanoparticles by forming the strongly interacted cobalt crystallites on the P-Al2O3 surfaces. The phosphorous-modified Fischer-Tropsch synthesis (FTS) catalyst also significantly suppressed heavy hydrocarbon depositions due to an increased surface hydrophilicity originated from partially formed SiO2-like tridymite AlPO4 surfaces. A higher stability of the Co/P-Al2O3 catalyst at an optimal phosphorous content in the range of 0.5–1.0 mol% was attributed to homogeneously distributed cobalt crystallites and less deposition of heavy hydrocarbons by forming macro-emulsion droplets with the help of trace amount of alcohols formed during FTS reaction. This was confirmed by in-situ analysis of adsorbed intermediates with surface hydrophilicity and some surface characterizations such as crystallite size, reducibility, and electronic state of the supported cobalt nanoparticles.

Remarkably enhanced stability of HZSM-5 zeolite co-modified with alkaline and phosphorous for the selective conversion of bio-ethanol to propylene

The effects of alkaline, phosphorous and dual alkaline-phosphorous modifications on the selective conversion of bio-ethanol to propylene over HZSM-5 zeolite catalysts were investigated. The results demonstrate that the doubly modified HZSM-5 zeolite catalyst offers higher propylene selectivity and remarkably improved catalytic stability than the parent and singly modified counterparts, which can be contributed to the formation of new mesoporous and decreased amount of strong acid sites induced by the alkaline treatment and phosphorous modification, respectively. The deactivation of the phosphorous and dual alkaline-phosphorous modified HZSM-5 zeolite catalysts was caused by carbon deposition but not by dealumination, which can be attributed to the enhanced hydrothermal stability of the framework aluminum by the modification of ZSM-5 zeolite with phosphorus.

A facile strategy for preparation of phosphorus modified HZSM-5 shape-selective catalysts and its performances in disproportionation of toluene

The phosphorous modified HZSM-5 catalysts were prepared by using phosphoric acid as the precursor with the addition of ethanol during the impregnation process and their shape-selective performances in the synthesis of p-xylene by disproportionation of toluene were investigated. An excellent para-selectivity along with a relatively high catalytic activity was achieved over the phosphorous modified HZSM-5 catalysts. The addition of ethanol during the impregnation process promotes the transition of phosphoric acid to phosphate, which accomplished the cover of the external acid sites and the reserve of the acid sites in the pores of HZSM-5 zeolite after phosphorous modification.

Synthesis of phosphorus-modified small-pore zeolites utilizing tetraalkyl phosphonium cations as both structure-directing and phosphorous modification agents

A rational strategy for the synthesis of phosphorus-modified small-pore zeolites by utilizing tetraalkyl phosphonium cations as both a structure-directing agent and a phosphorous modification agent was developed. Initially, we investigated the hydrothermal conversion of FAU zeolites as a starting silica/alumina source in the presence of tetraalkyl phosphonium cations with different structures. Various types of zeolites, including small-pore zeolites with 8-MR windows such as LEV, GIS, AEI, and CHA zeolites, were obtained. Next, we applied the dual-template method with a mixture of the N-containing organic structure-directing agent (OSDA) N,N,N-trimethyl-1-adamantammonium cation and the P-containing OSDA tetraethyl phosphonium cation to the synthesis of phosphorus-modified zeolites with small pores, especially CHA zeolites. Using this method, the proportion of P-containing OSDA/N-containing OSDA in as-synthesized CHA zeolites can be easily controlled. After the calcination of the as-synthesized zeolites, CHA zeolites with different degrees of phosphorus modification were easily obtained without significant pore occlusion or toxification of catalytically active sites. The phosphorus-modified CHA zeolite had high thermal stability and retained its structure even after calcination at 1050 °C for 1 h. In addition, in the selective catalytic reduction of NOx with NH3, the Cu-loaded phosphorus-modified CHA zeolite exhibited NO conversion above 90%, even after hydrothermal treatment at 900 °C for 8 h, indicating extremely high hydrothermal stability.

Active intermediates formed on phosphorous-modified MTW zeolites in methanol to olefin conversion: An ESR study

The active intermediates formed on phosphorous-modified MTW zeolites in methanol-to-olefin (MTO) were investigated using electron spin resonance (ESR) spectroscopy. The porous and acidic properties of the modified catalysts were characterized by XRD, SEM, N2 adsorption, o-xylene uptake, and temperature-programmed desorption of ammonia. In addition to the repeated potential restrictions to adsorbed aromatic compounds in its 12 membered-ring, the phosphorous modification on MTW zeolites reduces the number of strong acid sites and limits the close distribution of polymethylbenzenes formed during MTO conversion, facilitating the observation of ESR signals with hyperfine splittings of hexamethylbenzenium radical cations, while the poor resolution of the hyperfine splittings supposed the co-presence of other radical cations. The positive relationship between the conversion of methanol and the spin number of radical cations over the MTW catalysts at the early stage confirms the role of these radical cations as actual active intermediates. The high methyl group substitution of the active intermediate formed on MTW catalysts is responsible for the high yields to C3C6 (above 90%) at 450°C in MTO conversion.