Cr Nanoparticles Research Articles

Metal-organic framework-edaravone nanoparticles for radiotherapy-induced brain injury treatment

Cranial radiotherapy may cause damage to normal brain tissues and induce cognitive dysfunction, so developing an effective strategy to prevent radiotherapy-induced brain injury is essential. Metal-organic frameworks (MOFs) can be used as vectors for the delivery of neuroprotective drugs due to their high drug loading capacity and low toxicity. In this study, we synthesized MIL-53(Cr) nanoparticles, which were used to deliver edaravone, and modified the surface of the nanoparticles with polyethylene glycol and Angiopep-2 (EDA@MIL-53(Cr)–P/A) to improve their oral bioavailability and ability to cross the blood–brain barrier (BBB). We confirmed that MIL-53(Cr)–P/A nanoparticles could achieve the sustained release of edaravone and enhance its ability to cross the BBB. The results of in vitro experiments showed that EDA@MIL-53(Cr)–P/A could exert radioprotective effects on HT22 and BV2 cells. We also demonstrated that EDA@MIL-53(Cr)–P/A could alleviate brain injury and cognitive dysfunction in mice receiving whole-brain irradiation. Mechanistically, EDA@MIL-53(Cr)–P/A alleviated irradiation-induced brain damage by inhibiting oxidative stress, DNA damage, apoptosis and inflammatory reactions. This study provides a new strategy for the protection against radiotherapy-induced brain injury.

The detection of acetone in exhaled breath using gas Pre-Concentrator by modified Metal-Organic framework nanoparticles

Volatile organic compounds (VOCs) from exhaled breath are promising indicators for the diagnostics of human health conditions. However, the composition of breath is rather complex, including water vapors and various tiny amounts of gases and biomarkers. Pre-concentrator plays a significant role in capturing and concentrating target gas in the gas mixture. In this work, the MIL-101 (Cr) nanoparticles are coated with polydimethylsiloxane (PDMS) through physical vapor deposition process to concentrate acetone under high humidity and room temperature. Experimentally, the newly developed material exhibits significant improvement in signal intensity that is 76.3 times greater than a commercial reference material under relative humility of 80 %. The detection range is also proven to be desirable (from 100 ppb to 2500 ppb), capturing the spectrum of acetone concentrations typically found in human exhaled breath. Moreover, following a thermal desorption process, the device demonstrates a high degree of linearity with a coefficient of 0.9956. The modified metal–organic framework materials are made into a flexible thin-film-shape device, that could be embedded in a facemask. The proposed device could meet the critical requirements for sampling, concentrating and detecting of exhaled breath biomarkers, thereby opening a new opportunity as part of the flexible electronic systems on face masks to facilitate quantitative breath analyses.

Electric-field assisted spatioselective deposition of MIL-101(Cr)PEDOT to enhance electrical conductivity and humidity sensing performance

Precise deposition of metal–organic framework (MOF) materials is important for fabricating high-performing MOF-based devices. Electric-field assisted drop-casting of poly(3,4-ethylenedioxythiophene)-functionalized (PEDOT) MIL-101(Cr) nanoparticles onto interdigitated electrodes allowed their precise spatioselective deposition as percolating nanoparticle chains in the interelectrode gaps. The resulting aligned materials were investigated for resistive and capacitive humidity sensing and compared with unaligned samples prepared via regular drop-casting. The spatioselective deposition of MOFs resulted in up to over 500 times improved conductivity and approximately 6 times increased responsivity during resistive humidity sensing. The aligned samples also showed good capacitive humidity sensing performance, with up to 310 times capacitance gain at 10 versus 90 % relative humidity. In contrast, the resistive behavior of the unaligned samples rendered them unsuitable for capacitive sensing. This work demonstrates that applying an alternating potential during drop-casting is a simple yet effective method to control MOF deposition for greater efficiency, conductivity, and enhanced humidity sensing performance.

Modification of contact lenses via metal‐organic frameworks for glaucoma treatment

AbstractThe prevention of blindness from glaucoma requires multiple treatments to lower intraocular pressure. Here, human contact lenses are modified with highly porous metal‐organic frameworks with sustained release of brimonidine for prolonged glaucoma treatment. Various metal‐organic frameworks were screened for their attachment to lenses, loading with brimonidine, and drug‐release properties. Optimized therapeutic ocular lenses conjugated with MIL‐101(Cr) frameworks maintain optical transparency and power. Coating of lenses with MIL‐101(Cr) nanoparticles reduced brimonidine washout with tears and ensured a gradual and localized release of the drug into the eyeball through the cornea. The hybrid lenses provided a 4.5‐fold better decrease in eye pressure, compared by area under the curve (AUC) value to a commercially available brimonidine tartrate solution. Therapeutic lenses did not induce any notable eye irritation or corneal damage in vivo. The newly developed hybrid lenses are expected to provide a robust platform for the therapy and prevention of various ocular diseases.

Chromium-doped zinc gallate: Impact of Sn4+ co-doping on the persistent luminescence properties at the nanoscale applied to bio-imaging

Persistent luminescence (PersL) nanoparticles emit a signal that lasts long after the excitation has ended, enabling highly sensitive bioimaging without background noise. By using UV light as the excitation source prior to injection, a strong PersL signal can be detected in vivo before disappearing within a few hours. For long-term imaging, we have shown in the past that visible LED can be used to re-excite ZnGa1.995Cr0.005O4 (ZGO:Cr3+) nanoparticles in vivo, producing a signal intensity that is, however, much lower compared to the signal obtained after the UV pre-excitation method. This lower signal intensity of the nanoprobe when using a visible LED may prevent its detection in some cases. Herein, we report an improvement in visible LED excitation efficiency using PersL Zn1.33Ga1.335Cr0.005Sn0.33O4 (ZGSO:Cr3+) nanoparticles. We fully compared ZGSO:Cr3+ and the original ZGO:Cr nanoparticles in terms of structure, optical properties and bio-imaging potential. Co-doping with tin strongly increases persistent luminescence, even at the nanoscale. In vivo imaging results showed that ZGSO:Cr3+ exhibited an approximately 3-fold signal enhancement over ZGO:Cr3+ using UV pre-excitation. More interestingly, when using LED excitation, the signal intensity of ZGSO: Cr3+ is more than 10 times higher than that of ZGO:Cr3+, making ZGSO nanoparticles much easier to detect. ZGSO:Cr nanoparticles can be surface-modified with PEG to produce nanoprobes with much longer residence time in blood. This unique comparison between the two compositions makes ZGSO:Cr3+ a more effective imaging diagnostic probe than the original ZGO:Cr3+ nanoparticles, opening up new applications for in vivo diagnostics.

Ionic Cross-Linked MOF-Polymer Mixed-Matrix Membranes for Suppressing Interfacial Defects and Plasticization Behavior.

To address the plasticization phenomenon and MOF-polymer interfacial defects, we report the synthesis of ionic cross-linked MOF MMMs from a dual brominated polymer and MOF components by using N,N'-dimethylpiperazine as the cross-linker. We synthesized brominated MIL-101(Cr) nanoparticles by using mixed linkers and prepared brominated polyimide (6FDA-DAM-Br) to form ionic cross-linked MMMs. The gas permeation properties of the polyimide, ionic cross-linked MOF-polymer MMMs, and non-cross-linked MOF-polymer MMMs with various MOF weight loadings were investigated systematically to effectively understand the effects of MOF weight loading and ionic cross-linking. The ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly enhanced gas permeability with an H2 permeability of 1640 Barrer and CO2 permeability of 1981 Barrer and slightly decreased H2/CH4, H2/N2, CO2/CH4 and CO2/N2 selectivities of 16.9, 15.4, 20.5, and 18.6, respectively. The H2 and CO2 permeabilities are approximately 2-3 fold higher than those of the pure polyimide (6FDA-DAM) membrane. Moreover, the ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly increased resistance to plasticization. This is because the brominated MOF incorporation boosted molecular transport and polymer chain rigidity, and ionic cross-linking further reduced the number of interfacial defects and polymer chain mobility.

Enhanced precipitation hardening in nanograined CuCrZr alloy

Nanograins were induced in solid solution CuCrZr alloy by surface mechanical grinding treatment, followed by aging treatment to investigate the precipitation behavior and hardening effect of the nanograins. Experimental results showed that body-centered cubic Cr nanoparticles precipitated at nanograin boundaries accompanied with slight nanograin coarsening, yielding a considerable precipitation hardening, even twice that of coarse grains. The hardening mechanism of grain boundary nanoprecipitates in nanograins was discussed.

Optimal adsorption of pefloxacin antibiotics from aqueous solutions: Improved performance with metal-organic framework MIL-101(Cr)

The widespread use and subsequent release of antibiotics by humans and animals pose health and environmental risks, compelling their removal from aquatic ecosystems. MIL-101(Cr), a metal-organic framework (MOF), exhibits versatile applications in antibiotic adsorption owing to its exceptional structural characteristics. In this context, MIL-101(Cr) nanoparticles are successfully prepared via the hydrothermal method to remove pefloxacin (PEF) from aqueous solutions. The resulting MIL-101(Cr) adsorbents showcase high crystallinity (97.6%), a large surface area (3166 m2/g), broad nanopore sizes, good thermal stability, and efficient reusability. Factors including initial PEF concentration, pH, dosage of adsorbent, and temperature are thoroughly investigated. The findings reveal a good adsorption capacity (254.3 mg/g) with an optimal removal efficiency (99.7%) at 308 K in a neutral pH of 7.0 when the adsorbent dosage is 250 mg/L and the initial PEF concentration is 200 mg/L within 80 min of contact. Among the three adsorption isotherms (Langmuir, Freundlich, Temkin models), the Langmuir equation best fits the studies, indicating a maximum adsorption capacity of 253.8 mg/g at 25°C, while the experimental equilibrium adsorption capacity is 229.2 mg/g at the same temperature. Adsorption kinetics aligns with the pseudo-second-order model. Thermodynamic parameters and activation energy affirm the endothermic and spontaneous behavior of the adsorption process, attributed to both physisorption and chemisorption. This study highlights the promising potential of synthesized MOF nanocrystals as an effective adsorbent for antibiotics in wastewater treatment and environmental remediation.

Optimizing the Performance of a Pd Film-Based Room-Temperature H2 Sensor by Eliminating the Clamping Effect with Cr Nanoparticles

Optimizing the Performance of a Pd Film-Based Room-Temperature H₂ Sensor by Eliminating the Clamping Effect with Cr Nanoparticles

Electrochemical Properties of LaMO3(M=Cr, Mn, and Co) Perovskite Materials

The utilization of lanthanide perovskite oxides as electrode materials for supercapacitors has garnered significant interest owing to their excellent electrical conductivity, low cost, and excellent thermal stability. In this study, LaMO3(M=Cr, Mn, and Co) nanoparticles were prepared by the sol–gel method coupled with a calcination process. To evaluate the microstructures, morphologies, and electrochemical properties of the samples, a variety of techniques were employed, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) cycling, and electrochemical impedance spectroscopy (EIS). The results revealed that the LaCoO3 electrodes exhibited a maximum specific capacitance of 118.4 F/g at a current density of 1 A/g, attributed to its higher concentration of oxygen vacancy, larger specific surface area, and lower charge transfer resistance. This discovery substantiates the notion that the electrochemical efficacy is enhanced with the diminishing B-site cation radius in the perovskite LaMO3 system. The charge–discharge process was employed to investigate the anion-intercalation mechanism of LaMO3(M=Cr, Mn, and Co).

Highly efficient persistent luminescent nanozymes-based luminescence-colorimetric dual-mode sensor for total antioxidant capacity assay

Total antioxidant capacity (TAC) is a vital parameter to assess the gross antioxidant activity in biological and food matrices. Accurate determination of TAC has become increasingly important for health monitoring and dietary guidance. Here, we report a persistent luminescent nanozyme (ZGO-Pt) based luminescence-colorimetric dual-mode sensor for selective determination of TAC. ZGO-Pt was fabricated based on ZnGa2O4:Cr nanoparticles (ZGO) with platinum nanoflower as synthetic additive. The prepared ZGO-Pt exhibited fascinating peroxidase-mimetic activity and persistent luminescence, and enabled effectively catalysis of the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB. Meanwhile, the generated oxTMB gave strong absorption at 652 nm to quench the luminescence of ZGO-Pt at 700 nm via the inner filter effect. Antioxidants could compete with the oxidable TMB or reduce oxTMB to TMB, resulting in the simultaneous variations of blue color and luminescence to provide the basis for dual-mode assay for TAC. The highly efficient catalysis of ZGO-Pt (Km, 3.12 mM for H2O2, 0.592 mM for TMB) allows the dual-mode sensor to realize precise determination of TAC with a wide linear range (0.5–200 μM and 1–300 μM for colorimetric and luminescence mode, respectively) and low limit of detection (LOD, 0.05 μM and 0.78 μM for colorimetric and luminescence mode, respectively). The developed dual-mode sensor was successfully applied to the determination of TAC in vitamin tablet, beverages and fruits. This work provides an efficient persistent luminescent nanoparticle-based nanozyme for a facile TAC assay with further vision in biosensing and food technology.

Lighting up endogenous H2O2 in the tumor microenvironment using a dual-mode nanoprobe for long afterglow and MR bioimaging.

Persistent luminescent nanoparticles (PLNPs) are excellent luminescent materials, and near-infrared PLNPs are efficiently applied for biosensing and bioimaging due to their advantages of no excitation, excellent light stability and long afterglow. However, due to interference from the complex environment within organisms, single-mode imaging methods often face limitations in selectivity, sensitivity, and accuracy. Therefore, it is desirable to construct a dual-mode imaging probe strategy with higher specificity and sensitivity for bioimaging. Magnetic resonance imaging (MRI) has been widely used in the field of bioimaging due to its advantages of high resolution, non-radiation and non-invasiveness. Here, by combining near-infrared PLNPs and manganese dioxide (MnO2) nanosheets, a sensitive and convenient dual-mode "turn on" bioimaging nanoprobe ZGC@MnO2 has been developed for long afterglow imaging and MRI of endogenous hydrogen peroxide (H2O2) in the tumor microenvironment (TME). The monitoring of H2O2 has garnered significant attention due to its crucial role in human pathologies. For the dual-mode "turn on" bioimaging nanoprobe, the near-infrared PLNPs of quasi-spherical ZnGa2O4:Cr (ZGC) nanoparticles were synthesized as luminophores, and MnO2 nanosheets were utilized as a fluorescence quencher, carrier and H2O2 recognizer. H2O2 in the TME could reduce MnO2 nanosheets to Mn2+ for MRI, and ZGC nanoparticles were released for long afterglow imaging. Finally, the ZGC@MnO2 nanoprobe exhibited a rapid response, an excellent signal-to-noise ratio and a limit of detection of 3.67 nM for endogenous H2O2 in the TME. This dual-mode approach enhances the detection sensitivity for endogenous H2O2, thereby facilitating the research of endogenous H2O2-associated diseases and clinical diagnostics.

A novel epoxy adhesive with metal organic framework (MOF) and poly(butyl acrylate‐block‐styrene) for bonding aluminum–aluminum joints: A complete overview of mechanical, thermal, and morphological properties

AbstractIn this study, MIL‐101 (Cr) and NH2‐MIL‐101 (Cr) nanoparticles were synthesized by hydrothermal method. Butyl acrylate‐styrene copolymer was used along with these nanoparticles to improve the mechanical properties of epoxy adhesive. The results of the Fourier Transform Infrared (FTIR) and X‐ray diffraction (XRD) test showed that the synthesis and functionalization of the metal organic framework (MOFs) were successful. The mechanical properties and adhesion features in the lap joint bonding of aluminum foil to the aluminum foil of modified epoxy adhesives were investigated by tensile and lap shear tests. The results of the tensile test showed that by adding 0.3 wt% of NH2‐MIL‐101 (Cr) and 2.5 wt% of poly(butyl acrylate‐block‐styrene) to epoxy adhesive, the tensile strength, modulus and toughness of dumbbell samples were increased up to 34.46%, 31.74% and 58.53%, respectively. Furthermore, based on the lap shear test results, by adding 0.3 wt% NH2‐MIL‐101 (Cr) along with 2.5% poly(butyl acrylate‐block‐styrene) to the epoxy adhesive, the lap shear strength of samples increased from 1.05 ± 0.08 MPa to 5.25 ± 0.06 MPa compared to the neat epoxy adhesive. According to the TGA test, the highest thermal stability is related to the sample containing 0.3 wt% of NH2‐MIL‐101 nanoparticles and 2.5 wt% of the copolymer. The image of the fracture surface of the sample containing 0.3 wt%. NH2‐MIL‐101 (Cr) and 2.5 wt% block copolymer shows that the interface of nanoparticles and the matrix improved due to the chemical reaction of functional groups of nanoparticles and adhesive matrix.

Efficient separation of Li+/Mg2+ via positively charged TFN membrane based on the PEI interlayer

Nanofiltration (NF) technology has exceptional mono/divalent ion separation performance, providing considerable application potential for lithium extraction. However, polymeric NF membranes provided only restricted amounts of practical applications since of their low permeability and limited selectivity. Herein, a positively charged membrane designed for Li+/Mg2+ separation was developed, this achievement was accomplished by incorporating NH2-MIL-101(Cr) nanoparticles (NPs) into the polyamide (PA) layer situated atop the polyethyleneimine (PEI) interlayer. The PEI interlayer controlled the amine monomer distribution, regulated the PA nanofilm morphology, and improved the membrane positively charged properties. Meanwhile, the NH2-MIL-101(Cr) could provide Li+ with fast transport paths to further enhance the membrane Li+/Mg2+ separation capability. The improved membrane possessed MgCl2 rejection of 96.1 %, LiCl rejection of 42.3 %, and Li+/Mg2+ separation factor of 102 with outstanding permeance of 17.0 L m-2h−1 bar−1. This research made a valuable contribution to applying NF membranes in lithium extraction processes.

Elucidating growth and biochemical characteristics of rice seedlings under stress from chromium VI salt and nanoparticles.

Plants are usually provoked by a variety of heavy metal (HM) stressors that have adverse effects on their growth and other biochemical characterizations. Among the HMs, chromium has been considered the most toxic for both plants and animals. The present study was conducted to compare the phytotoxic effects of increasing chromium (VI) salt and nanoparticles (NPs) concentrations on various growth indexes of rice (Oryza sativa L. var. swat 1) seedlings grown in a hydroponic system. The 7-day rice seedlings were exposed to Cr (VI) salt and NPs hydroponic suspensions which were adjusted to the concentration of 0, 50, 100, 150, 200 and 250 mg/L. Both the Cr (VI) salt and NPs with lower concentrations (up to 100mg/L) exerted minimum inhibitory effects on the growth performance of rice seedlings. However, a significant decrease in shoot and root length and their fresh and dry weight was recorded at higher doses of Cr (VI) salt (200 mg/L) and NPs (250 mg/L). The stress induced by Cr (VI) salt has drastically affected the roots, whereas, Cr (VI) NPs significantly affected the shoot tissues. Photosynthetic pigments decreased significantly in a dose-dependent manner, and the reduction was more pronounced in rice seedlings exposed to Cr (VI) NPs compared to Cr (VI) salt. Cr (VI) NPs enhanced the membrane permeability in shoots and roots as compared to that of Cr (VI) salt, which resulted in higher concentration of reactive oxygen species (ROS) and increased lipid peroxidation. The activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) increased significantly in shoot/root tissue following exposure to higher doses of Cr (VI) salt (200 mg/L) and NPs stress (250 mg/L), while minor changes in CAT and APX activities were observed in root and shoot tissues after exposure to higher concentration of Cr (VI) NP. Furthermore, the increasing concentrations of Cr (VI) NPs increased the length of stomatal guard cells. Conclusively, Cr (VI) salt and NPs in higher concentrations have higher potential to damage the growth and induce oxidative stress in rice plants.

Single-Particle ICP-MS/MS Application for Routine Screening of Nanoparticles Present in Powder-Based Facial Cosmetics.

The short- and long-term impacts of nanoparticles (NPs) in consumer products are not fully understood. Current European Union (EU) regulations enforce transparency on products containing NPs in cosmetic formulations; however, those set by the U.S. Food and Drug Administration are lacking. This study demonstrates the potential of single-particle inductively coupled plasma tandem mass spectrometry (spICP-MS/MS) as a screening method for NPs present in powder-based facial cosmetics (herein referred to as FCs). A proposed spICP-MS/MS method is presented along with recommended criteria to confirm particle presence and particle detection thresholds in seven FCs. FC products of varying colors, market values, and applications were analyzed for the presence of Bi, Cr, Mg, Mn, Pb, Sn, Ag, Al, and Zn NPs based on their ingredient lists as well as those commonly used in cosmetic formulations. The presence of NPs smaller than 100 nm was observed in all FC samples, and no correlations with their presence and market value were observed. Here, we report qualitative and semi-quantitative results for seven FC samples ranging in color, brand, and shimmer.

Chromium Metal Nanoparticles, Their Reactivity and Reactions

AbstractZerovalent chromium nanoparticles (2.2±0.2 nm in size) are prepared in the liquid phase (THF) by reduction of CrCl2 with lithium naphthalenide ([LiNaph]). The deep black Cr(0) nanoparticle suspensions in THF are colloidally and chemically highly stable. On the other hand, the Cr(0) nanoparticles are highly reactive, e. g., when in contact to O2, H2O, or other oxidizing agents. To probe the reactivity of the Cr(0) nanoparticles in the liquid phase near room temperature (50–80 °C), they are reacted with different coordinatively demanding, N−H, S−H or O−H acidic reactants. This includes the amines 2,2′‐dipyridylamine (HDPA), 2‐(1H‐imidazol‐2‐yl)pyridine (HImPy) and carbazole (HCbz), the thiol 2‐mercaptopyridine (HMPy), and benzoic acid (HBz) as a carboxylate. As a result, the five novel compounds [Cr(DPA)3], [Cr(ImPy)3] ⋅ HImPy, [Cr(MPy)3] ⋅ 0.5 Tol (Tol: toluene), [Na2Cr(Cbz)4(THF)3], and [Cr2(Bz)4(THF)2] are obtained. [Cr(DPA)3] and [Cr(ImPy)3] ⋅ HImPy show Cr(III) coordinated by nitrogen only; [Cr(MPy)3] ⋅ 0.5 Tol shows a coordination of Cr(III) by both N and S atoms. [Na2Cr(Cbz)4(THF)3] and [Cr2(Bz)4(THF)2] contain Cr(II) and exhibit an infinite chain‐like structure and pairs of chromium atoms with fourfold binding.

Novel strategies for the enhancement of the NIR emission in the Ca doped ZnO system: Doping with Cr or adding Sb2S3

We report two novel strategies to enhance the NIR emission in the ZnO:Ca system. In the first strategy, we synthesized ZnO:Ca nanoparticles using a wet chemical method and doped them with various concentration of Cr. SEM images showed that the ZnO:Ca,Cr nanoparticles had a grain-like morphology and their sizes increased from 33 to 110 nm after incrementing the Cr concentration from 4 to 17 mol%. The analysis by X-ray diffraction (XRD) revealed that he ZnO:Ca,Cr sample made with 4 mol% of Cr had a pure hexagonal phase but the other samples synthesized with Cr concentration above 11 mol% presented the hexagonal phase and a small content of Cr2O3 (<3%). Moreover, the photoluminescence (PL) spectra of these samples showed two main emission peaks in the blue and NIR regions (λexc = 265 and 365 nm). In particular, the ZnO:Ca,Cr sample made with 17 mol% of Cr had the strongest NIR emission in the 700–850 nm region and only this sample showed a prominent NIR emission peak at 805 nm. Moreover, the CIE maps showed that the emissions of the ZnO:Ca,Cr samples are located in the blue region under excitation at 265 nm, but it was tuned to the orange region under excitation at 365 nm. In the second strategy, different amounts of Sb2S3 was added during the synthesis of ZnO:Ca to form ZnO:Ca/Sb2S3 composites. In this case, we obtained different morphologies of grains, rod-like and sheet-like for Sb2S3 contents of 10, 28 and 34 wt%, respectively. In addition, the composites presented a mixture of hexagonal and orthorhombic phases, which corresponded to the ZnO and Sb2S3, respectively. The ZnO:Ca/Sb2S3 composites had NIR emissions peaks in the 650–800 nm region and their intensity increased with the content of Sb2S3. Furthermore, their visible emission was tuned from blue to orange-red or to cold white light according to the CIE maps. Overall, the best ZnO:Ca,Cr sample had 312% and 37% higher emission than the ZnO:Ca reference sample and the best ZnO:Ca/Sb2S3 composite (under 265 nm excitation), respectively. In general, XPS studies showed the existence of oxygen vacancy defects, which produced the visible-NIR emissions in all the samples. The strategies presented here for NIR emission enhancement are feasible at low cost and the NIR emissions produced here occur within the first biological window (700–1000 nm), which is of interest for biomedical applications.

LiBH4 hydrogen storage system with low dehydrogenation temperature and favorable reversibility promoted by metallocene additives

LiBH4 is of great potential as hydrogen storage material due to its high theoretical hydrogen storage capacity. However, it suffers from high thermal stability, sluggish dehydrogenation/hydrogenation kinetics and poor reversibility. Introduction of catalysts is an effective way to improve the hydrogen storage properties of LiBH4. In the present study, chromocene and nickelocene are used as catalytic additives to LiBH4 by a simple ball-milling. Nickelocene is mostly decomposed, forming CNTs (carbon nanotubes) cross-linking the LiBH4 particles, while chromocene maintains stable during the ball-milling process. But they are fully decomposed to Cr and Ni nanoparticles after the initial dehydrogenation and further transferred to CrB2 and Ni2B nanoparticles after initial hydrogenation. The in situ formed CrB2 and Ni2B show superfine nanoparticles and are uniformly dispersed in the matrix, acting as highly active catalysts. The dehydrogenation temperature of the combined system is evidently reduced, and the hydrogen storage kinetics and reversibility are significantly improved. The highly thermal conductive CNTs are considered helpful in heat transfer during dehydrogenation and hydrogenation. The method for the introduction of the catalysts is facile and low cost. The present work provides a new insight into the design of novel catalysts for LiBH4.

Controlling a defect structure of the ZnGa2O4:Cr3+ spinel through synthesis parameters for persistent luminescence optimization

ZnGa2O4:Cr3+ (ZGO:Cr) is one of the most promising red persistent phosphors for in-vivo imaging due to its 650–750 nm emission band in the range of the so-called first biological window. In this paper, we report on how to control the high brightness persistent luminescence of the smallest ZGO:Cr nanoparticles by optimization of hydrothermal synthesis parameters. The influence of pH solution, the temperature of synthesis, and calcination on the degree of inversion, lattice parameters, morphology, and crystallite size were systematically investigated. The results have shown that different synthesis conditions modify the trap depths distribution, by mixing the occupancy of Zn2+ and Ga3+ sites in the spinel structure, which affects the duration and intensity of persistent luminescence. The correlation between structural changes and optical properties is established and it is possible to control them by selecting the appropriate hydrothermal synthesis parameters.