Luminescent Nanomaterials Research Articles

Enhanced long-lasting luminescence nanorods for ultrasensitive detection of SARS-CoV-2 N protein

AbstractPersistent luminescence nanomaterials can remain luminescence when the light source is turned off, which exhibits promise in biosensor and bioimaging fields since they have the ability to completely eradicate tissue autofluorescence. Although significant progress has been made in the persistent luminescence biosensing, there is still a dearth of long-afterglow detection platform with low limit of detection (LOD) and high sensitivity. Herein, Zn2GeO4:Mn, Cr persistently luminescent nanorods (PLNRs) with superior persistent luminescence and long afterglow time were developed. The addition of Cr3+ manifestly improves persistent luminescence intensity and afterglow duration through creating a deep defect trap. Then the biosensors were constructed by combining the Zn2GeO4:Mn,Cr PLNRs-antibody and Fe3O4 magnetic nanoparticles (MNPs)-antibody for nucleocapsid protein detection based on electrostatic attraction. The LOD value for nucleocapsid protein realizes as low as 39.82 ag/mL, which is much lower than the previously reported persistent luminescent-based biosensors. Accordingly, the low detection sensitivity is attributed to fluorescence resonance energy transfer. In addition, high specificity is also achieved. Therefore, the as-prepared Zn2GeO4:Mn,Cr persistently luminescent materials can act as the promising candidate in biosensors applications. This strategy provides effective guidance for the development of biosensing platforms with high sensitivity and specificity.

Luminescent Multifunctional Nanomaterials: Capacitive Removal and Enhanced Detection Efficiency of Heavy Metals Ions for Advanced Water and Wastewater Treatment Application

AbstractIn recent years, heavy metal ions pollution in the industrialized environment of the societies threaten human health that flaunt ill‐sorted blueprints in freshwater resources obviously. The paradigm of designing luminescent multifunctional nanomaterials finds directions to the strategies of synthesizing cost‐effective, green, and versatile nanomaterials not only for detection, but also removal process of heavy metal ions in large scale applications. Among them, discovering the advances of luminescent multifunctional nanomaterials provides broad types of biomaterials, polymers and porous nanoparticles that grabs focal of investigations over the past several years due to their unique advantages such as enhanced detection efficiency with lowest limit of detection (LOD), minimum ions interference in versatile removal process, fast responsivity and selectivity as outstanding as unique physicochemical properties. This review paper tries to highlight the paradigm of principles for design, development, and utilization of luminescence nanomaterials for considering fundamental detection and removal mechanisms of heavy metal ions. In particular, these nanomaterials increase the remediation quality that are tackled in detail by focusing on opportunities and challenges in the field. Finally, design methods of these nanomaterials and concentrating on empowered detection and removal efficiency for heavy metals ions highlights novel prospective and strategies for largescale applications.

Luminescent nanomaterials for developing high-contrast latent fingerprints.

Fingerprint patterns (or epidermal ridges) are by far one of the most reliable techniques for individual identification. Fingerprint patterns get deposited on all kinds of solid surfaces due to human transudation or exudation process. Bodily fluids through sweat glands contain moisture, natural oils and proteins. Since latent fingerprint patterns are not readily recognizable they are collected from a crime scene and are further processed physically or chemically. Fingerprints obtained using conventional black and white powders face severe drawbacks including low sensitivity, high background interference from the substrates, involvement of toxic materials, and poor stability. To overcome the above-listed issues, especially for coloured and transparent substrates, luminescent materials have emerged as potential agents for rapid visualization of high-contrast latent fingerprints. This review covers the recent advancements in luminescent nanomaterials of both kinds (up and down conversion) and persistent nanophosphors for developing latent fingerprints. Special emphasis has been given to an unusual class of luminescent materials known as persistent nanophosphors, which do not require a constant excitation, thereby completely eradicating background noise. The review also covers different approaches to gathering fingerprints such as powder dusting, cyanoacrylate fuming, ninhydrin fuming and vacuum metal deposition.

Unravelling structural insights into ligand-induced photoluminescence mechanisms of sulfur dots.

Sulfur dots (S-QDs) hold promise as a new category of metal-free, luminescent nanomaterials, yet their practical application faces challenges primarily due to a limited understanding of their structure and its impact on their optical properties. Herein, by employing a spectrum of aliphatic and aromatic ligands, we identify the surface structure and composition of S-QDs while delineating the pivotal role of ligands in inducing photoluminescence. Thiol-functionalized ligands, such as 4-mercapto benzoic acid and glutathione, notably promote the formation of both green and blue luminescent S-QDs, boosting a high quantum yield of up to 56%. Further investigation on the synthesis of S-QDs with 4-mercapto benzoic acid unveils the dual role of H2O2: etching sulfur powder and oxidizing the -SH group to -SO2H. These oxidized ligands passivate the S-QD surface through hydrogen bonding. Electrospray ionization mass spectrometry analysis unveils the presence of distinct sulfur species such as [S4(C6H5SO2H)4(H2O)2H]+ and [S6(C6H5SO2H)6(H2O)3H]+, while XPS analysis confirms the existence of zerovalent sulfur and oxidized sulfur species including SO32- and SO42-. Further detailed spectroscopic examination demonstrates that S-QDs predominantly exist as aggregated entities, with the emission wavelength correlating with the degree of aggregation. The absence of photoluminescence in aggregations devoid of ligands underscores the critical role of ligands in the photoluminescence genesis of S-QDs.

Carbon dot unravels accumulation of triterpenoid in Evolvulus alsinoides hairy roots culture by stimulating growth, redox reactions and ANN machine learning model prediction of metabolic stress response

Evolvulus alsinoides, a therapeutically valuable shrub can provide consistent supply of secondary metabolites (SM) with pharmaceutical significance. Nonetheless, because of its short life cycle, fresh plant material for research and medicinal diagnostics is severely scarce throughout the year. The effects of exogenous carbon quantum dot (CD) application on metabolic profiles, machine learning (ML) prediction of metabolic stress response, and SM yields in hairy root cultures of E. alsinoides were investigated and quantified. The range of the particle size distribution of the CDs was between 3 and 7 nm. The CDs EPR signal and spin trapping experiments demonstrated the formation of O2-•spin-adducts at (g = 2.0023). Carbon dot treatment increased the levels of hydrogen peroxide and malondialdehyde concentrations as well as increased antioxidant enzyme activity. CD treatments (6 μg mL-1) significantly enhanced the accumulation of squalene and stigmasterol (7 and 5-fold respectively). The multilayer perceptron (MLP) algorithm demonstrated remarkable prediction accuracy (MSE value = 1.99E-03 and R2 = 0.99939) in both the training and testing sets for modelling. Based on the prediction, the maximum oxidative stress index and enzymatic activities were highest in the medium supplemented with 10 μg mL-1 CDs. The outcome of this study indicated that, for the first time, using CD could serve as a novel elicitor for the production of valuable SM. MLP may also be used as a forward-thinking tool to optimize and predict SM with high pharmaceutical significance. This study would be a touchstone for understanding the use of ML and luminescent nanomaterials in the production and commercialization of important SM.

Synthesis of YPO4:Tb3+ core-shell nanophosphors and their application in fingerprint detection

In order to enhance the fluorescent performance of rare-earth phosphates, YPO4:Tb3+ nanophosphors were synthesized using a one-step hydrothermal method, employing both homogeneous and heterogeneous coatings devoid of organic compounds. By adjusting the molar ratio of core to coating material, a series of core-shell structured luminescent nanomaterials YPO4:Tb3+@Y(Gd,La) LnPO4 (LnY, Gd and La) were prepared, and the optimal molar ratio to enhance the fluorescent performance of the YPO4:Tb3+ core was determined. Comprehensive analyses, employing techniques such as X-ray diffraction, scanning and transmission electron microscopy, fluorescence spectrophotometry, and ultraviolet spectrophotometry, characterized the composition, structure, morphology, and optical properties of the synthesized materials. Additionally, the energy bands and density of states of YPO4 were theoretically analyzed using first-principles calculations. These results indicate that the structure and morphology of the products was preserved post-coating, but the fluorescence intensity was significantly enhanced. Among them, the homogeneously coated YPO4:Tb3+@YPO4 nanophosphors exhibited the strongest fluorescence intensity, more than threefold that of the uncoated sample. Theoretical calculations confirmed that YPO4 is a direct bandgap phosphate with a calculated bandgap value of 5.88 eV, which is consistent with the experimental value. The prepared YPO4:Tb3+@YPO4 nanophosphors demonstrated clear potential in visualizing fingerprints on various materials; even fingerprints aged for 30 days were successfully visualized. Therefore, the coated nanophosphors not only enhance fluorescent performance but also broaden their applicability in latent fingerprint recognition.

Novel Type of Non‐Toxic, Degradable, Luminescent Ratiometric Thermometers Based on Dyes Embedded in Disulfide‐Bridged Periodic Mesoporous Organosilica Particles

AbstractDespite the excellent thermometric performance of many developed luminescent nanomaterials, their use has not gone beyond proof‐of‐concept in vivo experiments to date. An important issue that needs to be resolved before moving toward true biomedical applications of engineered nanothermometers is their potential toxicity and bioaccumulation in the human body considering the ultimate objective of clinical applications. Since most reported nanothermometers currently are not degradable materials and are mainly based on the incorporation of heavy metal ions, these aspects remain of genuine concern in the fields of nanomedicine, nanobiotechnology, nanotoxicology, and nanopharmacology. This work explores the possibility of designing visible, as well as near‐infrared, emitting luminescent ratiometric nanothermometers based on appropriate organic dye mixtures embedded in hollow disulfide‐bridged periodic mesoporous organosilica (PMO) particles. Such hybrid particles show excellent thermometric performance in the physiological temperature range (20–50 °C), favorable degradability in simulated physiological conditions, as well as no toxicity to healthy normal human dermal fibroblast (NHDF) cells in a wide concentration range. Considering the simplicity of the approach from the synthetic point of view, and the large available library of known fluorescent dyes emitting in various regions of the electromagnetic range, this motif renders a very promising approach to designing novel non‐toxic, decomposable, luminescent ratiometric thermometers.

Exploring Carbon Dots: Green Nanomaterials for Unconventional Lasing.

In recent years, the progress toward lighting miniaturization is focused on luminescent nanomaterials. Among them, fluorescent carbon dots (CDs) are receiving increasing attention thanks to their astonishing optical properties complemented by their intrinsic biocompatibility and low toxicity. The CDs can be easily dispersed in water, organic solvents or incorporated in polymeric matrices, preserving their emission properties. However, the relationship between their structural and optical properties is still not fully elucidated, motivating a consistent research effort for the comprehension of their features. Nevertheless, CDs demonstrate to be efficient gain materials for lasing, thanks to their high quantum yield (QY), emission tunability in the visible and near infrared (NIR) range, short lifetimes, and high absorption cross section, even if the synthetic reproducibility, the low reaction yield and the spectral width of the emission may limit their effective exploitation. This review summarizes the latest advancements in the investigation of the characteristic properties of CDs that make laser action possible, illustrating optical geometries for lasing and random lasing, both in solution and solid state, and the few currently demonstrated breakthroughs. While the journey toward their effective application is still long, the potential of CD-based laser sources is promising in various technological fields and futuristic perspectives will be discussed.

Impact of high sensitizer doping on the transient multiband upconversion luminescence in β-NaYF4:Yb/Ho microcrystals

Under intense near-infrared light excitation, upconversion luminescence (UCL) nanomaterials exhibit multiband emission and high sensitizer quenching concentration, indicating the potential to enhance upconversion (UC) quantum efficiency. In comparison to other common activator ions (e.g. Er3+, Tm3+, Ho3+), Ho3+ possesses abundant energy levels. However, previous studies mostly focused on the red (Ho3+:5F5 → 5I8) and green (Ho3+:5F4,5S2 → 5I8) emissions. In this paper, we have examined the transient UCL characteristics of β-NaYF4:Yb/Ho microcrystals (MCs) excited by a high-power 976 nm ns pulsed laser (∼0.32 GW/cm2). The energy transfer (ET) pathways with varying Yb3+ doping (20–98 mol%) are determined by the time evolution spectra. In high Yb3+ doping system (98 mol%), the electron population of Ho3+ accelerates, and the multiband UC rise is shortened by 6 times (from ∼3 μs to ∼500 ns). We identified a new pathway for electron populating with higher Yb3+ doping ( ≥ 40 mol%), which is Yb3+:2F5/2 + Ho3+:3L9 → Yb3+:2F7/2 + Ho3+:3M9. As Yb3+ concentration increases, the varying lifetime and intensity distribution of UCL leads to variations in the luminescence color evolution. Our result shows that altering the Yb3+ doping concentration provides a way to control the energy flow between energy levels of Ho3+, which can modulate the rise time and color evolution of Yb–Ho co-doped UC MCs. This study is expected to promote the advancement of fast-respond optoelectronic devices, UC displays, and micro-nano lasers. Kewordsmultiband upconversion luminescence; high-power excitation; upconversion luminescence dynamics; high sensitizer concentration; upconversion pathways.

(Invited) From Inside Out: How Synthesis-Structure Correlations Conspire to Determine Photoluminescence Traits and Operational Robustness in Non-Blinking Giant Quantum Dots

“Giant” or thick-shell core/shell quantum dots (gQDs) are an important class of solid-state quantum emitter. Without any encapsulation gQDs are characterized by strongly suppressed blinking, or even non-blinking behavior, and resistance to photobleaching at room temperature. In addition, non-radiative Auger processes are significantly reduced in this class of luminescent nanomaterial. Together, these qualities lead to novel functionality as photon sources for a range of ensemble and single-emitter applications, including down-conversion phosphors, direct excitation light-emitting diodes, single-biomolecule tracking, and single-photon generation. For many applications, operation at elevated temperature and under intense photon flux is also desired, and we have shown that gQDs outperform other emitters in this key metric of operational robustness. Interestingly, performance under these conditions is strongly dependent on the synthetic method employed for shell growth. Previously we revealed the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging (ACS Nano 2018, 12, 5, 4206), and subsequently used solid-state spectroscopy to obtain kinetic and thermodynamic parameters of the photothermal degradation process (ACS Appl. Mater. Interfaces 2020, 12, 27, 30695). Here, I will discuss a comprehensive analysis of gQD structural properties from the inside of the nanocrystal to its surface and demonstrate correlations between specific structural features and both causal synthetic parameters and resulting performance metrics. Two synthetic methods—successive-ionic-layer-adsorption-and-reaction and high-temperature continuous-injection—will be compared. Investigated structural features will include interfacial alloying, stacking-fault density and surface-ligand identity, while correlated functionalities will address quantum yield, single-gQD photoluminescence under thermal/photo-stress, charging behavior and quantum-optical properties. I will show several unexpected conclusions, including the surprising finding that while interfacial alloying is the strongest indicator of gQD stability under stress, the parameter is not the determining factor for Auger suppression. Furthermore, quantum yield is strongly influenced by surface chemistry and can approach unity even in the case of a gQD comprising a thick shell with a high defect density with proper choice of excitation wavelength. Interestingly, we find a strong correlation between the existence of zinc-blende stacking faults and whether the gQD exhibits charged-state or purely excitonic emission, and the interplay between charged emission and excitonic emission can be precisely tuned by “mixing” shell-growth methods (Small Sci. 2023,3, 2300092).

A solvothermal method for the synthesis of dual paramagnetic and upconverting luminescent β-NaYF4:Yb3+,Ln3+@NaGdF4 (Ln3+=Er3+ or Tm3+) core@shell nanoparticles

The interest in the applications of upconverting luminescent nanomaterials has expanded significantly, particularly in the biomedical field. An opportunity for innovation in this realm lies in the development of multimodal contrast agents that exhibit both luminescent and magnetic responses. This study presents an easily reproducible strategy for the solvothermal synthesis of NaYF4:Yb3+,Ln3+@NaGdF4 (Ln = Er3+ or Tm3+) core@shell nanoparticles. The shell incorporation process initially involved dissolving the outer layer of NaYF4:Yb3+,Ln3+ cores, followed by the radial growth of NaGdF4 around them. This shell provides intense paramagnetic properties without affecting the luminescent response of the cores. The optimized process yielded individual core@shell nanoparticles, with average diameters of 20 ± 5 nm for NaYF4:Yb3+,Er3+@NaGdF4 and 19 ± 3 nm for NaYF4:Yb3+,Tm3+@NaGdF4 UCNPs. The presence of NaGdF4 shells was further confirmed by Raman spectroscopy, which revealed a change in polarizability within the structure due to the presence of Gd3+ instead of Y3+. Based on the hysteresis loops, the magnetic response of NaYF4:Yb3+,Ln3+ was negligible, whereas NaYF4:Yb3+,Ln3+@NaGdF4 exhibited saturation at 1.04 emu/g at 20 kOe. Compared to common thermal decomposition approaches, this method offers several advantages: it provides nanoparticles that are colloidally stable in aqueous solutions, a higher reaction yield, eliminates the need for an inert atmosphere, reduces the excessive use of solvents for separation and washing, and requires less experimental manipulation. Therefore, this method enables the synthesis of materials with applications in the development of sensors, contrast agents, or theranostic tools with dual magnetic-luminescent responses.

Solvent-Assisted Structural Modifications of Sulfur Dots Followed by Time-Dependent Emergence of a New Emissive State and Long-Lived Afterglow.

Sulfur dots are a new class of recently developed nonmetallic luminescent nanomaterials with various potential applications. Herein, we synthesized sulfur dots using a mild chemical etching method and then modified the structural features of the as-synthesized sulfur dots using a slow and defined solvent-assisted aggregation process. This increases the particle size and overall crystallinity along with the modifications of the surface functional groups, which eventually show a new emission band at longer wavelengths. Detailed photophysical and temperature-dependent luminescence studies confirmed that the new emissive state evolves due to interparticle interactions in the excited state. Furthermore, the occurrence of a new emissive state in a longer-wavelength region helped reduce the energy gap between the lowest excited singlet state and the lowest excited triplet state in modified sulfur dots, resulting in an aqueous stable room-temperature phosphorescence/afterglow emission through efficient intersystem crossing. This typical efficacious afterglow emission directly shows the potential applicability of structurally modified sulfur dots in encryption devices and can also be potentially effective in light emitting diodes (LED) and sensing devices.

Antimicrobial activity and mechanisms of carbon quantum dot decorated modified zinc oxide nanoparticles against oral pathogenic bacteria

Caries represents one of the most prevalent bacterial infectious diseases in the oral cavity. Over decades, researchers have been actively seeking nanomaterials capable of inhibiting oral pathogenic bacteria. We utilized a one-pot hydrothermal method to synthesize CQDs with multicolor luminescence and CQD-loaded ZnO composite nanomaterials. FE-SEM revealed that the rod-like structure of CQDs/ZnO becomes finer with increased CQDs content. XRD and XPS confirmed the presence of all components within the nanocomposites. We compared the antimicrobial activities of ZnO, 7.7% and 14.3% CQDs/ZnO against Streptococcus mutans, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus. The 7.7% CQDs/ZnO composite exhibited the most effective antibacterial activity. The 7.7% CQDs/ZnO composite exhibited the most effective antibacterial activity. FE-SEM and ONPG assays demonstrated that 7.7% CQDs/ZnO disrupted the membrane structure and alters membrane permeability. ESR, DPBF and ROS assayed further confirmed that 1O2 produced by 7.7% CQDs/ZnO accumulated at the cell membrane and disrupts its structure.

Assessment of luminescent copper nanomaterials as anti-germs, anti-proliferation efficiencies using green nano-strategy.

For the first time, we suggest using leaf extract from Ocimum americanum as the economically viable bio-fabrication of copper nanomaterials. The residuals of leaf extract bio-capping provide the stability of the nanomaterials in-situ. UV-Vis and XRD confirmed the formation, with the UV-Vis spectrum of Cu-NMs revealing a surface plasmon resonance characteristic peak at 350 nm. FT-IR analysis was employed to examine the functional groups. FE-SEM with EDX was used to assess the morphology and carry out an elemental analysis of the nanomaterials. Diffusion and MTT assays were used to study the antimicrobial and anticancer activities. The synthesized copper nanomaterials exhibited in-vitro cytotoxicity against human skin cancer (A431) cell lines. Green nanomaterial was examined against the methylene blue dye, photodegradation was reduced by up to 90.6% within 50 minutes. The copper nanomaterials synthesized in our study exhibit promising applications in biomedicine and environmental pollution research.

Detection of ascorbic acid by persistent luminescent nanoparticles based on CoOOH nanosheets modification.

Persistent luminescent nanomaterials (PLNPs) Zn0.8Ga2O4: Cr3+, Zr3+ with high brightness and good dispersion were prepared by hydrothermal method. The PLNPs were used as luminescent units, and CoOOH nanosheets were used as quenching agents. Based on the fluorescence internal filtering effect, the luminescence of PLNPs were effectively quenched by CoOOH modification on the surface of PLNPs. However, the introduction of ascorbic acid (AA) restored the luminescence of PLNPs and successfully achieved highly sensitive and selective detection of AA. This was due to a selective redox reaction between CoOOH and AA, in which CoOOH was reduced to Co2+. The degree of luminescence recovery of PLNPs showed a good linear relationship with AA concentration in the range 5-250 µM, with a detection limit of 0.72 µM. Therecovery of actualspikedsamples were 97.9-102.2%. This method isexpected to provide reference for the study of other redox substances in biological systems.

Bioelectrocatalytic Activity of One-Dimensional Porous Pt Nanoribbons for Efficient Inhibition of Tumor Growth and Metastasis.

Designing and synthesizing one-dimensional porous Pt nanocrystals with unique optical, electrocatalytic, and theranostic properties are gaining lots of attention, especially to overcome the challenges of tumor recurrence and resistance to platinum-based chemotherapy. Herein, we represented an interesting report of a one-step and facile strategy for synthesizing multifunctional one-dimensional (1D) porous Pt nanoribbons (PtNRBs) with highly efficient therapeutic effects on cancer cells based on inherent electrocatalytic activity. The critical point in the formation of luminescent porous PtNRBs was the use of human hemoglobin (Hb) as a shape-regulating, stabilizing, and reducing agent with facet-specific domains on which fluorescent platinum nanoclusters at first are aggregated by aggregation-induced emission phenomena (AIE) and then crystallized into contact and penetration twins, as intermediate products, followed by shaping of the final luminescent porous ribbon nanomaterials, owing to oriented attachment association via the Ostwald ripening mechanism. From a medical point of view, the key strategy for effective cancer therapy occured via using low-dosage ethanol in the presence of electroactive porous PtNRBs based on intracellular ethanol oxidation-mediated reactive oxygen species (ROS) generation. The role of heme groups of Hb, as electrocatalytically active centers, was successfully demonstrated in both kinetically controlled anisotropic growth of NRBs for slowing down the reduction of Pt(II) followed by oligomerization of Pt(II)-Hb complexes via platinophilic interactions as well as electrocatalytic ethanol oxidation for therapy. Interestingly, hyaluronic acid-targeted (HA) Hb-PtNRB in the presence of low-dose ethanol caused extraordinary arrest of tumor growth and metastasis with no recurrence even after the treatment course stopped, which caused elongation of tumor-bearing mice survival. HA/Hb-PtNRB was completely biocompatible and exhibited high tumor-targeting efficacy for fluorescent imaging of breast tumors. Therefore, the synergistic electrocatalytic activity of PtNRBs is presented as an efficient and safe cancer theranostic method for the first time.

Multi-mode photoluminescence inks based on lanthanide-doped multilevel core-shell microspheres for advanced anti-counterfeiting applications

Development of advanced luminescent nanomaterials and technologies is of great significance for anticounterfeiting applications in global economy, security, and human health. In this work, we have designed two types of anti-counterfeit materials. (1) The dual excitation mode core–shell microsphere is based on SiO2 core, with the GdVO4:Yb,Er upconversion luminescent inner layer, SiO2 shell separator, and Gd2O3:Eu@SiO2 downconversion luminescent layer are sequentially deposited on it via co-precipitation method. The microspheres have a five-layer core–shell structure with an overall diameter of ∼ 146 nm and enables the spatial separation of Er3+ and Eu3+, which prevents the cross-relaxation of Er3+. The microspheres were prepared into an upconversion/downconversion excitation mode luminescent ink, with inkjet-printed patterns that only extract information when excited by 254 nm and 980 nm excitation. (2) The core–shell-shell SiO2@AIPA-S-Si-Tb@SiO2 microspheres have been synthesized by using organic ligands ((HOOC)2C6H3NHCONH(CH2)3Si(OCH2CH3)3) (defined as AIPA-S-Si) connected with Tb3+ ions and silica through covalent bond. The microspheres have a sandwich structure with an overall diameter of ∼ 100 nm and show bright green light. The sandwich structure and five-layer core–shell structure was mixed proportionally to obtain orange-red, white, and yellow emission ink under 254 nm, green emission under 310 nm, and green emission under 980 nm excitation.

Stimuli-responsive photoluminescent and structural properties of MIL-53(Al) MOF for sensing applications

Metal–organic frameworks (MOFs) are an intriguing group of porous materials due to their potential influence on the development of indispensable technologies like luminescent sensors and solid-state light devices, luminescent multifunctional nanomaterials. In this research work we explored MIL-53(Al), an exceptional class of MOF that, along with guest adsorption, undergoes structural transitions exhibiting breathing behavior between narrow pore and large pore under temperature and mechanical stress. Therefore, we opted for the time resolved luminescence and FT-Raman spectroscopy to investigate the mechanochromic and thermochromic response of this material under external stimuli. Intriguingly, when subjected to temperature changes, MIL-53(Al) exhibited a ratiometric fluorescence behavior related to the reversible relationship of photoluminescence emission intensity with respect to temperature. Moreover, under higher mechanical stress MIL-53(Al) displayed turn-on behavior in emission intensity, hence offering a thrilling avenue for the application in mechanically deformed-based luminescent sensors and ratiometric fluorescence temperature sensors.

From synthesis to applications of biomolecule-protected luminescent gold nanoclusters.

Gold nanoclusters (AuNCs) are a class of novel luminescent nanomaterials that exhibit unique properties of ultra-small size, featuring strong anti-photo-bleaching ability, substantial Stokes shift, good biocompatibility, and low toxicity. Various biomolecules have been developed as templates or ligands to protect AuNCs with enhanced stability and luminescent properties for biomedical applications. In this review, the synthesis of AuNCs based on biomolecules including amino acids, peptides, proteins and DNA are summarized. Owing to the advantages of biomolecule-protected AuNCs, they have been employed extensively for diverse applications. The biological applications, particularly in bioimaging, biosensing, disease therapy and biocatalysis have been described in detail herein. Finally, current challenges and future potential prospects of bio-templated AuNCs in biological research are briefly discussed.

Construction of active-inert core–shell structured nanocrystals for broad range multicolor upconversion luminescence

Rare earth doped up-conversion luminescent nano-materials exhibit abundant emission colors under suitable excitation condition. In this work, NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanoparticles were synthesized by co-precipitation method. The pure red emission can be realized by the designed NaYF4:Er/Ho@NaYF4 nanocrystals and the R/Gs reach 23.3 and 25 under excitations of 980 and 1550 nm lasers, respectively. The R/G declines as the power increasing with the emission color changing from red to yellow, which is due to the quick saturation of the energy levels, radiating red emissions. Meanwhile, the emission intensity of NaYbF4:Tm@NaYF4 nanocrystals increases by 58.3 folds after encasing the inert shell NaYF4 and the CIE color coordinate reaches (0.1646, 0.0602) under 980 nm laser excitation. Furthermore, broad range multicolor from blue to red and yellow up-conversion emissions is achieved by mixing NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanocrystals, which could be applied to colorful displaying, security anti-counterfeiting and information coding.