Change In Photoluminescence Intensity Research Articles

Static and dynamic strain-driven photoluminescence tuning in rare-earth doped perovskite oxide thin films

Recently, there have been significant interest in the wide potential of photoluminescence (PL) response of rare-earth doped perovskite oxide thin films in the field of optoelectronics. This work reports an effective method to modulate the PL properties of 0.8 mol%Sm3+-doped BaTiO3 (BTO:Sm) thin films through static and dynamic strain. BTO:Sm films were epitaxially grown on LaAlO3 (LAO), 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT), MgO, and Mica single-crystal substrates by pulsed laser deposition technique. Compared with the BTO:Sm/PMN-PT heterostructure which experiences minimal lattice mismatch effect, the PL intensity of BTO:Sm/LAO and BTO:Sm/MgO is enhanced by 818.1% and 1014.7%, respectively, due to static tensile/compressive strain (-0.429% and 0.461%) during the epitaxial growth process. In the flexible BTO:Sm/Mica heterostructure, dynamic strain is introduced through mechanical bending. Compared with the unbent state, the u-type and n-type bending modes increase the relative changes in PL intensity (ΔI/I) by 599.0% and 768.5%, respectively. Particularly, BTO:Sm/Mica also exhibits a remarkable optical transmittance exceeding 75% (500–2500 nm). The enhancement of PL intensity is closely related to the adjustment of lattice strain, which changes the crystal field strength of the BTO:Sm and the radiative transition probability. This work provides valuable insights for designing future optoelectronic devices and environmental monitoring equipment. It has the potential to advance photonics and sensor technologies, paving the way for innovation and exploration in these fields.

Multi-Stimuli-Responsive photoluminescence of cesium manganese bromide by temperature and solvent-induced structural phase transitions

Metal halide perovskites showing responses to external stimuli have emerged as a new class of stimulus-responsive smart materials. Specifically, their photoluminescence (PL) intensity, color and lifetime can change with different external stimuli. However, most of the existing metal halide perovskites only show PL response to a single stimulus. For encryption security applications, it is desired to have selective PL response to multiple stimuli. Herein, we developed a new type of cesium (Cs) manganese (Mn) bromide (Br) perovskite (Cs2MnBr4(H2O)2) single crystal with PL response to temperature, humidity and solvent by taking advantage of its structural phase transition, which causes its PL intensity (from non-luminescent to near unity luminescence) and color change (from green to red). Stimuli-responsive PL can be achieved by engineering the phase structure of Cs-Mn-Br perovskites from Cs2MnBr4(H2O)2 to Cs2MnBr4, Cs3MnBr5, CsMnBr3(H2O)2 and CsMnBr3 via temperature and different solvents. Such multiple stimuli responsive material is promising for multidimensional information encryption.

Structural and spectroscopic studies of lithium tetraborate glass co-doped with Sm and Cu.

The local structure and spectroscopic properties of Cu-Sm co-doped Li2B4O7 glass have been studied using XRD, EPR, UV-Vis-NIR absorption and luminescence methods and compared with the corresponding results for Sm-doped and Cu-doped Li2B4O7 glasses. The EPR spectrum reveals an axially-symmetric signal with a characteristic hyperfine structure belonging to Cu2+ ions. The Cu2+/Cutotal ratio was determined. The optical absorption spectrum shows a broad, intense band attributed to Cu2+ ions and several weaker narrow bands attributed to Sm3+ ions. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra as well as PL decay kinetics of Sm3+ and Cu+ ions were registered, analyzed, and discussed. The PL spectra show a broad band assigned to the 3d94s1 → 3d10 transition of Cu+ ions and four narrow bands assigned to the 4G5/2 → 6HJ (J = 5/2-11/2) transitions of Sm3+ ions. The observed changes in PL intensity, shortening of the Sm3+ lifetime and prolongation of the Cu+ lifetime were explained by energy transfer from Sm3+ → Cu+ and re-absorption of the Sm3+ emission by Cu2+ ions.

Deep-red photoluminescent mechanoresponsive polymers with dynamic CuI-arylamide mechanophores.

We demonstrate the use of copper arylamide complexes as efficient photoluminescent mechanophores to design deep-red/near-IR emissive polymers showing reversible changes in photoluminescence intensity in the red/near-IR region in response to mechanical stretching. The mechanoresponse was repeatable over 30 cycles, showing a measurable increase of photoluminescence intensity even at a small applied stress of ca. 0.01 MPa. We demonstrate the potential of using conformationally dynamic copper amide complexes as sensitive and reversible mechanophores for near-IR imaging; systematic control over the emission range was achieved using amide modification.

Controlling photoluminescence of silicon quantum dots using pristine-nanostates formation

This study investigates the effective control of photoluminescence (PL) of silicon nanocrystals (Si–NCs) embedded in a SiO2 matrix, with a specific focus on tuning the luminescent wavelength profile and intensity for silicon-based optoelectronic applications. By manipulating the composition ratio (x) of SiOx, the well-known simultaneous changes in PL peak position and intensity were observed after annealing. To preserve the desired wavelength characteristics and enhance the luminesce intensity, we propose a novel approach to generate pristine nanostates (PNs) for Si-NC formation using proton irradiation (PI). The application of proton irradiation was found to be successful in significantly increasing PL intensity while strongly suppressing the peak position shifts. Through extensive spectroscopic analysis including PL, X-ray photoelectron spectroscopy, and absorption spectroscopy, we investigate specific defect states in the SiOx matrix, and identified as PNs. We interpret that these PNs consist of self-trapped exciton, E′ center, non-bridging oxygen hole center, and oxygen-deficiency center states. In the as-grown sample, the PNs promote appropriate phase separation and play a significant role in stabilizing the structure during the subsequent annealing processes. This study elucidates the Si-NC formation mechanism by enhancing O-diffusion-induced phase separation, a process accelerated in SiOx with controlled PNs. The proposed PI-induced PNs offer a novel pathway for developing Si-based optoelectronic devices with desired characteristics in the operating wavelength range. These findings open up promising possibilities for advanced silicon-based optoelectronic applications.

Intensity Dependent Photoluminescence Imaging for In‐Line Quality Control of Perovskite Thin Film Processing

AbstractLarge area fabrication of high‐quality polycrystalline perovskite thin films remains one of the key challenges for the commercial readiness of perovskite photovoltaic (PV). To enable high‐throughput and high‐yield processing, reliable and fast in‐line characterization methods are required. The present work reports on a non‐invasive characterization technique based on intensity‐dependent photoluminescence (PL) imaging. The change in PL intensity as a function of excitation power density can be approximated by a power‐law with exponent k, which is a useful quality indicator for the perovskite layer, providing information about the relative magnitudes of radiative and non‐radiative recombination. By evaluating k‐parameter maps instead of more established PL intensity images, 2D information is obtained that is robust to optically induced artifacts such as intensity variations in excitation and reflection. Application to various half stacks of a perovskite solar cell showcase its ability to determine the importance of the interface between the charge transporting and perovskite layers. In addition, the k‐parameter correlates to the bulk passivation concentration, enabling rapid assessment of open‐circuit voltage variations in the range of 20 mV. Considering expected improvements in data acquisition speed, the presented k‐imaging method will possibly be obtained in real‐time, providing large‐area quality control in industrial‐scale perovskite PV production.

First-principles investigation of divalent ion sensing with cesium lead trihalides

The first-principles calculations of the cesium lead trihalides, CsPbX3 (X = Cl, Br and I), doped with divalent ions such as Cd2+, Cu2+, Mg2+, Ni2+, Sn2+ and Zn2+ are carried out within the density functional theory to explore ion-sensing ability of CsPbX3 for divalent ions. Here the formation energy of the divalent ions doped CsPbX3 are calculated to evaluate the ability of absorption of the divalent ions. To investigate change in photoluminescence intensity of CsPbX3 due to the divalent ions incorporation, change in electronic structures of CsPbX3 due to the divalent ions dopings are also discussed by comparing the calculated electronic density of states.

Glutathione-Capped ZnS Quantum Dots-Urease Conjugate as a Highly Sensitive Urea Probe

Quantum dots (QDs) possess characteristic chemical and optical features. In this light, ZnS QDs capped with glutathione (GSH) were synthesized via an easy aqueous co-precipitation technique. Fabricated QDs were characterized in terms of X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Fourier transform infrared (FTIR) and Zeta potential analyses. Optical properties were examined using photoluminescence (PL) and ultraviolet–visible (UV–visible) spectroscopies. Moreover, GSH-capped ZnS QDs were evaluated as an optical probe for non-enzymatic detection of urea depending on the quenching of PL intensity of ZnS QDs in the presence of urea from concentration range of 0.5–5 mM with a correlation coefficient (R2) of 0.995, sensitivity of 0.0875 mM−1 and LOD of 0.426 mM. Furthermore, GSH-capped ZnS QDs-urease conjugate was utilized as an optical probe for enzymatic detection of urea in the range from 1.0 µM to 5.0 mM. Interestingly, it was observed that urea has a good affinity towards ZnS QDs-urease conjugate with a linear relationship between the change of PL intensity and urea concentration. It was found that R2 is 0.997 with a sensitivity of 0.042 mM−1 for mM concentration (0.5–5 mM) and LOD of 0.401 mM. In case of µM concentration range (1–100 µM), R2 was 0.971 with a sensitivity of 0.0024 µM−1 and LOD of 0.687 µM. These data suggest that enzyme conjugation to capped QDs might improve their sensitivity and applicability.Graphical

The detection of the captured circulating tumor cells on the core-shell nanofibrous membrane using hyaluronic acid-functionalized graphene quantum dots.

In recent years, cancerous cases have increased remarkably worldwide, and metastasis is the leading cause of death. Therefore, research on the early detection of cancer and metastasis has expanded to aid successful cancer treatment. Here in this paper, at the first step, an electrospun nanofibrous membrane (NFM) with a core-shell structure was fabricated from PCL and HA to achieve cancer cell capturing (about 75% of cells). On the other hand, hyaluronic acid (HA)-functionalized graphene quantum dots (GQDs) were used to detect captured cancer cells on NFM through the changes in photoluminescence intensity. Therefore, CD44 receptor-HA interaction is the main principle used for both entrapment and detection of cancer cells. Results demonstrated the GQD-HA fluorescent intensity of solution decreased through the increase of the captured cancer cell numbers on NFM, which is related to the more adsorption of GQD nanocomposites to the CD44 receptors. In contrast, this intensity for noncancerous cells was steady with any cell concentrations. This difference shows the system's remarkable selectivity and specificity, which can be crucial in fluorescent imaging for accurate cancer diagnosis.

Optical and quantitative detection of cobalt ion using graphitic carbon nitride-based chemosensor for hydrometallurgy of waste lithium-ion batteries

A hydrometallurgy is one of the most important techniques for recycling waste LIBs, where identifying the exact composition of the metal-leached solution is critical in controlling the metal extraction efficiency and the stoichiometry of the regenerated product. In this study, we report a simple and selective optical detection of high-concentrated Co2+ using a graphitic carbon nitride (g–CN)–based fluorescent chemosensor. g-CN is prepared by molten salt synthesis using dicyandiamide (DCDA) and LiI/KI. The mass ratio of LiI/KI to DCDA modifies the resulting g-CN (CNI) in terms of in-plane molecular distances of base sites including cyano functional groups (─CN) and fluorescent emission wavelength via nucleophilic substitution. The fluorescent sensing performance of CNIs is evaluated through photoluminescence (PL) emission spectroscopy in a broad Co2+ concentration range (10−4–100 M). The correlation between the surface exposure of hidden nitrogen pots (base sites) and PL intensity change is achieved where the linear relationship between the PL quenching and the logarithm of Co2+ concentration in the analyte solution is well established with the regression of 0.9959. This study will provide the design principle of the chemosensor suitable for the fast and accurate optical detection of Co2+ present in a broad concentration range for hydrometallurgy for the recycling of waste LIBs.

Energy storage and photoluminescence properties of Sm<sup>3+</sup>-doped 0.94Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-0.06BaTiO<sub>3</sub> multifunctional ceramics

In recent years, inorganic multifunctional ferroelectric ceramics have been widely utilized in various fields, including aerospace, optical communication, and capacitors, owing to their high stability, easy synthesis, and flexibility. Rare-earth doped ferroelectric materials hold immense potential as a new type of inorganic multifunctional material. This work focuses on the synthesis of <i>x</i>%Sm<sup>3+</sup>-doped 0.94Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-0.06BaTiO<sub>3</sub> (BNTBT:<i>x</i>%Sm<sup>3+</sup> in short) ceramics by using the conventional solid-state sintering method, aiming to comprehensively investigate their ferroelectric, energy storage, and photoluminescence (PL) properties. The X-ray diffraction analysis reveals that the introduction of Sm<sup>3+</sup> does not trigger off the appearing of secondary phases or changing of the original perovskite structure. The scanning electron microscope (SEM) images demonstrate that Sm<sup>3+</sup> incorporation effectively restrains the grain growth in BNTBT, resulting in the average grain size decreasing from 1.16 to 0.95 μm. The reduction in remanent polarization (<i>P</i><sub>r</sub>) and coercive field (<i>E</i><sub>c</sub>) can be attributed to both the grain size refinement and the formation of morphotropic phase boundaries (MPBs). Under an applied field of 60 kV/cm, the maximum value of energy storage density (<i>W</i><sub>rec</sub>) reaches to 0.27 J/cm<sup>3</sup> at an Sm<sup>3+</sup> doping concentration of 0.6%. The energy storage efficiency (<i>η</i>) gradually declines with electric field increasing and stabilizes at approximately 45% for Sm<sup>3+</sup> doping concentrations exceeding 0.6%. This result can be ascribed to the decrease in Δ<i>P</i> (<i>P</i><sub>max</sub><sub> </sub>– <i>P</i><sub>r</sub>) due to the growth of ferroelectric domains as the electric field increases. Additionally, all Sm<sup>3+</sup>-doped BNTBT ceramics exhibit outstanding PL performance upon being excited with near-ultraviolet (NUV) light at 408 nm, without peak position shifting. The PL intensity peaks when the Sm<sup>3+</sup> doping concentration is 1.0%, with a relative change (Δ<i>I/I</i>) reaching to 700% at 701 nm (<sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>11/2</sub>). However, the relative change in PL intensity is minimum at 562 nm (<sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>5/2</sub>) due to the fact that the <sup>4</sup>G<sub>5/2</sub>→<sup>6</sup>H<sub>5/2</sub> transition represents a magnetic dipole transition, and the PL intensity remains relatively stable despite variations in the crystal field environment surrounding Sm<sup>3+</sup>. Our successful synthesis of this novel ceramic material, endowed with both energy storage and PL properties, offers a promising avenue for developing inorganic multifunctional materials. The Sm<sup>3+</sup>-doped BNTBT ceramics hold considerable potential applications in optical memory and multifunctional capacitors.

Optical gas sensor based on the combination of a QD photoluminescent probe and a QD photodetector

We report on a sensor architecture for detection of hazardous gases. The proposed device is based on the integration of a solid-state quantum dot (QD) photoluminescent probe with a QD photodetector on the same substrate. The effectiveness of the approach is demonstrated by developing a compact optical sensor for trace detection of explosives in air. The proposed architecture is very simple and consists of a silicon substrate with both surfaces coated with QD films. The upper layer acts as photoluminescent probe, pumped by a blue LED. The change of photoluminescence intensity associated to the interaction between the QDs and the target analyte is measured by the QD photodetector fabricated on the opposite side of the substrate. The sensor is mounted into a small chamber provided with the LED and the front-end electronics. The device is characterized by using nitrobenzene as representative nitroaromatic compound. Extremely low concentrations (down to 0.1 ppm) can be detected by the proposed device, with a theoretical detection limit estimated to be as low as 2 ppb. Results are repeatable and no ageing effect is observed over a 70 d period. The proposed architecture may provide a promising solution for explosive detection in air as well as other sensing applications, thanks to its sensitivity, simple fabrication process, practical usability and cost effectiveness.

Synthesis, enhanced photoluminescence, and multifunctional applications of CaSr2(VO4)2:Sm3+ phosphor via co-doping with alkali metal (Li+, Na+, K+) ions

In this work, CaSr2(VO4)2 phosphors singly doped with Sm3+ ions and co-doped with alkali metal (Li+, Na+, and K+) are prepared by using the high temperature solid state reaction. The X-ray diffraction (XRD) patterns exhibit that all the samples belong to the rhombohedral CaSr2(VO4)2 phase with a space group of R3c (161). Upon excitation with the near-ultraviolet (UV) light, the characteristic Sm3+ emission lines, with the peak dominated at 605 nm, are achieved. Importantly, the photoluminescence (PL) intensity of Sm3+ ions can be enhanced significantly by co-doping with Li+, Na+, and K+ ions, and the reason can be attributed to the charge-compensated role of the alkali metal ions. Furthermore, the temperature-dependent PL experiments measured in the range of 298–573 K show that the optimal phosphor feature excellent stability against heat, making it suitable for acting as a UV-excited orange-red component for phosphor-converted wLEDs (pc-wLEDs). Besides, the PL intensity change of Sm3+ between 4F3/2 → 6H5/2 (531 nm) and 4G5/2 → 6H5/2 (562 nm), 4F3/2 → 6H5/2 (531 nm) and 4G5/2 → 6H7/2 (605 nm), and 4F3/2 → 6H5/2 (531 nm) and 4G5/2 → 6H9/2 (645 nm) is also analyzed further in the temperature range from 298 K to 973 K, and the results show that the obtained phosphors are suitable for applying in thermometry. Obviously, we reveal multifunctional applications of the obtained phosphors for UV-excited pc-wLEDs and thermometry.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Pulsed laser deposition and structural evolution of BaF2 nanolayers in Eu-doped BaF2/Al2O3 layered optical nanocomposite thin films

We have developed a pulsed laser deposition (PLD) geometry for the growth of uniform BaF2 nanoscale thin films, through control of the deposition conditions. Our goal is to use the BaF2 layers with controllable structure as component layers in layered optical nanocomposites. The structure of the BaF2 nanolayer evolves as a function of the layer thickness: BaF2 grows via a layer-by-layer growth mode on Al2O3; the layers are amorphous for a thickness < 3 nm, and then become nanocrystalline as the layer thickness increases. The BaF2 nanocrystals have an FCC crystal structure with a weak <111> texture that becomes stronger for thicker films. We then demonstrate that our BaF2 films can be introduced into layered Al2O3/BaF2/EuOx nanocomposite films, which allows for control of the relative position of the Eu ions and the BaF2 layer. Cross-section samples of the multilayered films show interfacial intermixing between the layers, which is related to implantation during the PLD process. This intermixing enables the incorporation of Eu ions into BaF2 layers and form a thin Eu-doped BaF2 nanolayer at the interface. The layered nanocomposite films show photoluminescence (PL) emission from Eu3+ ions, and the PL intensity changes can be correlated with the crystallinity and crystal size changes in the BaF2 layer. Our results provide guidance for achieving thin film nanocomposite materials with controllable structure and photoluminescence behavior for light emitting diodes, photovoltaics and other optical applications.

Halogen‐content‐dependent photoluminescence of Mn2+‐doped CsPbCl3 nanocrystals

AbstractThe thermodynamically viable halogen vacancy defects in CsPbCl3 perovskite nanocrystals (NCs) are considered the main factor in weakening their optical quality. However, their separate impact on the dopant emission in Mn2+‐doped CsPbCl3 perovskite NCs is still under exploration owing to the absence of comparable samples. Herein, a series of Mn2+‐doped CsPbCl3 samples were synthesized with different oleylamine‐Cl (OAm‐Cl) contents based on a halogen‐hot‐injection strategy. It is found that the Mn2+ concentration of as‐prepared samples fixed at 0.65%, and the Mn2+ photoluminescence (PL) also exhibited an OAm‐Cl content‐independent lifetime of ∼ 1.78 ms, implying the efficient and identical luminescence of isolated Mn2+ ion in all samples. In contrast, the excitonic and Mn2+ PL intensities of the NCs are strong related to the amount of OAm‐Cl, which are attributed to the coordination effect of the suppressed excitonic nonradiative recombination owing to the passivation of chloride vacancies and the enhanced energy transfer from the host exciton to Mn2+ ions in the samples with sufficient OAm‐Cl contents. The temperature‐dependent of Mn2+ PL disclosed an initial increase and was followed by a decrease with increasing temperature for the samples with relatively higher OAm‐Cl contents, while it monotonously decreases for the sample with lower OAm‐Cl content of 0.4 mL. The different PL intensity change trend results from the effective passivation of chloride vacancies by extra OAm‐Cl. Above results present here will help clarify the underlying influence mechanism of halogen vacancy on the PL properties of Mn2+‐doped perovskite NCs, which is essential for targeted modulation of their optical properties.

Membrane potential sensing: Material design and method development for single particle optical electrophysiology.

We review the development of "single" nanoparticle-based inorganic and organic voltage sensors, which can eventually become a viable tool for "non-genetic optogenetics." The voltage sensing is accomplished with optical imaging at the fast temporal response and high spatial resolutions in a large field of view. Inorganic voltage nanosensors utilize the Quantum Confined Stark Effect (QCSE) to sense local electric fields. Engineered nanoparticles achieve substantial single-particle voltage sensitivity (∼2% Δλ spectral Stark shift up to ∼30% ΔF/F per 160 mV) at room temperature due to enhanced charge separation. A dedicated home-built fluorescence microscope records spectrally resolved images to measure the QCSE induced spectral shift at the single-particle level. Biomaterial based surface ligands are designed and developed based on theoretical simulations. The hybrid nanobiomaterials satisfy anisotropic facet-selective coating, enabling effective compartmentalization beyond non-specific staining. Self-spiking- and patched-HEK293 cells and cortical neurons, when stained with hybrid nanobiomaterials, show clear photoluminescence intensity changes in response to membrane potential (MP) changes. Organic voltage nanosensors based on polystyrene beads and nanodisk technology utilize Fluorescence (Förster) Resonance Energy Transfer (FRET) to sense local electric fields. Voltage sensing FRET pairs achieve voltage sensitivity up to ∼35% ΔF/F per 120 mV in cultures. Non-invasive MP recording from individual targeted sites (synapses and spines) with nanodisks has been realized. However, both of these QCSE- and FRET-based voltage nanosensors yet need to reach the milestone of recording individual action potentials from individual targeted sites.

Shear-strain-mediated photoluminescence manipulation in two-dimensional transition metal dichalcogenides

In two-dimensional transition metal dichalcogenides, normal strain can modulate electronic band structures, yet leaving the optical selection rules intact. In contrast, a shear strain can perturb the spin-valley locked band structures and possibly induce mixing of the spin subbands which in turn can transfer oscillator strength between spin-allowed bright and spin-forbidden dark excitons. Here, we report a novel scheme to manipulate photoluminescence (PL) in a monolayer WSe2-MoSe2 lateral heterostructures, controlled by an external bending method in which strong out-of-plane shear strain (OSS) of up to 5.6% accompanies weak in-plane normal strain up to 0.72%. The spectra revealed a striking dependence on the bending direction that is stagnant in the negative (compressive) strain region and then rapidly changes with increasing positive (tensile) strain. The dependency of the PL signal under tensile bending was represented not only by the large energy shift (40 meV) of the lowest excited states of both the WSe2 and MoSe2 monolayers, but also by the tendency to violate the optical selection rules that brightens (darkens) the excitons of the WSe2 (MoSe2) side. The analyses on the observed energy shifts and PL intensity changes confirm the different origins in compressive bending compared with tensile bending. The well-established band-anticrossing is identified to be affecting only the compressive deformation region. The spectral changes in the tensile region, on the other hand, originates mainly from the generation of an off-diagonal perturbation to a spin-specific Hamiltonian induced by OSS. The degree of spin-state mixing, which correlates precisely with the spin-flip coefficient of the theoretical model, is further represented by the OSS matrix elements, the spin splitting energy, and the shear deformation potential.

Accurate and Real-Time Detection Method for the Exothermic Behavior of Enzymatic Nano-Microregions Using Temperature-Sensitive Amino-AgInS2 Quantum Dots.

The thermal behavior of enzymes in nanoscale is of great significance to life phenomena. This nonequilibrium state real-time thermal behavior of enzymes at nanoscale cannot be accurately detected by existing methods. Herein, a novel method is developed for the detection of this thermal behavior. The enzyme-quantum dot (QD) conjugates can be obtained by chemically grafting temperature-sensitive amino-AgInS2 QDs to the enzyme, where the QDs act as nanothermometers with a sensitivity of -2.82%°C-1 . Detecting the photoluminescence intensity changes of the enzyme-QD conjugates, the real-time thermal behavior of enzymes can be obtained. The enzyme-QD conjugates show a temperature difference as high as 6°C above ambient temperature in nano-microregions with good reproducibility (maximum error of 4%) during catalysis, while solution temperature hardly changed. This method has a temperature resolution of ≈0.5°C with a detection limit of 0.02mgmL-1 of enzyme, and spatially ensured that the amino-AgInS2 QDs are quantitatively bound to the enzyme; thus, it can accurately detect the exothermic behavior of the enzyme and can be extended to other organisms' detection. This method has high sensitivity, good stability, and reliability, indicating its great potential application in investigating the thermal behavior of organisms in nanoscale and related life phenomena.

Innovative approaches to thermochromic materials for adaptive building envelopes

Thermochromic (TC) materials are characterized by a change of their optical response at a specific temperature. They can work based on both, the alteration of solar reflection by temperature, or the change of photoluminescence intensity. In building applications, this type of smart materials enhances the rejection of solar heat for high temperatures to favour cooling of the envelopes and reduces this rejection for low temperatures to improve surface heating. This adaptive optical response improves energy efficiency and reduces environmental impact of urban areas. Most of the current advances in this area are related to TC glazing based on Vanadium oxide, while opaque TC materials have been developed as based on Leuco dyes. The main drawback of these last materials is their significant aging in outdoor applications due to a photo-degradation process. The present work shows the recent results of a multidisciplinary and multinational consortium for research on innovative approaches to thermochromic materials for adaptive building envelopes. Next steps will be focused on building simulation to evaluate material choices across different performance aspects, while physical prototypes will be used for inter-laboratory evaluation of such performance and material durability.