Near-infrared Region Research Articles

Authentication of Coffea arabica: Comparative Multispectral Discrimination by NIR and UV–Vis Spectroscopy Aided by Artificial Neural Networks and Data Fusion

ABSTRACTCoffea arabica L. (Arabica) is considered the highest quality coffee species and provides the majority of the worldwide production. Among its groups are rare and expensive coffees; consequently, Arabica is subject to fraudulent practices. Currently, a selection of methods allow to precisely discriminate between the primary commercial coffee species (Arabica and Robusta). However, Arabica coffees offer a very restricted genetic diversity, and the authentication of its groups by spectroscopy has not yet been demonstrated to be feasible. This study aimed to step beyond the current state‐of‐the‐art, evaluating the possibility of a multispectral approach to discriminate shelf‐ready coffee beans of the most significant Arabica groups, Typica and Bourbon. Spectral analysis was performed by a benchtop near‐infrared (NIR; 1000–2500 nm), a benchtop ultraviolet–visible (UV–Vis; 200–1000 nm), and a handheld Vis‐NIR (350–2500 nm) spectrometer, hyphenated with nonlinear classification techniques, including artificial neural networks (ANNs). Additionally, low‐level (LLDF) and mid‐level (MLDF) data fusion as well as variable selection (VS) methods were evaluated in their predictive performance. This study successfully demonstrates that closely related Arabica groups are discriminable from each other using a rapid multispectral approach, including direct on‐site analysis. The NIR region provided precise classification of the Arabica coffees (94%–98% accuracy), the Vis‐NIR (88%–93 %), and the UV–Vis (82%–93 %) region showed also good discrimination but left room for improvement. However, an LLDF of the Vis‐NIR and the UV–Vis region in combination with VS proved to be a potent tool to further refine the authentication of coffee groups and showed very good classification accuracies (91%–97%).

Upconversion-Linked Immunosorbent Assay for the Biomimetic Detection of the Mycotoxin Cyclopiazonic Acid.

The neurotoxin α-cyclopiazonic acid (CPA) is an emerging mycotoxin produced as a secondary metabolite by several fungi species (i.e., Penicillium spp. and Aspergillus spp.). CPA commonly contaminates maize, crops, cheese, and wine. In this work, CPA detection in foodstuff was accomplished by the innovative integration of two strategies: upconversion nanoparticles (UCNPs) and epitope-mimicking peptides, to develop a competitive upconversion-linked immunosorbent assay (ULISA). We have applied UCNPs (type NaYF4:Yb3+, Er3+) as background-free optical labels due to their anti-Stokes shift with excitation in the near-infrared region and emission in the ultraviolet-visible region. Moreover, a CPA epitope-mimicking cyclic peptide (A2) was used as a substitute for the toxin-conjugates traditionally applied to competitive assays. UCNPs were decorated with an anti-CPA fragment antigen-binding antibody (UCNP-Fab), and CPA detection was achieved through competition with a biotinylated CPA epitope-mimicking cyclic peptide (A2-biotin, ACNWWDLTLC-GGGSK (Biotin)-NH2), anchored to a streptavidin-coated microtiter plate, for antibody binding. The ULISA platform offers ultrasensitive detection of CPA (limit of detection of 1.3 pg mL-1 and IC50 value of 15 pg mL-1), and no cross-reactivity was observed with other coproduced mycotoxins. These results substantially outperformed the analytical features of conventional heterogeneous immunoassays based on enzymatic detection. Additionally, the use of advanced computational tools, such as MOE and Alphafold AI, proved advantageous in elucidating the molecular interactions between the antibody and the epitope, providing insights that enhance the rational design of immunoassays. The proposed ULISA was applied to detect CPA in spiked maize samples, and the results were validated by high-performance liquid chromatography coupled to a tandem mass spectrometry detector (HPLC-MS/MS).

Comparative Optical Behaviour of High and Low Index Cladding Contrast Bragg Fiber

We investigate and evaluate the optical performance of high- and low-RI cladding contrast Bragg fiber for two design wavelengths: 1550 nm (in the near-infrared region) and 632.8 nm (in the visible range). In order to establish a connection between the incoming and outgoing light waves using the transfer matrix technique, the boundary matching approach is used. Less periodic cladding layers are needed to create a perfect photonic band gap (PBG), and the measured PBG in high RI cladding contrast Bragg fiber (HRCCBF) are rather large. Both low refractive index and high refractive index spectra of PBG Cladding contrast Bragg fiber (LRCCBF) performance is very sensitive to the incoming light's optical path, or angle of incidence. One way to find out how sensitive the Bragg fiber is for sensing applications is to measure the PBG's thickness or spectral shift. As the design wavelength increases, the spectral bandwidth of PBG with core RI changes, and HRCCBF seems to be quite sensitive to this shift. When taking the Left Band Edge (LBE) and the Right Band Edge (RBE) into account, LRCCBF is much more sensitive than HRCCBF, making it the better choice for sensing applications.

Portfolio of colloidally stable gold-gold sulfide nanoparticles and their use in broad-band photoacoustic imaging.

There is an increasing interest in non-invasive photoacoustic imaging and hence demand for non-toxic, stable, optical solid absorbers, particularly in the visible and near-infrared regions enabling deep tissue penetration. The most popular gold nanorods (GNR) suffer from cumbersome synthesis with poor reproducibility and stability under moderate laser exposure. Recently, a new class of nanoparticle, gold-gold sulfide (GGS), was recognized to have strong NIR absorption but lack colloidal stability. Here, we successfully synthesized a portfolio of aqueous GGS nanoparticles (NP) with excellent stability through a one-step, reproducible synthesis: Anionic, cationic, and protein-coated GGS NPs were obtained by using 3-mercaptopropionic acid (3MPA), branched poly(ethyleneimine) (bPEI) and bovine serum albumin (BSA) as a coating. All GGS NPs comprise small (<10 nm) and large anisotropic (>30 nm) morphologies and display two absorption bands centered at 530-540 nm and 800-900 nm. The photoacoustic activity (PA) of GGS NPs in solution at the visible (532 nm) and NIR (800 nm) region is similar and independent of the coating. Remarkably, they outperformed the spherical gold NPs and performed comparable to GNRs. In vitro PA microscopy images recorded with visible and NIR lasers revealed that GGS NPs are successfully internalized by triple-negative MDA-MB-231 breast cancer cells, used for the proof of principle. A coating-dependent intracellular PA signal in favor of GGS-3MPA was observed. The weakest signal was obtained with the GGS-BSA, indicating a low cellular uptake. These stable, aqueous GGS NPs emerge as promising candidates for broad-band PAI and further biomedical applications.

A Design Strategy for Low-Cost Single/Dual-Band Photodetector: Bulk Heterojunction and Interface Engineering.

Photodetectors (PDs) with band selection functions are highly desirable for the future complex environment. Currently, band-selective PDs are typically realized by integrating various optical filters with broadband PDs or constructing heterojunction with multi-photo-absorbing layers. However, these methods cause increased manufacturing costs and device integration complexity. Here, a novel solution-processed perovskite bulk heterojunction (BHJ) layer (MAPbI3:MA3Bi2I9) is developed as photo-absorbing layer, and an effective interface engineering is proposed to selectively shield photo-generated carriers in the BHJ. By regulating the bias voltage, the tunneling probability of photo-generated carrier of MAPbI3 in the BHJ layer can be easily controlled, enabling band-selective capability. The PD exhibits a superior photo-response in the visible and near-infrared region at the -0.3V, with responsivity of 26.5 and 70.2mAW-1 for 500 and 740nm, respectively. But, at the 0.1V, the PD responds only to the visible region with a photo-response of 3.7mAW-1 (500nm) and maintains a high rejection ratio (R500 nm/R740 nm) of 28.5. This PD also exhibits a fast response speed (rise time: 220µs, fall time: 240µs). This work provides a novel strategy to fabricate a cost-effective multifunctional photodetector for future advanced optoelectronic system.

Polymerized non-fullerene small molecular acceptor as a versatile electron-transport material for 24.50 % efficiency inverted perovskite solar cells with extended spectral response

Development of novel non-fullerene electron-transport materials (ETMs) with excellent optoelectronic properties, good thermal and chemical stability, and defect passivation capability is of great significance for improving the device performance of inverted perovskite solar cells (PSCs). In this work, a polymerized non-fullerene small molecular acceptor with narrow bandgap named PY-DFT is rationally designed and synthesized. The resultant materials not only exhibits great hydrophobicity, thermal and chemical stability, but also maintains the excellent electron-transport properties of Y-type small molecule. Moreover, the electron-rich units in PY-DFT finely passivates the surface defects in perovskite. Consequently, an exceptional PCE of 24.50 % has been achieved for the champion device based on PY-DFT ETM, which is the highest efficiency for inverted PSCs based on non-fullerene ETMs to date. Notably, PY-DFT provides an extra current density of 0.25 mA/cm2 in the near-infrared light response region, where the intrinsic perovskite film has no spectral response, demonstrating attractive advantages in rationally utilization of solar spectrum. The target device without encapsulation also demonstrates good long-term operational stability. This work paves a new avenue for designing photo-active non-fullerene electron-acceptor towards efficient and stable inverted PSCs.

Ni2+ in Distorted Octahedral Geometry toward High-Efficiency NIR-II/III emitter.

Ni2+ activated phosphor has attracted wide attention because it can be radiated in near-infrared (NIR) II-III region; however, the low external quantum yield (EQY) hinders its further application (most are below 8%). In this work, distortion of crystallographic site strategy is proposed to enhance EQY. LaTiTaO6: 0.004Ni2+ exhibits an NIR emitting spectrum centered at 1450 nm with an EQY of ~ 9.00%, which has been the highest EQY of reported Ni2+ single-doped phosphor. Distortion degrees of the octahedral geometry in LaTiTaO6 and LaTiTaO6: 0.004Ni2+ changing from 0.038 to 0.047 result in the absorption efficiency of 38.6% due to the breaking of parity forbidden of the d-d transition, further improving the EQY. Besides, LaTiTaO6: 0.004Ni2+ mixed with LaTiTaO6: 0.04Cr3+ phosphors have demonstrated their application for spectral analysis. This work provides a new idea for constructing efficient NIR-II to NIR-III phosphors.

Triple ultraviolet to visible perfect absorptions of lifted metamaterial for highly sensitive sensing and slow light

Achieving multiple perfect absorptions from ultraviolet (UV) to near-infrared (IR) region is practically important for metamaterial-based efficient harvesting of photons and biosensor. Here, we theoretically demonstrate a triple narrow and broad perfect absorptions (PAs) from visible to UV range in a lifted metamaterial made of aluminum vertical split-ring resonators (Al VSRR) on silica nanostrip /Al mirror. The three simultaneously achieved narrowband and broadband PAs with bandwidth of 283.3 nm, 8.9 nm and 18.2 nm are excited from magnetic plasmon resonance, surface plasmons polariton and plasmon standing wave mode, respectively, which is further explained by the impedance matching theory. The triple-band absorption peaks are further tailored by changing the size of the structure. The group index of the lifted Al VSRR array can reach as large as 2.5×103 in the UV range. Moreover, due to the designed metamaterial being lifted with the reduced substrate effect, the figure of merit (FoM*) and sensitivity (S) in the UV range are as high as 1.1×106 and 306 nm per refractive index unit‌ (306 nm/RIU), respectively. The proposed lifted metamaterial could have a considerable effect on the development of various UV plasmonic applications, including slow light nanodevices and optical sensor.

Intervalence charge transfer in aluminum oxide and aluminosilicate minerals at elevated temperatures

Abstract Single-crystal optical spectra of corundum (Al2O3) and the Al2SiO5 polymorphs andalusite, kyanite, and sillimanite, containing both Fe2+-Fe3+ and Fe2+-Ti4+ intervalence charge transfer (IVCT) absorption bands were measured at temperatures up to 1000 °C. Upon heating, thermally equilibrated IVCT bands significantly decreased in intensity and recovered fully on cooling. These trends contrast with the behavior of crystal field bands at temperature for Fe, Cr, and V in corundum, kyanite, and spinel. The effects of cation diffusion and aggregation, as well as the redistribution of band intensity at temperature, are also discussed. The loss of absorption intensity in the visible and near-infrared regions of the spectrum of these phases may point to a more general behavior of IVCT in minerals at temperatures within the Earth with implications for radiative conductivity within the Earth.

Estimating crop leaf area index and chlorophyll content using a deep learning-based hyperspectral analysis method

The crop leaf area index (LAI) and leaf chlorophyll content (LCC) are essential indicators that reflect crop growth status, and their accurate estimation is helpful for agricultural management decision-making. Traditional hyperspectral estimation methods for crop LAI and LCC from canopy spectra face challenges due to intricate soil backgrounds, canopy structural environments, and varying observational conditions. This paper proposes an LAI and LCC estimation method based on hyperspectral remote sensing, a radiation transfer model (RTM), and a leaf area index and leaf chlorophyll content deep learning network (LACNet). The LACNet architecture was developed utilizing deep and shallow feature fusion, blocks, and a hyperspectral-to-image transform (HIT) concept, aiming to improve LAI and LCC estimation. We used a field-based spectrometer to collect a dataset comprising 1,234 spectral measurements across five crop types: wheat, maize, potato, rice, and soybean. We used properties optique spectrales des feuilles and scattering by arbitrarily inclined leaves (PROSAIL) to generate a simulated spectra dataset (n = 145,152) representing complex farmland conditions for the five abovementioned crops, considering the variations in soil type, soil moisture, LAI, LCC, etc. The LACNet deep learning model sequentially uses RTM simulated and field-based spectra datasets for training, achieving higher universality and validation accuracy. We also analyzed the LACNet model’s interpretability for LAI and LCC estimation based on the gradient-weighted class activation mapping theory. From our research, we drew the following conclusions: (1) The shallow network features are sensitive to the LAI and LCC in the entire visible band, consistent with our correlation analysis results, while the deep network sensitive areas are mainly concentrated in the RE + VIS and RE + NIR regions of the HIT images. (2) The LACNet deep learning model (LAI: coefficient of determination (R2) = 0.770, root mean square error (RMSE) = 0.968 m2/m2; LCC: R2 = 0.765, RMSE = 4.547 Dualex readings) can provide higher crop LAI and LCC estimation accuracy than widely used spectral feature and statistical regression methods (LCC: R2 = 0.491–0.620, RMSE = 5.804–6.691 Dualex readings; LAI: R2 = 0.476–0.716, RMSE = 1.089–1.482 m2/m2). The results of this study highlight the potential of the LACNet deep learning model as an effective and robust tool for accurately estimating crop LAI and LCC.

Design of Near-Infrared Emissive Molecular Switches Based on Stilbene-Appended Cyclometalated Bimetallic Ru(II)-Terpyridine Complexes.

In the present study, we have synthesized and thoroughly characterized two Ru(II) dimers with compositions [(ttpy)Ru(tpvpt')Ru(ttpy)](ClO4)3 and [(ttpy)Ru(t'pvpvpt')Ru(ttpy)](ClO4)2 incorporating phenylene-vinylene-substituted terpyridine bridging ligands capable of coordinating in both an NNN- and cyclometalated NNC-fashion. The complexes display strong absorption across the entire UV-vis spectral domain and exhibit luminescence in the NIR region (820-850 nm). The N atoms in the outer coordination sphere were employed for alteration of the photoredox behaviors of the complexes via acid-base equilibria. Decoordination of the Ru-C bonds in the presence of acid, followed by recoordination in the presence of base and heat, is also possible. Additionally, the phenylene-vinylene units in the bridging ligands facilitate trans → cis and trans-trans → trans-cis isomerization under visible light irradiation. The reverse isomerization (cis → trans and trans-cis → trans-trans) is also achieved upon UV light irradiation. Thus, "on-off" and "off-on" emission switching is facilitated through a judicious choice of external stimuli like acid, base, temperature, or light of particular wavelengths. Interestingly, the rate of photoswitching is significantly faster in the presence of acid compared to that in the absence of acid. DFT and TD-DFT calculations were also conducted to clearly visualize the electronic environment around the complex backbone and also for accurate assignment of the absorption and emission bands.

Dual-Band Electrochromic Supercapacitor Utilizing Metal-Organic Coordination Polymer with Multi-Redox Feature.

Electrochromic supercapacitors, which indicate energy states through optical color changes, are gaining significant attention for their potential in energy saving and recycling. In this study, a novel metal-organic coordination polymer (DTPB-MCP) is successfully synthesized using an N,N'-diphenyl-1,4-phenylenediamine (DTPB)-functionalized phenanthroline ligand. The resulting DTPB-MCP film demonstrated desirable electrochromic performance in both the visible light (ΔT:77.6% at 730nm) and near-infrared (ΔT: 49.2% at 1410nm) regions, as well as decent energy-storage capabilities (16.4mFcm- 2 at 0.1mAcm- 2), attributed to the presence of multiple redox centers. Furthermore, a hybrid electrochromic supercapacitor is also developed by combining DTPB-MCP with V₂O₅ (DTPB-MCP//V₂O₅), showcasing a significant optical contrast (47.6% at 750nm and 14.5% at 1420nm), an acceptable capacitance of 11.5mFcm- 2 with good rate performance, and impressive cycling stability (maintaining 81% of capacitance after 2750 charging/discharging cycles). In addition, >60% of electric energy can be reused to drive small household appliances during the bleaching process. The design principles outlined in this study offer valuable insights into the development of high-performance dual-band electrochromic energy-storage materials, highlighting their potential applications in energy recovery and reuse.

Rapid and non-destructive classification of salinity levels in brined kimchi cabbage using hyperspectral imaging

In this study, we demonstrate the potential of a non-destructive hyperspectral imaging processing method in the near-infrared (NIR) region (874–1734 nm) for classifying the quality of brined kimchi cabbage. The salinity level of brined kimchi cabbage is an important indicator of consumer preference and the quality of kimchi. Hence, we compared the water content and salinity of brined kimchi cabbage via hyperspectral data. We extracted the optimal wavelengths from the hyperspectral image dataset to classify the salinity level of the predicted brined kimchi cabbage, and thus, established a novel approach for classifying kimchi samples into quality-unacceptable and quality-acceptable groups. Standard normal variate and multiplicative scatter correction (MSC) were used for pathlength correction. The Savitzky–Golay first and second derivatives were used for the deconvolution of the raw spectral data. The experimental results confirmed that the decision tree model combined with MSC pathlength correction and Savitzky–Golay first derivative preprocessing was the best classification model. The proposed hyperspectral image–NIR system can be applied to the detection of salinity during industrial kimchi manufacturing.

Carrier-free porphyrin-based supramolecular complexes for near-infrared photothermal-enhanced wound healing

Inspired by the assembly of biological macromolecules, supramolecular chemistry has been used to develop various biofunctional mateirals. For example, charge-transfer complexes (CTCs) are recently engineered for photothermal conversion in the near-infrared (NIR) region. Most CTCs rely on surfactants to enhance their dispersity and stability in water, but the potential toxicity associated with surfactants may limit further development of CTCs in biomedical field. Herein, we constructed carrier-free CTCs (TAPP/PDI-G NPs) by selecting 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) as the electron donor and perylenediimide derivative (PDI-G) as the acceptor. TAPP/PDI-G NPs exhibit a NIR absorption peak at 758 nm, significantly longer than that of individual TAPP or PDI-G. Moreover, upon irradiation with an 808 nm laser, TAPP/PDI-G NPs exert exceptional photothermal performance and display efficient antibacterial properties both in vitro and in vivo. The proposed strategy highlights the great potential of supramolecular assembly in constructing desirable materials.

A unique cuvette and near-infrared spectral imaging for fast and accurate quantification of milk compositions

Analyzing the nutritional compositions of milk using traditional methods is costly, time-consuming, and impractical for rapid field measurements, resulting in delays in quality control procedures. This paper presents a rapid, accurate, and easy-to-use method for quantitative analysis of finished milk compositions using a low-cost, portable, and environmentally friendly measurement system. The system uses a near-infrared (NIR) broadband digital camera to capture spectral images of milk after it is placed in a customized cuvette in the short-wave NIR region (700–1050 nm). A machine learning algorithm that combines image edge detection and gradient-boosted decision trees then regresses these images to predict the protein and fat content of the milk. Each measurement requires a maximum of 1.75 mL of milk sample with no additional consumables and takes 0.1 s to complete. The coefficient of determination (R2CV) for the fat detection model was 0.999 and the root mean square error (RMSECV) was 0.026 g/100 mL. For protein detection, the R2CV was 0.957 and the RMSECV was 0.058 g/100 mL. The experimental results show that the system achieves high precision and stability while realizing miniaturization and portability.

Multifunctional Optical Sensor for the Comprehensive Detection of Zinc Ions in Cardiovascular Disease.

Cardiovascular diseases (CVDs) are a major global health concern, highlighting the need for effective diagnostic tools. Zinc ions (Zn2+) play a role in CVDs, but their detection is challenging. This study presents a multifunctional optical sensor, HD-Zn, designed to detect Zn2+ in relation to CVDs. We developed a novel fluorescence probe, HD-Zn, by conjugating N,N-di(2-picolyl)ethylenediamine (DPEN) to HD via an amide bond, which results in fluorescence quenching due to photoinduced electron transfer (PeT). Adding Zn2+ significantly increased fluorescence intensity in the near-infrared region (NIR-I). The probe showed a linear response to varying Zn2+ concentrations, with a detection limit of 9.8 nM, appropriate for physiological conditions. Fluorescence imaging in RAW264.7 macrophages indicated lower intracellular Zn2+ levels in foam cells compared to healthy cells, linked to CVDsprogression. In vivo imaging in mouse models showed decreased fluorescence intensity in the aorta with disease progression. Our findings confirm that HD-Zn is a reliable tool for measuring Zn2+ levels in plaques and demonstrate its biosafety for detecting Zn2+ in serum and urine, offering potential for clinical applications in CVDs diagnosis and monitoring.

Introducing of an Unexplored Aza-BODIPY Diradicaloids with 4-(2,6-Ditert-butyl)phenoxyl Radicals Located in 1,7-Positions of the Aza-BODIPY Core.

We have prepared and characterized two diradicaloid systems 5a and 5b that originated from the oxidation of a 1,7-(4-(2,6-di-tert-butyl)phenol)-substituted aza-BODIPY core. The aza-BODIPY diradicaloids were characterized by a large array of experimental and computational methods. The diamagnetic closed-shell state was postulated as the ground state in solution and a solid-state with the substantial thermal population originating from both open-shell diradical and open-shell triplet states observed at room temperature. Transient absorption spectroscopy indicates fast (<10 ps) excited state deactivation pathways associated with the target compounds' diradical character in solution at room temperature. Variable-temperature 1H NMR spectra indicate the solvent dependency of the diradical character in 5a and 5b. The diradicaloids could be stepwise reduced to the mixed-valence radical-anion and dianion states upon consequent single-electron reductions. Similarly, deprotonated 1,7-(4-(2,6-di-tert-butyl)phenol)-substituted aza-BODIPYs can be oxidized to the diradicaloid form. Both mixed-valence and dianionic forms exhibit an intense absorption in the NIR region. Density functional theory (DFT) and time-dependent DFT calculations were used to explain the transformations in the UV-Vis-NIR spectra of all target compounds.

Enhanced light extraction by optimizing near-infrared perovskite-based light emitting diode (PeLED)

One of the outstanding optoelectronic devices is perovskite-based light emitting diodes (PeLEDs) that have diverse applications according to the wavelength of produced light. However, these devices have shown more than 20% External Quantum Efficiency (EQE), in comparison with their counterparts (OLEDs), light extraction is limited in these devices. In this paper, by optimizing the thickness of layers and manipulating absorption in the active layer (AL), the light extraction efficiency (LEE) increased by nearly 20%. It reached 42.89% in the near-infrared (NIR) region of the wavelength, by considering the CH(NH2)2PbI3 perovskite, in the emissive layer (EML).

A multiband NIR upconversion core-shell design for enhanced light harvesting of silicon solar cells

Exploring lanthanide light upconversion (UC) has emerged as a promising strategy to enhance the near-infrared (NIR) responsive region of silicon solar cells (SSCs). However, its practical application under normal sunlight conditions has been hindered by the narrow NIR excitation bandwidth and the low UC efficiency of conventional materials. Here, we report the design of an efficient multiband UC system based on Ln3+/Yb3+-doped core-shell upconversion nanoparticles (Ln/Yb-UCNPs, Ln3+ = Ho3+, Er3+, Tm3+). In our design, Ln3+ ions are incorporated into distinct layers of Ln/Yb-UCNPs to function as near-infrared (NIR) absorbers across different spectral ranges. This design achieves broad multiband absorption withtin the 1100 to 2200 nm range, with an aggregated bandwidth of ~500 nm. We have identified a synthetic electron pumping (SEP) effect involving Yb3+ ions, facilitated by the synergistic interplay of energy transfer and cross-relaxation between Yb3+ and other ions Ln3+ (Ho3+, Er3+, Tm3+). This SEP effect enhances the UC efficiency of the nanomaterials by effectively transferring electrons from the low-excited states of Ln3+ to the excited state of Yb3+, resulting in intense Yb3+ luminescence at ~980 nm within the optimal response region for SSCs, thus markedly improving their overall performance. The SSCs integrated with Ln/Yb-UCNPs with multiband excitation demonstrate the largest reported NIR response range up to 2200 nm, while enabling the highest improvement in absolute photovoltaic efficiency reported, with an increase of 0.87% (resulting in a total efficiency of 19.37%) under standard AM 1.5 G irradiation. Our work tackles the bottlenecks in UCNP-coupled SSCs and introduces a viable approach to extend the NIR response of SSCs.

Janus Photothermal Films with Orientated Plasmonic Particle-in-Cavity Surfaces Enabling Heat Control in Solar-Thermal-Electric Generators.

Solar thermoelectric generators (STEGs) consisting of solar absorbers and thermoelectric generators (TEGs) can utilize solar energy to generate electrical power. However, performances of STEGs are limited by the heat losses of solar absorbers in air, which become more and more significant with an increase in the solar absorbing area. Herein, we describe the preparation of Au@AgPd nanostructure monolayer/poly(vinyl alcohol) (PVA) Janus photothermal films with broadband plasmonic absorption in the visible and near-infrared regions. By uniaxially stretching the Janus film, Au@AgPd can align along the stretching direction, which creates particle-in-cavity structures on the PVA surface. Benefiting from the oriented plasmonic particle-in-cavity configuration, the Janus films effectively convert sunlight into heat, trap the heat within their micrometer-depth structure, and facilitate its transfer along the direction of the nanostructure orientation. Integration of the Janus films with commercial TEGs allows thermal concentration onto a small thermoelectric surface, yielding an open-circuit voltage of 308 mV under 102 mW/cm2 natural sunlight illumination. Heat losses in commercial TEGs integrated with Janus films are reduced by approximately 50% while maintaining the same voltage output. Furthermore, incorporating the Janus films into a conventional STEG with carbon-based solar absorbers significantly enhances solar-thermal-electric conversion performance, achieving an output power density of 1.3 W m-2. Our design of Janus photothermal films with oriented particle-in-cavity surfaces can be extended to various solar-thermal systems for high-efficiency solar energy conversion and heat management.