Near-infrared Applications Research Articles

Influence of Bi+ ions on photoluminescence properties of Tm2O3 doped borotellurite glasses for the near-infrared emission applications

This paper reports the influence of bismuth ions (Bi+) on photoluminescence properties of Tm2O3 doped borotellurite based glasses (BTGS) with the composition (64-y)B2O3–30TeO2 – 5NaF- yBi2O3–1Tm2O3, where y = 0, 4, 8, 12 and 16 wt% for the near-infrared (NIR) emission applications. All glasses were prepared using the melt-quenching method and confirmed to exhibit amorphous nature by the X-ray diffraction (XRD) technique. The absorption spectra in the wavelength range of 300–2100 nm and emission spectra in the wavelength range of 400–2200 nm were studied. Increase of y wt. % value increases the 3H4→3F4 and 3F4→3H6 (near-infrared, NIR emission) intensities due to cross-relaxation (CR) and enhanced energy transfer processes between the active centres (Bi+ and Tm3+ ions), which are strongly influenced by bismuth content (Bi+) in the glass matrix. Based on Judd-Ofelt theory, the intensity parameters Ω2, Ω4 and Ω6 for each glass were determined and found to follow the trend Ω2>Ω4>Ω6 similar to the recently reported photonic glasses. Using the Ωλ parameters and reduced matrix elements, the calculation for the emission transition probability (A), radiative lifetime (τR), branching ratio (βR) and emission-cross sections (σPE) of 3H4, 3H5, and 3F4 energy levels were done and found to be slightly higher than fluoride and other oxide-based glasses because of the high density and refractive index values of the present samples.

Near-infrared light-emitting diodes based on Tm-doped Ga2O3

Near-infrared (NIR) light-emitting diodes (LEDs) based on Tm–Ga2O3/GaAs were fabricated by pulsed laser deposition. The strongest NIR emission observed at 794 nm can be assigned to the 3H4–3H6 transition. The major blue emission detected at 476 nm can be attributed to the 1G4-3H6 transition. The turn-on voltage of 794 nm emission is 5.5 V lower than 6.9 V for 476 nm emission. The ratio of the 794 to 476 nm emission intensities of Tm–Ga2O3/GaAs LEDs is close to a constant of 11.4. These results open a pathway for Ga2O3 based LEDs used in NIR application.

Three dimensional fluorene-based polyamides facile to transfer ion designed for near-infrared electrochromic application and detection for explosive

Near-infrared electrochromic (NIR EC) functional materials are attracting increasing attention owing to their great potential for applications in smart window. However, obtaining high performance NIR EC material with high optical transmittance contrast, fast redox switching and long-term cyclic stability is still a challenge. Introducing four triphenylamine (TPA) units into one planar fluorene core to build robust three dimensional (3D) framework which not only makes ion and electron move freely but also provides sufficient space and storage sites for hosting ions will meet the requirement. Here, three kinds of new polyamides (PAs) based on conjugated fluorene as the bridge unit were designed and polycondensized by a new diamine N, N'-(9,9-bis(4-(diphenylamino)phenyl)-9H-fluorene-2,7-diyl)-bis(N-(4-methoxyphenyl) benzene-1,4-diamine), with three kinds of dicarboxylic acids to form TPAF-6F, TPAF-CA and TPAF-OA. The obtained new PAs exhibit impressive solution-processability and excellent thermal stability. Cyclic voltammograms (CV) and differential pulse voltammograms (DPV) of the PAs imply strong electronic coupling within molecule. Furthermore, the TPAF-OA film exhibits excellent EC performance with multi-coloured EC behaviour, high optical contrast (92%), high coloration efficiency (203 cm2 C−1) and outstanding cycle stability (optical contrast remains 90% over 1400 cycles) in the NIR range. TPAF-CA also shows impressive fluorescence (PL) quantum efficiency which could be used as sensor for explosive and nonvolatile flash memory properties. The strategy of introducing 3D framework block into polymer will pave a way for fabricating high performance optoelectronic devices.

Application of NIRs coupled with PLS and ANN modelling to predict average droplet size in oil-in-water emulsions prepared with different microfluidic devices

In this study, the potential of microfluidic systems with different microchannel geometries (microchannel with teardrop micromixers and microchannel with swirl micromixers) for the preparation of oil-in-water (O/W) emulsions using two different emulsifiers (2 % and 4 % Tween 20 and 2% and 4 % PEG 2000) at total flow rates of 20–280 μL/min was investigated. The results showed that droplets with a smaller average Feret diameter were obtained when a microfluidic device with tear drop micromixers was used. To predict the average Feret diameter of O/W emulsion droplets, near-infrared (NIR) spectra of all prepared emulsions were collected and coupled with partial least squares (PLS) regression and artificial neural network modelling (ANN). The results showed that PLS models based on NIR spectra can ensure acceptable qualitative prediction, while highly non-linear ANN models are more suitable for predicting the average Feret diameter of O/W droplets. High R2 values (R2validation greater than 0.8) confirm that ANNs can be used to monitor the emulsification process.

Advancing Near-Infrared Phosphorescence with Heteroleptic Iridium Complexes Bearing a Single Emitting Ligand: Properties and Organic Light-Emitting Diode Applications

Cyclometalated iridium complexes, emitters of choice in organic light-emitting diodes (OLEDs), hold great potential for near-infrared (NIR) applications. Upon increasing the conjugation size and chemical complexity of the ligands, as required to push the emission toward the NIR), overall high-molecular-weight complexes (both homoleptic and heteroleptic β-diketonate ones) are obtained, posing related issues in OLED processing. One, so far barely explored, question arises: “Why endow Ir(III) with three or two emissive ligands when one might work just as well?” Herein, as proof of concept for OLED technology, we disclose three novel deep-red to NIR emitters of formula Ir(C^N)2(iqbt), with a single iqbt (1-(benzo[b]thiophen-2-yl)-isoquinolinate) ligand responsible for the emission in the NIR range. (C^N) are cyclometalated ligands with higher triplet energy than that of iqbt. We demonstrate that the presence of a single iqbt ligand is sufficient to enable efficient phosphorescence matching that of homoleptic Ir(iqbt)3; moreover, the Ir(C^N)2(iqbt) based OLEDs display efficiency exceeding the one of Ir(iqbt)3. These compounds offer several important benefits: (i) advantageous synthetic protocols limiting to the last step of the use of novel and synthetic costly NIR ligands (implying a lower amount of ligand required), (ii) commercially available (C^N) to prepare the starting Ir chloro-dimers, and (iii) lower molecular weight of the complexes compared to that of the homoleptic parent ones fruitful for easier vacuum thermal processing of the emitters.

Cr3+-doped borate phosphors for broadband near-infrared LED applications

A novel broadband NIR phosphor K6Li0.9Na0.1CaSc2(B5O10)3:Cr3+ with a single luminescence center has been successfully synthesized, and the relationship between the crystal structure and the luminescence properties was systematically investigated.

Synthesis of Thieno[3,4-b]pyrazine-based Alternating Conjugated Polymers via Direct Arylation for Near-infrared OLED Applications

Synthesis of Thieno[3,4-b]pyrazine-based Alternating Conjugated Polymers via Direct Arylation for Near-infrared OLED Applications

The Near-Infrared Luminescence Properties and Applications of Ca3lu2ge3o12: Cr3+ Phosphor

The Near-Infrared Luminescence Properties and Applications of Ca3lu2ge3o12: Cr3+ Phosphor

Effects of nanoaggregation on isoindigo-based fluorophores for near-infrared bioimaging applications

This work provides fascinating insights into NIR fluorophore design and methods to effectively alter the photophysical and morphological properties of the nanoaggregates for bio-imaging purposes.

Band structure tuning of g-C3N4 via sulfur doping for broadband near-infrared ultrafast photonic applications.

Graphitic carbon nitride (g-C3N4) featuring a stable heptazine ring structure and high polymerization degree, was indexed as a high thermochemical stability material, attracting rising research enthusiasm for diverse applications. However, the poor near-infrared (NIR) optical absorption and resulting limited NIR applications were pronounced for g-C3N4 due to its large bandgap of 2.7eV. In the present work, sulfur-doping was manifested by first-principles calculations to introduce impurity level and result in anisotropic spin splitting in g-C3N4 for enhancing broadband nonlinear optical characteristics in NIR regime. The modified sulfur-doped g-C3N4 (S-C3N4) exhibited the maximum effective nonlinear absorption coefficient to be-0.82cm/GW. Pulse duration within hundred nanoseconds was realized with high modulation stability employing S-C3N4 as saturable absorber in Q-switching operations. Moreover, broadband ultrafast photonics properties were successfully demonstrated in constructed ytterbium-doped and erbium-doped fiber lasers, generating highly stable dissipative soliton and traditional soliton mode-locking pulses. The presented S-C3N4 nanomaterial with remarkable nonlinear optical performances might explicitly boost the development and application of g-C3N4 materials in advanced optoelectronic and ultrafast photonic devices.

Investigation on multifunctional binary oxides for near-infrared (NIR) reflective pigment applications

Investigation on multifunctional binary oxides for near-infrared (NIR) reflective pigment applications

Efficient Broadband Near‐Infrared Emission in the GaTaO4:Cr3+ Phosphor

AbstractEfficient broadband near‐infrared (NIR) emitting materials with an emission peak centered above 830 nm are crucial for smart NIR spectroscopy‐based technologies. However, the development of these materials remains a significant challenge. Herein, a series of design rules rooted in computational methods and empirical crystal‐chemical analysis is applied to identify a new Cr3+‐substituted phosphor. The compound GaTaO4:Cr3+ emerged from this study is based on the material's high structural rigidity, suitable electronic environment, and relatively weak electron–phonon coupling. Irradiating this new phosphor with 460 nm blue light generates a broadband NIR emission (λem,max = 840 nm) covering the 700–1100 nm region of the electromagnetic spectrum with a full width at half maximum of 140 nm. The phase has a high internal quantum yield of 91% and excellent thermal stability, maintaining 85% of the room temperature emission intensity at 100 °C. Fabricating a phosphor‐converted light‐emitting diode device shows that the new compound generates an intense NIR emission (178 mW at 500 mA) with photoelectric efficiency of 6%. This work not only provides a new material that has the potential for next‐generation high‐power NIR applications but also highlights a set of design rules capable of developing highly efficient long‐wavelength broadband NIR materials.

Room-Temperature Direct Synthesis of PbSe Quantum Dot Inks for High-Detectivity Near-Infrared Photodetectors.

A PbSe colloidal quantum dot (QD) is typically a solution-processed semiconductor for near-infrared (NIR) optoelectronic applications. However, the wide application of PbSe QDs has been restricted due to their instability, which requires tedious synthesis and complicated treatments before being applied in devices. Here, we demonstrate efficient NIR photodetectors based on the room-temperature, direct synthesis of semiconducting PbSe QD inks. The in-situ passivation and the avoidance of ligand exchange endow PbSe QD photodetectors with high efficiency and low cost. By further constructing the PbSe QDs/ZnO heterostructure, the photodetectors exhibit the NIR responsivity up to 970 mA/W and a detectivity of 1.86 × 1011 Jones at 808 nm. The obtained performance is comparable to that of the state-of-the-art PbSe QD photodetectors using a complex ligand exchange strategy. Our work may pave a new way for fabricating efficient and low-cost colloidal QD photodetectors.

Self-powered and broadband germanium/PEDOT:PSS heterojunction photodetectors for near-infrared biomedical imaging applications

Self-powered and broadband germanium/PEDOT:PSS heterojunction photodetectors for near-infrared biomedical imaging applications

Recent Advances in Portable and Handheld NIR Spectrometers and Applications in Milk, Cheese and Dairy Powders.

Quality and safety monitoring in the dairy industry is required to ensure products meet a high-standard based on legislation and customer requirements. The need for non-destructive, low-cost and user-friendly process analytical technologies, targeted at operators (as the end-users) for routine product inspections is increasing. In recent years, the development and advances in sensing technologies have led to miniaturisation of near infrared (NIR) spectrometers to a new era. The new generation of miniaturised NIR analysers are designed as compact, small and lightweight devices with a low cost, providing a strong capability for on-site or on-farm product measurements. Applying portable and handheld NIR spectrometers in the dairy sector is increasing; however, little information is currently available on these applications and instrument performance. As a result, this review focuses on recent developments of handheld and portable NIR devices and its latest applications in the field of dairy, including chemical composition, on-site quality detection, and safety assurance (i.e., adulteration) in milk, cheese and dairy powders. Comparison of model performance between handheld and bench-top NIR spectrometers is also given. Lastly, challenges of current handheld/portable devices and future trends on implementing these devices in the dairy sector is discussed.

PbS Quantum Dots Saturable Absorber for Dual-Wavelength Solitons Generation.

PbS quantum dots (QDs), a representative zero-dimensional material, have attracted great interest due to their unique optical, electronic, and chemical characteristics. Compared to one- and two-dimensional materials, PbS QDs possess strong absorption and an adjustable bandgap, which are particularly fascinating in near-infrared applications. Here, fiber-based PbS QDs as a saturable absorber (SA) are studied for dual-wavelength ultrafast pulses generation for the first time to our knowledge. By introducing PbS QDs SA into an erbium-doped fiber laser, the laser can simultaneously generate dual-wavelength conventional solitons with central wavelengths of 1532 and 1559 nm and 3 dB bandwidths of 2.8 and 2.5 nm, respectively. The results show that PbS QDs as broadband SAs have potential application prospects for the generation of ultrafast lasers.

Structure and Luminescence Properties of Transparent Germanate Glass-Ceramics Co-Doped with Ni2+/Er3+ for Near-Infrared Optical Fiber Application.

An investigation of the structural and luminescent properties of the transparent germanate glass-ceramics co-doped with Ni2+/Er3+ for near-infrared optical fiber applications was presented. Modification of germanate glasses with 10–20 ZnO (mol.%) was focused to propose the additional heat treatment process controlled at 650 °C to obtain transparent glass-ceramics. The formation of 11 nm ZnGa2O4 nanocrystals was confirmed by the X-ray diffraction (XRD) method. It followed the glass network changes analyzed in detail (MIR—Mid Infrared spectroscopy) with an increasing heating time of precursor glass. The broadband 1000–1650 nm luminescence (λexc = 808 nm) was obtained as a result of Ni2+: 3T2(3F) → 3A2(3F) octahedral Ni2+ ions and Er3+: 4I13/2 → 4I15/2 radiative transitions and energy transfer from Ni2+ to Er3+ with the efficiency of 19%. Elaborated glass–nanocrystalline material is a very promising candidate for use as a core of broadband luminescence optical fibers.

Intraoperative detection of parathyroid glands by autofluorescence identification using image-based system: report of 15 cases

BackgroundA detection of parathyroid glands by the evaluation of their autofluorescence in the near-infrared spectrum is considered as a promising tool in addition to their visual verification. The aim of this study was to evaluate the role of near-infrared autofluorescence application by using two different image-based systems for the identification of parathyroid glands during surgery of thyroid and parathyroid benign and malignant lesions.MethodsEvaluation of near-infrared autofluorescence was performed in 15 patients by using two different image-based systems equipped with a near-infrared laser camera. Intravenous injection of fluorophore indocyanine green was used for the enhancement of near-infrared autofluorescence signal.ResultsNormal parathyroid glands were identified and mobilized after visual inspection in 12 (80%) patients, which was confirmed by near-infrared autofluorescence evaluation. Confident recognition of parathyroid glands by near-infrared autofluorescence signal and their subsequent distinction from lymph nodes was achieved in two (13%) patients with prior surgery for papillary thyroid carcinoma. In one (7%) case, parathyroid gland was identified as fragments of tissue within the postoperative scarring area by near-infrared autofluorescence evaluation, but not by visual inspection. A less intensive near-infrared autofluorescence signal was detected in the parathyroid gland owing to unintentional excision in one (7%) case. Better signal intensity from parathyroid glands was noticed after changes of the near-infrared camera in Fluobeam 800 image-based system in position to an angle of approximately 45–65° in relation to area of interest in all cases as compared with holding straight on the parathyroid gland. Fluobeam LX demonstrated a good near-infrared autofluorescence signal without any specific changes in the camera angle. Thyroid carcinoma demonstrated low-intensity signal in the case of invasion to thyroid capsule. No fluorescent signal was identified from metastatic, or from normal, lymph nodes.ConclusionsThe application of near-infrared autofluorescence imaging is considered as a useful, but additional, tool for the visual assessment of parathyroid gland in the case of primary neck exploration. The utility of near-infrared autofluorescence imaging for parathyroid detection is increased in the case of repeated surgical intervention owing to increased risk of unintentional parathyroid removal as well as for discrimination of parathyroids from the lymph nodes in cases of thyroid malignancy.

Spectroscopic analysis of Nd3+-doped cadmium-vanadate invert glasses for near-infrared laser applications

Nd3+ activated CdO-V2O5 invert glasses were synthesized by the well-stablished melt quenching technique, using starting proportions of 95.0 and 5.0 mol% of CdO and V2O5, respectively. The XRD patterns revealed that the glass system remains amorphous up to 4.0 mol% of Nd3+. Such fact was mainly attributed to the low V2O5 content, which avoided the segregation of additional phases. The minimal addition of 0.1 mol% of Nd3+ reduced the direct and indirect glass bandgap energies from 2.79 to 2.66 eV, and from 2.48 to 2.13 eV, respectively. For higher Nd3+ contents, the bandgap energy was recovered, reaching values of 2.78 and 2.40 eV for direct and indirect allowed transitions, respectively. This fact was associated with a Burstein-Moss like effect, observed in semiconductors highly doped. The tail of the absorption edge revealed that the Urbach energy systematically grows with the addition of Nd3+, because of the creation of localized states into the bandgap. The Judd-Ofelt (JO) parameters obtained by least-square method from the experimental and theoretical oscillator strengths, were found in the Ω2 = 5.24-11.04 × 10−20 cm2, Ω4 = 2.26-4.47 × 10−20 cm2, and Ω6 = 2.85-6.28 × 10−20 cm2 range. Such values are close to those reported in other popular glass systems. The stimulated emission cross-section peak (σp) values calculated for the glass sample doped with 2.0 mol% resulted to be 0.26 × 10−20 cm2 (Nd3+: 4F3/2 → 4I9/2) and 0.81 × 10−20 cm2 (Nd3+: 4F3/2 → 4I11/2). The Nd3+ emission spectra, recorded upon 585 nm excitation (Nd3+: 4I9/2 → 4G5/2 + 2G7/2), showed the near-infrared Nd3+ emission bands at 881 nm (Nd3+: 4F3/2 → 4I9/2), 1063 nm (Nd3+: 4F3/2 → 4I11/2) and 1341 nm (Nd3+: 4F3/2 → 4I13/2), being dominated for that coming from the Nd3+: 4F3/2 → 4I11/2 transition. The overall emission reached the optimum intensity at 2.0 mol% of Nd3+, with a maximum quantum efficiency (ηQE) of 0.23. From the emission spectra important laser parameters such as gain bandwidth (σEMI(λp) × Δλem) and optical gain (σEMI(λp) × τR), were determined for the sample with the highest ηQE value. The σEMI(λp) × Δλem values resulted to be 11.3 and 32.0 × 10−27 cm3 for the Nd3+: 4F3/2 → 4I9/2, 11/2 transitions, respectively. The σEMI(λp) × τR parameter values were 11.1 and 35.3 × 10−25 cm2s for Nd3+: 4F3/2 → 4I9/2,11/2 transitions, respectively. The Inokuti-Hirayama model suggested that the Nd3+ cross-relaxation process might be dominated by an electric dipole-dipole interaction, inside Nd3+-Nd3+ clusters.

Alkali metal tungsten bronze-doped energy-saving glasses for near-infrared shielding applications

Tungsten bronze has attracted global attention for its applications in near-infrared (NIR)-shielding windows. Here, alkali metal tungsten bronze (MxWO3, M = one or two types of Li, Na, and K)-doped glasses are prepared by a simple melt-quenching method. Their structure and properties were characterized by XRD, Raman spectroscopy, XPS and UV–Vis–NIR spectrophotometry. The effects of M on their structure and the NIR shielding performance are investigated. The LiF sample has the best NIR shielding performance, but its visible transmittance is sacrificed due to its low quality. The glasses containing mixed Li+ and K+ cooperate to form a high-quality Li+/K+-codoped tungsten bronze, while the glasses containing mixed Li+ and Na+ compete for limited tungsten resources to form Li+- and Na+-doped tungsten bronzes separately. The research here is helpful for understanding the role of different alkali metal ions in bulk energy-saving glass and is hugely significant for the guidance of the future applications of energy-saving glass without films.