Near-infrared Response Research Articles

Comparison of Dopant Incorporation and Near-Infrared Photoresponse for Se-Doped Silicon Fabricated by fs Laser and ps Laser Irradiation

Se-doped silicon films were fabricated by femtosecond (fs) laser and picosecond (ps) laser irradiating Si–Se bilayer film-coated silicon. The surface morphology, impurity distribution, crystal phase, and near-infrared photocurrent response of fs-laser-processed and ps-laser-processed Si are compared. With the same number of laser pulse irradiation, fs laser induces quasi-ordered micron-size columnar structures with some deeper gullies, and ps laser induces irregular nanoscale spherical particles with some cavities. Compared with the fs-laser-produced Se-doped layer, ps laser irradiation produces a Se-doped layer with better crystallinity and higher doping concentration, resulting in a higher photocurrent response for picosecond laser-processed Si in the near-infrared band. The changes brought about by ps laser processing facilitate the application of ultrafast laser-processed chalcogen-doped silicon for silicon-based integrated circuits.

Towards highly efficient NIR II response up-conversion phosphor enabled by long lifetimes of Er3+

The second near-infrared (NIR II) response photon up-conversion (UC) materials show great application prospects in the fields of biology and optical communication. However, it is still an enormous challenge to obtain efficient NIR II response materials. Herein, we develop a series of Er3+ doped ternary sulfides phosphors with highly efficient UC emissions under 1532 nm irradiation. β-NaYS2:Er3+ achieves a visible UC efficiency as high as 2.6%, along with high brightness, spectral stability of lights illumination and temperature. Such efficient UC is dominated by excited state absorption, accompanied by the advantage of long lifetimes (4I9/2, 9.24 ms; 4I13/2, 30.27 ms) of excited state levels of Er3+, instead of the well-recognized energy transfer UC between sensitizer and activator. NaYS2:Er3+ phosphors are further developed for high-performance underwater communication and narrowband NIR photodetectors. Our findings suggest a novel approach for developing NIR II response UC materials, and simulate new applications, eg., simultaneous NIR and visible optical communication.

A metal-organic framework nanocomposite with oxidation and near-infrared light cascade response for bacterial photothermal inactivation.

Photothermal treatment is an effective and precise bacterial disinfection method that can reduce the occurrence of bacterial drug resistance. However, most conventional photothermal treatment strategies have the problem that the photothermal response range does not match the infection area. Herein, a metal-organic framework (MOF) nanocomposite responding to the oxidation state of the bacterial infection microenvironment was constructed for near-infrared (NIR) photothermal bacterial inactivation. In this strategy, the MOF was used as a nanocarrier to load tetramethylbenzidine (TMB) and horseradish peroxidase (HPR). The high oxidation state of the bacterial infection microenvironment can trigger the enzyme-catalyzed reaction of the nanocomposite, thereby generating oxidation products with the NIR photothermal effect for bacterial disinfection. The synthesis and characterization of the nanocomposite, oxidation state (H2O2) response effect, photothermal properties, and antibacterial activities were systematically studied. This study provides a new idea for building a precision treatment system for bacterial infection.

Recent Developments in Heterogeneous Photocatalysts with Near-Infrared Response

Photocatalytic technology has been considered as an efficient protocol to drive chemical reactions in a sustainable and green way. With the assistance of semiconductor-based materials, heterogeneous photocatalysis converts solar energy directly into chemical energy that can be readily stored. It has been employed in several fields including CO2 reduction, H2O splitting, and organic synthesis. Given that near-infrared (NIR) light occupies 47% of sunlight, photocatalytic systems with a NIR response are gaining more and more attention. To enhance the solar-to-chemical conversion efficiency, precise regulation of the symmetric/asymmetric nanostructures and band structures of NIR-response photocatalysts is indispensable. Under the irradiation of NIR light, the symmetric nano-morphologies (e.g., rod-like core-shell shape), asymmetric electronic structures (e.g., defect levels in band gap) and asymmetric heterojunctions (e.g., PN junctions, semiconductor-metal or semiconductor-dye composites) of designed photocatalytic systems play key roles in promoting the light absorption, the separation of electron/hole pairs, the transport of charge carriers to the surface, or the rate of surface photocatalytic reactions. This review will comprehensively analyze the four main synthesis protocols for the fabrication of NIR-response photocatalysts with improved reaction performance. The design methods involve bandgap engineering for the direct utilization of NIR photoenergy, the up-conversion of NIR light into ultraviolet/visible light, and the photothermal effect by converting NIR photons into local heat. Additionally, challenges and perspectives for the further development of heterogeneous photocatalysts with NIR response are also discussed based on their potential applications.

Spatial distribution as a key factor for evaluation of soil attributes prediction at field level using online near-infrared spectroscopy

In soil science, near-infrared (NIR) spectra are being largely tested to acquire data directly in the field. Machine learning (ML) models using these spectra can be calibrated, adding only samples from one field or gathering different areas to augment the data inserted and enhance the models’ accuracy. Robustness assessment of prediction models usually rely on statistical metrics. However, how the spatial distribution of predicted soil attributes can be affected is still little explored, despite the fact that agriculture productive decisions depend on the spatial variability of these attributes. The objective of this study was to use online NIR spectra to predict soil attributes at field level, evaluating the statistical metrics and also the spatial distribution observed in prediction to compare a local prediction model with models that gathered samples from other areas. A total of 383 online NIR spectra were acquired in an experimental field to predict clay, sand, organic matter (OM), cation exchange capacity (CEC), potassium (K), calcium (Ca), and magnesium (Mg). To build ML calibrations, 72 soil spectra from the experimental field (local dataset) were gathered, with 59 samples from another area nearby, in the same geological region (geological dataset) and with this area nearby and more 60 samples from another area in a different region (global dataset). Principal components regression was performed using k-fold (k=10) cross-validation. Clay models reported similar errors of prediction, and although the local model presented a lower R2 (0.17), the spatial distribution of prediction proved that the models had similar performance. Although OM patterns were comparable between the three datasets, local prediction, with the lower R2 (0.75), was the best fitted. However, for secondary NIR response attributes, only CEC could be successfully predicted and only using local dataset, since the statistical metrics were compatible, but the geological and global models misrepresented the spatial patterns in the field. Agronomic plausibility of spatial distribution proved to be a key factor for the evaluation of soil attributes prediction at field level. Results suggest that local calibrations are the best recommendation for diffuse reflectance spectroscopy NIR prediction of soil attributes and that statistical metrics alone can mispresent the accuracy of prediction.

Near-Infrared Turn-On Fluorescent Probe for Aqueous Fluoride Ion Detection and Cell Imaging.

Fluoride ions are one of the most essential anions in the human body and have been implicated in various pathological and physiological processes. The detection of fluoride ions in aqueous solution, as well as the imaging of fluoride ions in living cells, remains a challenge. We herein report a BODIPY-based fluorescent probe employing a pinacol borate group as the recognition moiety for the detection of fluoride ions in aqueous solutions. This probe shows high selectivity and sensitivity to fluoride ions with a significant near-infrared fluorescence turn-on response. In addition, this probe was successfully employed in fluorescence bioimaging of fluoride ions in the human cervical cancer cell and mouse mammary cancer cell, demonstrating its good cell permeability and stability under physiological conditions.

Near-Infrared Liposome-Capped Au-Rare Earth Bimetallic Nanoclusters for Fluorescence Imaging of Tumor Cells

Early detection of cancer can effectively improve the survival rate of cancer patients. Fluorescence imaging has the advantages of high sensitivity and rapid imaging, and is widely used in the precise imaging detection of tumors. In this study, five kinds of Au-rare earth bimetallic nanoclusters (Au/Ln NCs) were prepared by template method using five representative rare earth elements doped with gold. The morphologies, surface charges, sizes, fluorescence quantum yields and maximum fluorescence emission wavelengths of these five kinds of Au/Ln NCs were characterized and contrasted. The findings indicated that the Au/Ce nanoclusters (Au/Ce NCs) prepared by Ce doping have the longest fluorescence emission wavelength (695 nm) and higher quantum yield, which could effectively avoid the interference of autofluorescence, and was suitable for fluorescence imaging of tumor cells. In order to improve the specific accumulation of nanoclusters in tumor cells, Au/Ce NCs were coated with folic acid modified liposomes (lip-FA) to constructed a targeted fluorescent imaging probe with near-infrared response (Au/Ce@lip-FA), which was successfully used for fluorescence imaging of tumor cells. The probe has the characteristics of stable fluorescence signal, good targeting, easy internalization, and safe metabolism, and can provide high-resolution and high-brightness imaging information, which is expected to play an important role in the clinical diagnosis and surgical treatment of tumors.

Cyanine scaffold as dual-channel colorimetric and near-infrared emitting probe for sensitive detection of phosgene in environment and live cell

The detection of chemical warfare agent (CWA’s) in real time is obligatory in order to ease the threatening effect of these acute toxic agents to humankind. Herein, firstly we attempted, reversible, colorimetric, and fluorescent detection of phosgene in aqueous system succinctly described based on cyanine scaffold. Rapid and dual response of the probe was constructively employed to monitor the phosgene in the environment by strip test and soil analysis. The probe provides up to ppb (LOD of 0.08 ppb) level detection of phosgene with distinct color and fluorescence change. The turn-on near-infrared (NIR) fluorescence response bring in to play effectively to image trace level phosgene in live cell by fluorescent bio-imaging application.

Near-infrared toroidal dipole response supported by silicon metasurfaces.

The dielectric metasurfaces supporting non-radiative toroidal dipole resonances play important roles in nanophotonics. In this paper, toroidal dipole resonances using a double-axe nanostructure array in the near-infrared region are theoretically investigated by the characterization of the near-field distribution and far-field scattering. An experimental quality factor of 261 is obtained at the resonant wavelength of 1498 nm.

Dual-wavelength active and tunable modulation at telecommunication wavelengths using graphene-metal hybrid metamaterial based on plasmon induced transparency

Classic optical systems with a similar response to electromagnetically induced transparency (EIT) have received considerable attention. Plasmonically induced transparency (PIT) response is usually achieved by near-field coupling between resonators’ bright and dark modes. Most PIT structures are based on metamaterials and have a constant near-infrared spectral response; manipulating the PIT spectral response without changing the geometric structure and modifying the substrate or electrical biasing is impossible. A graphene-metal metamaterial structure is proposed to create an active tunable near-IR transparency window. In the proposed two-layer structure, the metal bars act as bright resonators in the upper layer. In the lower layer, the metal nanoribbons act as dark resonators and two sets of bilayer graphene are placed separately below the bright resonators and above the dark resonators. At first, the optimal induced transparency window is obtained by modifying the metal metamaterial’s geometrical parameters. Then, the properties of the generated induced window can be modified by varying the Fermi energies of the used graphene sheets in the hybrid metal-graphene metamaterial. The Fermi energies of the graphene sheets are adjusted by applying a voltage that causes the PIT phenomenon to be actively tunable. The proposed structure can be used as an active modulator in o and c communication bands. The designed modulator allows for 85% and 90% amplitude modulation depths (MD) at about 1307 nm and 1554 nm wavelengths.

Near-infrared response Pt-tipped Au nanorods/g-C3N4 realizes photolysis of water to produce hydrogen

• Ternary Pt-tipped Au nanorods/g-C 3 N 4 (Pt-Au/CN) heterostructure is constructed. • Pt-Au/CN shows H 2 evolution with a rate of 51.6 μ mol g −1 h −1 in the NIR region. • Pt-tipped Au nanorods shows two functions in photolysis of water to produce H 2 . The search for a suitable cocatalyst for graphitic carbon nitride (g-C 3 N 4 ) to realize efficient photocatalytic hydrogen (H 2 ) evolution has been regarded as one of the most valid tactics to alleviate energy crisis. Herein, a ternary Pt-tipped Au nanorods (Pt-Au)/g-C 3 N 4 heterostructure is constructed, which shows excellent H 2 production performance in visible and near-infrared (NIR) region, especially in NIR region with a rate of 51.6 μmol g −1 h −1 . Therein, not only is the optical absorption ability of g-C 3 N 4 broadened, the light absorption range is also extended to NIR region through introduction of Pt-Au architectures. Besides, analysis of the hot electrons generated in energy relaxation of plasmon indicates hot electron transfers fromexcited Au nanorods to Pt nanoparticles, resulting in H 2 evolution. Compared with bare g-C 3 N 4 , the superior photocatalytic activity could be attributed to the surface plasmon resonance effect (SPR) of Au nanorods and the electron-sink function of Pt nanoparticles. This work provides an insight into the improvement of photocatalytic performance via combination of NIR-responsive plasmon metal with photocatalysts.

NIR Photothermal-Responsive Shape Memory Polyurethane with Protein-Inspired Aggregated Chymotrypsin-Sensitive Degradable Domains.

Biodegradable shape memory polymers are promising biomaterials for stents used in minimally invasive surgical procedures such as intestinal stents. Herein, a series of biodegradable shape memory polyurethanes (SMPUs) containing a novel phenylalanine-derived chain extender (PHP) are synthesized. Inspired by the fact that the function of biomacromolecules such as proteins is rich and varied because of the multiple combinations of the amino acid in highly evolved biosystems, this study finds that the sequence distribution of PHP in SMPU will also have a great influence on the phase structure and degradation behavior, especially the difference of surface morphology caused by degradation. Considering that the transition temperature (Ttrans ) of SMPU obtained is higher than physiological temperature, oxidized carbon black (OCB) with the ability of photothermal conversion is introduced into SMPU, which can not only endow SMPU with near-infrared response shape recovery characteristics, but also enhance phase separation degree and mechanical properties of them. SMPU/OCB composites show excellent shape memory effect and rapid photothermal response, and they can be degraded by chymotrypsin with an adjustable degradation rate. These SMPU/OCB composites show broad potential for application as intestinal stents.

Photoemission from GaAs-based photocathodes with multilayer complex structures

To enhance the near-infrared response of photocathodes in the application of image detection, two kinds of multilayer complex structures of GaAs-based photocathodes are developed by changing the structure of the buffer layer underneath the emission layer, wherein one is the graded bandgap structure, and the other is the distributed Bragg reflector (DBR) structure. The theoretical quantum efficiency suitable for the reflection-mode (r-mode) GaAs-based photocathode with these two kinds of buffer structures are deduced based on one-dimensional continuity equations, among which the reflectivity changing with the wavelength of incident light is considered in particular. By comparison of spectral characteristics of photocathodes with the two different structures, and analysis of cathode structure parameters, it is found that the photoelectric performance of the photocathodes with the two structures are quite different, and the structure parameters especially the thickness of GaAs emission layer have a great impact on the spectral characteristic. The quantum efficiency of photocathode with graded bandgap structure is improved due to the introduction of the built-in electric field and the decrement of interface recombination, while for cathode with DBR structure, the quantum efficiency is improved by the multiple reflection of light between two parallel mirrors in the stack of alternating quarter-wave layers of high and low refractive. The theoretical quantum efficiency calculation and analysis would provide theoretical guidance for the better design of GaAs-based photocathodes.

High Performance Gold Nanorods@DNA Self-Assembled Drug-Loading System for Cancer Thermo-Chemotherapy in the Second Near-Infrared Optical Window.

In terms of synergistic cancer therapy, biological nanomaterials with a second near-infrared (NIR-II) window response can greatly increase photothermal effects and photoacoustic imaging performance. Herein, we report a novel stimuli-responsive multifunctional drug-loading system which was constructed by integrating miniature gold nanorods (GNR) as the NIR-II photothermal nanorods and cyclic ternary aptamer (CTA) composition as a carrier for chemotherapy drugs. In this system, doxorubicin hydrochloride (DOX, a chemotherapy drug) binds to the G-C base pairs of the CTA, which exhibited a controlled release behavior based on the instability of G-C base pairs in the slightly acidic tumor microenvironment. Upon the 1064 nm (NIR-II biowindow) laser irradiation, the strong photothermal and promoted cargo release properties endow gold nanorods@CTA (GNR@CTA) nanoparticles displaying excellent synergistic anti-cancer effect. Moreover, the GNR@CTA of NIR also possesses thermal imaging and photoacoustic (PA) imaging properties due to the strong NIR region absorbance. This work enables to obtaining a stimuli-responsive “all-in-one” nanocarrier, which are promising candidate for bimodal imaging diagnosis and chemo-photothermal synergistic therapy.

Enhancement of near-infrared response for GaAs-based photocathode with laminated graded-bandgap structure: theory and experiment

To enhance the quantum efficiency of GaAs-based photocathode in the near-infrared range, a laminated graded-bandgap photocathode structure consisting of a distributed Bragg reflection layer and a graded-bandgap emission layer is proposed. The theoretical optical properties and quantum efficiency of this proposed photocathode are simulated based on the finite-different time-domain method and the one-dimensional continuity equations, respectively. The absorptivity at 1064 nm can be significantly increased for the new-type photocathode because of the secondary absorption caused by the distributed Bragg reflection layer. With the improvement of absorptivity at 1064 nm, the quantum efficiency at specific wavelength is enhanced significantly. The contribution of the DBR structure and built-in electric field to the quantum efficiency is theoretical investigated respectively. According to theoretical structure design, the cathode samples grown by epitaxial technique are prepared to verify the theoretical prediction of quantum efficiency enhancement. After the treatment of surface cleaning and Cs/NF3 activation, the experimental results show that the minimum reflectivity at 1064 nm is realized, and the quantum efficiency of the sample with proposed structure is ten times than that of the sample without distributed Bragg reflection layer at 1064 nm. This research provides a guidance for the design of novel photocathode structures with enhanced response at special wavelength.

Study on biomimetic nano tumor targeted delivery system for chemotherapy-laser immunotherapy

To explore the immune adjuvant effect of nano mesoporous materials and laser immune effect of cancer therapy combined with chemotherapy, we designed a bionic nano tumor targeting delivery system with homologous cancer cell membrane as the outermost layer. Inorganic mesoporous silica (mSiO2) and hydroxyapatite (HAP) are used as the intermediate immune adjuvant layer and drug carrier layer, and gold nanorods(GNR) are used as the core. It degrade to release drug under the condition of low pH value, and the gold nanorods are wrapped for near-infrared laser response. Homologous cancer cell membrane wrapping is expected to greatly improve the efficiency of targeted delivery. Laser immunotherapy is more widely applied than antibody and vaccine, and has no serious side effects. Combined with controlled release drug targeted chemotherapy and encapsulated with tumor cell membrane, it is expected to further achieve low toxicity and high efficiency cancer treatment.

Dark Noise Suppression of NIR Response Enhanced Si-CMOS Sensor

We studied the effect of laser fluence on the dark noise performance of a laser-microstructured Si-based CMOS image sensor. The absorption characteristics and crystal properties of the microstructured sensor fabricated under different process conditions were investigated. Furthermore, a short-time etching method capable of improving the electrical performance of the laser-microstructured sensor was proposed. By removing amorphous silicon (a-Si) containing a large number of defects in the photosensitive surface of the microstructured Si-based CMOS image sensor, the etching method can effectively suppress the dark noise of the laser-microstructured Si-photodetector while maintaining the near-infrared response enhancement effect of the Si-photodetector irradiated by fs-laser. The results of the near-infrared imaging test show that on the basis of imaging brightness enhancement, the contrast ratio of the image formed by the CMOS image sensor in the microstructured region etched by RIE under short exposure time is significantly improved.

Structures and optical properties of thin tungsten oxide nanowires treated with poly(ethylene glycol)

Tungsten oxide (W18O49) nanowires exhibit a unique near-infrared optical response due to their oxygen defects, which is important for both basic research and device applications. The diameter of W18O49 nanowires strongly affects the performance of their thin films, and samples with smaller diameters are required for improvement of such device performances by taking an advantage of larger surface area. However, in the conventional synthesis process, aggregation of nanowires and bundle formation inhibit the preparation of nanowires with small diameters. In this study, we prepared W18O49 nanowire samples with relatively small diameters through the control of the aggregation using a dispersant such as poly(ethylene glycol) (PEG), and evaluated their structures and optical properties. We found that PEG treatment can effectively reduce the diameter of the bundles, and W18O49 nanowire samples mainly containing relatively small bundles with an average diameter of less than 10 nm were obtained.

Renal clearable polyfluorophore nanosensors for early diagnosis of cancer and allograft rejection.

Optical nanoparticles are promising diagnostic tools; however, their shallow optical imaging depth and slow clearance from the body have impeded their use for in vivo disease detection. To address these limitations, we develop activatable polyfluorophore nanosensors with biomarker-triggered nanoparticle-to-molecule pharmacokinetic conversion and near-infrared fluorogenic turn-on response. Activatable polyfluorophore nanosensors can accumulate at the disease site and react with disease-associated proteases to undergo in situ enzyme-catalysed depolymerization. This disease-specific interaction liberates renal-clearable fluorogenic fragments from activatable polyfluorophore nanosensors for non-invasive longitudinal urinalysis and outperforms the gold standard blood and urine assays, providing a level of sensitivity and specificity comparable to those of invasive biopsy and flow cytometry analysis. In rodent models, activatable polyfluorophore nanosensors enable ultrasensitive detection of tumours (1.6 mm diameter) and early diagnosis of acute liver allograft rejection. We anticipate that our modular nanosensor platform may be applied for early diagnosis of a range of diseases via a simple urine test.

Near-Infrared Light-Induced Photoresponse in Er3+/Li+-Codoped Y2O3/Poly(methyl methacrylate) Composite Film.

We demonstrate Li+-doping engineering for improving the near-infrared (NIR) photoresponse in an Er3+-activated Y2O3 phosphor. We show that the rational incorporation of Li+ results in a large enhancement of the upconversion (UC) emission intensity up to 29 times upon excitation of NIR light. The improved UC properties could be associated with the enhanced dipole-dipole transition probability due to Li+-induced changes in the local site symmetry for Er3+ ions and improvement in the crystallinity of the samples. We further demonstrate the construction of UC phosphor/polymer composite films by attaching the UC phosphor/polymer composite film onto a Si-photoresistor. The device shows a large enhancement of the photovoltage response from 0.16 to 0.4 V in Li-doped samples under NIR light illumination. These results suggest an effective doping strategy for the improvement of the UC performance of the oxide phosphor and its wide applications in solar energy utilization and NIR response devices.