High Upconversion Efficiency Research Articles

High-efficiency triplet-triplet annihilation upconversion microemulsion with facile preparation and decent air tolerance.

Current research of triplet-triplet annihilation upconversion (TTA-UC) faces difficulty such as overuse of organic solvents and quenching of excited triplet sensitizers by molecular oxygen. Herein, we propose an efficient and facile preparation strategy of TTA-UC microemulsion to overcome these issues. With simple device and short preparation process, air-stable TTA-UC with a high upconversion efficiency of 16.52% was achieved in microemulsion coassembled from TritonX114, tetrahydrofuran and upconverting chromophores (platinum octaethyl-porphyrin and 9,10-diphenylanthracene). This is comparable to the highest UC efficiency ever reported for TTA-UC microemulsion systems. The excellent UC performance of TX114-THF could be attributed to two perspectives. Firstly, small-size micelle accommodated chromophores up to high concentrations in organic phase, which promoted efficient molecular collision. Additionally, high absorbance at 532nm ensured full use of excitation light, getting more long wavelength photons involved in the TTA-UC process. Moreover, air-stable TTA-UC also performed well in microemulsion with various surfactants, including nonionic surfactants (Tween 20, Tween 80, Triton X-110, Triton X-114), ionic surfactants (sodium dodecyl sulfate, cetyltrimethyl ammonium bromide) and block copolymers (pluronic F127, pluronic P123), through three conjectural assembly models according to the structural characteristics of surfactant molecules (concentrated, uncompacted and scattered). These discoveries could provide estimable reference for selection of surfactants in relevant fields of TTA-UC.

Triplet-triplet annihilation photon upconversion-mediated photochemical reactions.

Photon upconversion is a method for harnessing high-energy excited states from low-energy photons. Such photons, particularly in the red and near-infrared wavelength ranges, can penetrate tissue deeply and undergo less competitive absorption in coloured reaction media, enhancing the efficiency of large-scale reactions and in vivo phototherapy. Among various upconversion methodologies, the organic-based triplet-triplet annihilation upconversion (TTA-UC) stands out - demonstrating high upconversion efficiencies, requiring low excitation power densities and featuring tunable absorption and emission wavelengths. These factors contribute to improved photochemical reactions for fields such as photoredox catalysis, photoactivation, 3D printing and immunotherapy. In this Review, we explore concepts and design principles of organic TTA-UC-mediated photochemical reactions, highlighting notable advancements in the field, as well as identify challenges and propose potential solutions. This Review sheds light on the potential of organic TTA-UC to advance beyond the traditional photochemical reactions and paves the way for research in various fields and clinical applications.

Fabrication, microstructure and upconversion luminescence properties of Er:Sr5(PO4)3F transparent nanostructured ceramics

Fluoride-upconversion transparent ceramic materials doped with Er ions have attracted extensive interest due to their higher stability, lower phonon energy, and higher upconversion efficiency. xEr:Sr5(PO4)3F (S-FAP) (x=0.5–5 at%) transparent ceramics have been synthesized by hot pressing sintering in this work, and the maximum optical transmittance of the sample reached 74.52 and 82.45% at 500 and 1000 nm, respectively. The XRD results of the powder and ceramic samples were consistent with the diffraction characteristics of the hexagonal S-FAP crystal structure. The SEM and TEM images of powder revealed that the morphology of the sample was composed of mostly rice grains with a diameter of around 20 nm. The XPS and EDS results confirmed the presence of Er3+ and the uniform distribution of Er elements. The thermally etched surface and cross section of ceramics revealed residual pores as the most important scattering source, and the SEM images of the ceramics show that Er doping can obviously promote the growth of the average grain size of S-FAP transparent ceramics. Furthermore, the upconversion luminescence characteristics and fluorescence lifespan of S-FAP transparent ceramics with varied Er doping concentrations were examined, as well as the upconversion luminescence process. The findings in this work indicate that Er:S-FAP transparent ceramics can be employed as a potential upconversion fluorescent material in display technology, biomedicine, temperature sensing, and other applications.

High-efficiency upconversion luminescence in UCNPs/CsPbBr3 nanocomposites enhanced by silver nanoparticles.

Upconversion nanocomposites with multiple light-emitting centers have attracted great attention as functional materials, but their low efficiency limits their further applications. Herein, a novel, to the best of our knowledge, system for nanocomposites consisting of upconversion nanoparticles (UCNPs) and perovskite quantum dots (PeQDs) assembled with Ag nanoparticles (NPs) is proposed. Upconversion luminescence (UCL) operation from PeQDs is triggered by near-infrared (NIR) sensitization through Förster resonance energy transfer (FRET) and photon reabsorption (PR). Especially, the photoluminescence (PL) emission efficiency is found to be significantly enhanced due to the increased energy transfer efficiency and radiative decay rate in the UCNPs/CsPbBr3 nanocomposites. The results offer new opportunities to improve the UCL properties of perovskites and open new development in the fields of LED lighting, solar cells, biomedicine, and so on.

Ambient solid-state triplet-triplet annihilation upconversion in ureasil organic-inorganic hybrid hosts.

Triplet-triplet-annihilation upconversion (TTA-UC) has attracted significant attention as an approach to harvest low energy solar photons that cannot be captured by conventional photovoltaic devices. However, device integration requires the design of solid-state TTA-UC materials that combine high upconversion efficiency with long term stability. Herein, we report an efficient solid-state TTA-UC system based on organic-inorganic hybrid polymers known as ureasils as hosts for the archetypal sensitiser/emitter pair of palladium(ii) octaethylporphyrin and diphenylanthracene. The role of the ureasil structure on the TTA-UC performance was probed by varying the branching and molecular weight of the organic precursor to tune the structural, mechanical, and thermal properties. Solid-state green-to-blue UC quantum yields of up to 1.86% were observed under ambient conditions. Notably, depending on the ureasil structure, UC emission could be retained for >70 days without any special treatment, including deoxygenation. Detailed analysis of the structure-function trends revealed that while a low glass transition temperature is required to promote TTA-UC molecular collisions, a higher inorganic content is the primary factor that determines the UC efficiency and stability, due to the inherent oxygen barrier provided by the silica nanodomains.

Effect of Yb3+ concentration on the upconversion emission properties of sub 10 nm RbY2F7:Yb, Er nanoparticles.

Upconversion nanoparticles (UCNPs) are a fascinating group of luminescent materials known for their ability to convert low-energy photons to high-energy photons. Many inorganic UCNPs have been studied to understand the underlying mechanism of upconversion phenomena, out of which alkali rare-earth fluorides (AREFs) such as NaREF4, LiREF4 and KREF4 were found to exhibit high upconversion efficiencies. This work investigates a similar AREF upconversion nanoparticle viz RbY2F7:Yb, Er. This UCNP system was synthesised by a modified thermal decomposition method by varying the Yb concentration from 20% to 98%. Structural analysis using XRD revealed that all the synthesised samples were found to be formed in the orthorhombic phase irrespective of the increasing Yb concentration. The thermal decomposition method greatly aided in the reduction of particle size. HRTEM analysis revealed that the as-synthesised UCNPs have a spherical morphology with an average particle size of 7.9 ± 0.2 nm. The upconversion emission studies taken by exciting the samples with a 975 nm laser show three distinct peaks at 527, 542 and 656 nm. The experimental results indicate that the increased Yb3+ concentration improves the red to green intensity ratio by supporting the 4F9/2 → 4I15/2 transition of Er3+ through the energy back transfer process between Er3+ and Yb3+. Notably, there is a reduction in the overall emission intensity with increasing Yb3+ concentration. Furthermore, the decay lifetime studies show a decreasing trend at 542 nm and 656 nm emission lines with an increase in the Yb concentration, which is because of the concentration quenching effect of the increasing Yb concentration.

Exploring the potential of lanthanide-doped oxyfluoride materials for bright green upconversion and their promising applications towards temperature sensing and drug delivery.

The most efficient upconversion (UC) materials reported to date are based on fluoride hosts with low phonon energies, which reduce the amount of nonradiative transitions. In particular, NaYF4 doped with Yb3+ and Er3+ at appropriate ratios is known as one of the most efficient UC phosphors. However, its low thermal stability limits its use for certain applications. On the other hand, oxide hosts exhibit better thermal stability, yet they have higher phonon energies and are thus prone to lower UC efficiencies. As a result, developing host nanomaterials that combine the robustness of oxides with the high upconversion efficiencies of fluorides remains an intriguing prospect. Herein, we demonstrate the formation of ytrrium doped oxyfluoride (YOF:Yb3+,Er3+) particles, which are prepared by growing a NaYF4:Yb3+,Er3+ layer around SiO2 spherical particles and consecutively applying a high-temperature annealing step followed by the removal of SiO2 template. Our interest lies in employing these materials as Boltzmann type physiological range luminescence thermometers, but their weak green emission is a drawback. To overcome this issue, and engineer materials suitable for Boltzmann type thermometry, we have studied the effect of introducing different metal ion co-dopants (Gd3+, Li+ or Mn2+) into the YOF:Yb3+,Er3+ particles, focusing on the overall emission intensity, as well as the green to red ratio, upon 975 nm laser excitation. These materials are explored for their use as ratiometric thermometers, and further also as drug carriers, including their simultaneous use for these two applications. The investigation also includes examining their level of toxicity towards specific human cells - normal human dermal fibroblasts (NHDFs) - to evaluate their potential use for biological applications.

A new ratiometric fluorescence nanosensor based on NaYF4:3%Er@NaYF4 upconversion nanoparticles for sensitive determination of Rose Bengal in water

Rose Bengal (RB) is used as a sensitizer in ambient water due to its property of catalyzing the production of singlet oxygen (1O2). However, this property also brings phototoxicity and carcinogenicity. The NaYF4:3%Er@NaYF4 core-shell upconversion nanoparticles (UCNPs) with higher upconversion efficiency was synthesized to detect RB in ambient water. Due to fluorescence resonance energy transfer (FRET) between RB and UCNPs, the upconversion fluorescence at 538 nm emitted by UCNPs was quenched by the RB, while the emission at 566 nm of RB raised. In the best conditions, the ratiometric emission intensity F566/F538 was positively proportional to RB concentration and the linear range was 0.04–15.0 μg·mL−1 (R2 = 0.996). The detection limit (S/N = 3) of RB was 2.46 ng·mL−1. The recoveries ranged from 99.0% to 105.6% (relative standard deviation 0.97–3.24%, n = 3) in tap water and 100.3%–104.9% (relative standard deviation 0.66–1.94%, n = 3) in lake water. This proposed method exhibits lower detection limit and larger linear, which possesses practical application value to the detection of RB in water.

Bodipy Dimer for Enhancing Triplet-Triplet Annihilation Upconversion Performance.

Triplet-triplet annihilation upconversion (TTA-UC) has considerable potential for emerging applications in bioimaging, optogenetics, photoredox catalysis, solar energy harvesting, etc. Fluoroboron dipyrrole (Bodipy) dyes are an essential type of annihilator in TTA-UC. However, conventional Bodipy dyes generally have large molar extinction coefficients and small Stokes shifts (<20 nm), subjecting them to severe internal filtration effects at high concentrations, and resulting in low upconversion quantum efficiency of TTA-UC systems using Bodipy dyes as annihilators. In this study, a Bodipy dimer (B-2) with large Stokes shifts was synthesized using the strategy of dimerization of an already reported Bodipy annihilator (B-1). Photophysical characterization and theoretical chemical analysis showed that both B-1 and B-2 can couple with the red light-activated photosensitizer PdTPBP to fulfill TTA-UC; however, the higher fluorescence quantum yield of B-2 resulted in a higher upconversion efficiency (ηUC) for PdTPBP/B-2 (10.7%) than for PdTPBP/B-1 (4.0%). This study proposes a new strategy to expand Bodipy Stokes shifts and improve TTA-UC performance, which can facilitate the application of TTA-UC in photonics and biophotonics.

High-efficiency upconversion process in cobalt and neodymium doped graphene QDs for biomedical applications

Multiphoton absorbing upconversion nanoparticles are emerging as bioimaging materials but are limited by the low quantum yield of their visible fluorescence. This article contains colloids of graphene quantum dots (GQDs), Neodymium, and Cobalt doped Graphene Quantum dots (Co-GQDs and Nd-GQDs) surrounded by carboxylic acids are synthesized which especially are suitable for bio applications; in this way, carboxylic acid groups exchanged by Amoxicillin as an antibiotic with bactericidal activity. The XRD diffraction method, TEM microscope, UV–Vis, and photoluminescence spectroscopies characterize the synthesized materials. The synthesized Quantum dots (QDs) exhibit upconversion properties and their emission is centered at 480 nm, but a red shift was observed with the increase of the excitation wavelength. In the emission spectra of synthesized QDs that can be related to the defect levels introduced by passivation of the QDs in the structure, the results show that with the interaction of the surface QDs with more carboxylic groups, the redshift is not observed. As the results indicate an increase in the intensity of upconversion emission is recorded for Co-GQDs and Nd-GQDs. The absolute quantum efficiency (QY) for Co-GQDs and Nd-GQDs were determined to be 41% and 100% more than GQDs respectively. DFT calculations indicate a strong bond between graphene and cobalt and Neodymium atoms. In doped materials, there are trap levels between the band gap of the GQDs which are responsible for increasing the intensity of the upconversion phenomenon.

Triplet–Triplet Annihilation Upconversion in a Porphyrinic Molecular Container

Triplet-triplet annihilation-based molecular photon upconversion (TTA-UC) is a photophysical phenomenon that can yield high-energy emitting photons from low-energy incident light. TTA-UC is believed to fuse two triplet excitons into a singlet exciton through several consecutive energy-conversion processes. When organic aromatic dyes─i.e., sensitizers and annihilators─are used in TTA-UC, intermolecular distances, as well as relative orientations between the two chromophores, are important in an attempt to attain high upconversion efficiencies. Herein, we demonstrate a host-guest strategy─e.g., a cage-like molecular container incorporating two porphyrinic sensitizers and encapsulating two perylene emitters inside its cavity─to harness photon upconversion. Central to this design is tailoring the cavity size (9.6-10.4 Å) of the molecular container so that it can host two annihilators with a suitable [π···π] distance (3.2-3.5 Å). The formation of a complex with a host:guest ratio of 1:2 between a porphyrinic molecular container and perylene was confirmed by NMR spectroscopy, mass spectrometry, and isothermal titration calorimetry (ITC) as well as by DFT calculations. We have obtained TTA-UC yielding blue emission at 470 nm when the complex is excited with low-energy photons. This proof-of-concept demonstrates that TTA-UC can take place in one supermolecule by bringing together the sensitizers and annihilators. Our investigations open up some new opportunities for addressing several issues associated with supramolecular photon upconversion, such as sample concentrations, molecular aggregation, and penetration depths, which have relevance to biological imaging applications.

Surface plasmon mediated harmonically resonant effects on third harmonic generation from Au and CuS nanoparticle films

Abstract A growing class of nonlinear materials employ the localized surface plasmonic resonance (LSPR) of nanoparticles to enhance harmonic generation. Material systems containing harmonically coupled metallic and semiconductor plasmonic nanoparticles have been shown to further increase performance. Here, we explore the effect of dual plasmonic interactions in bilayer CuS and Au nanoparticle films on third harmonic generation (THG). Detuning the CuS LSPR away from the excitation frequency changes the dominant upconversion pathway from THG to multiple photon photoluminescence (MPPL). Changing the size of the Au nanoparticle red shifts the LSPR from the second harmonic of the pump frequency and also eliminates the enhancement effect. When both LSPRs satisfy the harmonic condition, simultaneous excitation of CuS-Au nanoparticle films at the resonant frequency of each nanoparticle species enhances the generation of third harmonic light by sum-frequency generation, suggesting that the enhancement of THG in dually plasmonic nanoparticle films is the result of a cascaded nonlinear mechanism. An analytic model of the interaction between the plasmonic nanoparticles due to incoherent dipolar interactions is also presented. Understanding these processes opens a pathway for developing ultrafast, high-efficiency upconversion thin-film devices by clarifying the conditions that efficiently produce third harmonic generation without background MPPL or additional harmonics.

Upconversion enhancement through engineering the local crystal field in Yb3+ and Er3+ codoped BaWO4 along with excellent temperature sensing performance

Strong upconversion luminescence and excellent temperature sensing performance are simultaneously realized in BaWO4:Yb3+/Er3+ through Ca2+ doping.

A Compact Upconversion Single-Photon Imager for Full-Range and Accurate 3-D Imaging

The rapid development of single photon detection technology offers the possibility for an imaging system to go beyond the traditional limits. Recently, single-photon imagers based on upconversion technique have achieved unprecedentedly high resolution and noise tolerance in 3D imaging. Nevertheless, the limited imaging range, complicated optical path and long data acquisition time impose remaining challenges to practical applications. In this work, we build an upconversion single-photon imager for full-range and accurate 3D imaging. A compact all-fiber design allows our system to work robustly in an open environment. Compared to the previous imagers, the imaging speed is increased by three orders of magnitude due to the high upconversion efficiency and photon-efficient algorithm. With the application of a high-repetition laser and a nanosecond optical delay line, we achieve full-range imaging under the upconversion scheme against high solar background noise. For close-up scenes, our imager achieves ultrahigh axial resolution up to 20 μm, which is not affected by the time jitter or pileup effect of the single photon detector. Our proposal can stimulate practical applications in sophisticated scenarios.

Efficient low-power photon upconversion in core/shell heterostructured semiconductor nanowires

Photon energy upconversion, i.e. the conversion of several low-energy photons to a photon of higher energy, offers significant potential for nano-optoelectronics and nanophotonics applications. The primary challenge is to achieve high upconversion efficiency and a broad device performance range, enabling effective upconversion even at low excitation power. This study demonstrates that core/shell semiconductor nanowire heterostructures can exhibit upconversion efficiencies exceeding what was previously reported for semiconductor nanostructures even at a low excitation power of 100 mW/cm2, by a two-photon absorption process through conduction band states of the narrow-bandgap nanowire shell region. By engineering the electric-field distribution of the excitation light inside the NWs, upconversion efficiency can be further improved by eight times. This work showcases the effectiveness of the proposed approach in achieving efficient photon upconversion using core/shell NW heterostructures, resulting in some of the highest upconversion efficiencies reported in semiconductor nanostructures. Additionally, it offers design guidelines for enhancing energy upconversion efficiency.

High‐Efficiency Dual‐Mode Polychromatic Emission of Rare‐Earth‐Based Double Perovskite with Low Phonon Energy toward High‐Level Anti‐Counterfeiting and Information Encryption

AbstractThe development of rare‐earth‐doped luminescent materials with single component, multicolor, and multimode still remains a challenge. Here, rare‐earth‐based double perovskite single crystals (Cs2NaYbCl6 DPSCs) are fabricated with low phonon energy of 134 cm−1, which offers great potential to serve as highly efficient luminescent host materials. Subsequently, Er3+, Tm3+, and Ho3+ are successfully incorporated into Cs2NaYbCl6 host to form Cs2NaLnxYb1−xCl6 (Ln = Er, Tm, and Ho) DPSCs, realizing efficient dual‐mode polychromatic emission. Under 980 nm laser excitation, Cs2NaLnxYb1−xCl6 DPSCs show high upconversion (UC) efficiencies of 12.9%, 7.2%, and 3.1% for Cs2NaEr0.3Yb0.7Cl6, Cs2NaTm0.02Yb0.98Cl6, and Cs2NaHo0.3Yb0.7Cl6, respectively. Meanwhile, Cs2NaErxYb1−xCl6 DPSCs exhibit the adjustable size (0.5–10 mm) and tunable UC or down‐shifting emission colors from yellow, green to red upon 980, 1540, or 380 nm excitation. Moreover, the DPSCs demonstrate weak concentration and thermal quenching effect, and excellent resistance against oxygen, heat and humidity. Finally, the anti‐counterfeiting and information encryption applications based on multicolor emitting DPSCs are designed and realized.

Boosting photocatalytic hydrogen evolution via triplet–triplet annihilation upconversion

To enhance the light-harvesting ability of photocatalytic splitting water system, triplet–triplet annihilation upconversion (TTA-UC) is integrated with photocatalysis directly for the first time via a detergent-free ternary toluene/isopropanol/water microemulsion system. TTA-UC pairs containing PtOEP/PdTPTBP/PdTPNEt2P and perylene are combined with Cd0.5Zn0.5S for photocatalytic hydrogen production. These TTA-UC pairs convert visible light with the wavelength >510 nm that cannot be absorbed directly by Cd0.5Zn0.5S into blue light with smaller wavelength. Cd0.5Zn0.5S is then sensitized by this upconverted blue light to produce hydrogen. More importantly, the hydrogen production rate (8.44 mmol g-1h−1) of this integrated photocatalytic system is twice as high as that of the pure Cd0.5Zn0.5S microemulsion (4.04 mmol g-1h−1) under visible light (λ > 420 nm) irradiation, which is the best performance for the TTA-UC integrated photocatalytic system for hydrogen evolution ever reported so far. The high upconversion efficiency and high utilization efficiency of upconversion emission in microemulsion are responsible for the significantly promoted catalytic performance of this integrated photocatalytic system. The result demonstrates a simple strategy to integrate TTA-UC with photocatalyst for enhancing the hydrogen production efficiency. Considering the easily-tunable excitation/emission wavelength of TTA-UC pairs, this method could be used to integrate TTA-UC with a variety of photocatalysts.

Interfacial charge transfer states enable efficient solid-state upconversion

While high-efficiency upconversion is widely demonstrated in solution, solid-state upconversion has lagged significantly behind. Recently, Hiramoto et al. reported a novel solid-state upconversion system based on organic semiconductor heterojunctions, leading to more than 10-fold improvement in efficiency.

Designing Semiconductor Nanowires for Efficient Photon Upconversion via Heterostructure Engineering.

Energy upconversion via optical processes in semiconductor nanowires (NWs) is attractive for a variety of applications in nano-optoelectronics and nanophotonics. One of the main challenges is to achieve a high upconversion efficiency and, thus, a wide dynamic range of device performance, allowing efficient upconversion even under low excitation power. Here, we demonstrate that the efficiency of energy upconversion via two-photon absorption (TPA) can be drastically enhanced in core/shell NW heterostructures designed to provide a real intermediate TPA step via the band states of the narrow-bandgap region with a long carrier lifetime, fulfilling all the necessary requirements for high-efficiency two-step TPA. We show that, in radial GaAs(P)/GaNAs(P) core/shell NW heterostructures, the upconversion efficiency increases by 500 times as compared with that of the constituent materials, even under an excitation power as low as 100 mW/cm2 that is comparable to the 1 sun illumination. The upconversion efficiency can be further improved by 8 times through engineering the electric-field distribution of the excitation light inside the NWs so that light absorption is maximized within the desired region of the heterostructure. This work demonstrates the effectiveness of our approach in providing efficient photon upconversion by exploring core/shell NW heterostructures, yielding an upconversion efficiency being among the highest reported in semiconductor nanostructures. Furthermore, our work provides design guidelines for enhancing efficiency of energy upconversion in NW heterostructures.

Fully Integrated Ultra-thin Intraoperative Micro-imager for Cancer Detection Using Upconverting Nanoparticles

PurposeIntraoperative detection and removal of microscopic residual disease (MRD) remain critical to the outcome of cancer surgeries. Today’s minimally invasive surgical procedures require miniaturization and surgical integration of highly sensitive imagers to seamlessly integrate into the modern clinical workflow. However, current intraoperative imagers remain cumbersome and still heavily dependent on large lenses and rigid filters, precluding further miniaturization and integration into surgical tools.ProceduresWe have successfully engineered a chip-scale intraoperative micro-imager array—without optical filters or lenses—integrated with lanthanide-based alloyed upconverting nanoparticles (aUCNPs) to achieve tissue imaging using a single micro-chip. This imaging platform is able to leverage the unique optical properties of aUCNPs (long luminescent lifetime, high-efficiency upconversion, no photobleaching) by utilizing a time-resolved imaging method to acquire images using a 36-by-80-pixel, 2.3 mm times 4.8 mm silicon-based electronic imager micro-chip, that is, less than 100-µm thin. Each pixel incorporates a novel architecture enabling automated background measurement and cancellation. We have validated the performance, spatial resolution, and the background cancellation scheme of the imaging platform, using resolution test targets and mouse prostate tumor sample intratumorally injected with aUCNPs. To demonstrate the ability to image MRD, or tumor margins, we evaluated the imaging platform in visualizing a single-cell thin section of the injected prostate tumor sample.ResultsTested on USAF resolution targets, the imager is able to achieve a resolution of 71 µm. We have also demonstrated successful background cancellation, achieving a signal-to-background ratio of 8 when performing ex vivo imaging on aUCNP-injected prostate tumor sample, improved from originally 0.4. The performance of the imaging platform on single-cell layer sections was also evaluated and the sensor achieved a signal-to-background ratio of 4.3 in resolving cell clusters with sizes as low as 200 cells.ConclusionThe imaging system proposed here is a scalable chip-scale ultra-thin alternative for bulky conventional intraoperative imagers. Its novel pixel architecture and background correction scheme enable visualization of microscopic-scale residual disease while remaining completely free of lenses and filters, achieving an ultra-miniaturized form factor—critical for intraoperative settings.