Immune-modulative nano-gel-nano system for patient-favorable cancer therapy.

Current cancer immunotherapies exhibit low response rates attributed to suppressive tumor immune microenvironments (TIMEs). To address these unfavorable TIMEs, supplementation with tumor-associated antigens and stimulation of immune cells at target sites are indispensable for eliciting anti-tumoral immune responses. Previous research has explored the induction of immunotherapy through multiple injections and implants; however, these approaches lack consideration for patient convenience and the implementation of finely tunable immune response control systems to mitigate the side effects of over-inflammatory responses, such as cytokine storms. In this context, we describe a patient-centric nano-gel-nano system capable of sustained generation of tumor-associated antigens and release of adjuvants. This is achieved through the specific delivery of drugs to cancer cells and antigens/adjuvants to immune cells over the long term, maintaining proper concentrations within the tumor site with a single injection. This system demonstrates local immunity against tumors with a single injection, enhances the therapeutic efficacy of immune checkpoint blockades, and induces systemic and memory T cell responses, thus minimizing systemic side effects.

Telomere Length Measurement in Human Tissue Sections by Quantitative Fluorescence In Situ Hybridization (Q-FISH).

Telomeres in most somatic cells shorten with each cell division, and critically short telomeres lead to cellular dysfunction, cell cycle arrest, and senescence. Thus, telomere shortening is an important hallmark of human cellular senescence. Quantitative fluorescence in situ hybridization (Q-FISH) using formalin-fixed paraffin-embedded (FFPE) tissue sections allows the estimation of telomere lengths in individual cells in histological sections. In our Q-FISH method, fluorescently labelled peptide nucleic acid (PNA) probes are hybridized to telomeric and centromeric sequences in FFPE human tissue sections, and relative telomere lengths (telomere signal intensities relative to centromere signal intensities) are measured. This chapter describes our Q-FISH protocols for assessing relative telomere lengths in FFPE human tissue sections.

Toward understanding ammonia capture in two amino-functionalized metal-organic frameworks using in-situ infrared spectroscopy and DFT calculation.

Two isostructural, three-dimensional, interpenetrated amino-functionalized Metal-Organic Frameworks (Co-2AIN-MOF and Cd-2AIN-MOF) based on 2-aminoisonicotinic acid (2AIN) were synthesized, structurally characterized and determined. Based on the PXRD analysis, the solvent exchange hardly changed their framework structure, and the samples fully activated by methanol can be achieved and examined by infrared spectroscopy. Due to the presence of the carbonyl group and free amino groups in the pore of the framework, the NH3 uptakes of Co-2AIN-MOF and Cd-2AIN-MOF are 11.70 and 13.81 mmol/g and at 1 bar, respectively. In-situ Infrared spectroscopy and DFT calculations revealed the different adsorption sites and processes between Co-2AIN-MOF and Cd-2AIN-MOF.

Recycling Fe and improving organic pollutant removal via in situ forming magnetic core-shell Fe3O4@CaFe-LDH in Fe(II)-catalyzed oxidative wastewater treatment.

Due to its high efficiency, Fe(II)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants. A lot of chemical Fe sludge along with various refractory pollutants was concomitantly produced, which may cause secondary environmental problems without proper disposal. We here innovatively proposed an effective method of achieving zero Fe sludge, reusing Fe resources (Fe recovery = 100%) and advancing organics removal (final TOC removal > 70%) simultaneously, based on the in situ formation of magnetic Ca-Fe layered double hydroxide (Fe3O4@CaFe-LDH) nano-material. Cations (Ca2+ and Fe3+) concentration (≥ 30 mmol/L) and their molar ratio (Ca:Fe ≥ 1.75) were crucial to the success of the method. Extrinsic nano Fe3O4 was designed to be involved in the Fe(II)-catalytic wastewater treatment process, and was modified by oxidation intermediates/products (especially those with COO- structure), which promoted the co-precipitation of Ca2+ (originated from Ca(OH)2 added after oxidation process) and by-produced Fe3+ cations on its surface to in situ generate core-shell Fe3O4@CaFe-LDH. The oxidation products were further removed during Fe3O4@CaFe-LDH material formation via intercalation and adsorption. This method was applicable to many kinds of organic wastewater, such as bisphenol A, methyl orange, humics, and biogas slurry. The prepared magnetic and hierarchical CaFe-LDH nanocomposite material showed comparable application performance to the recently reported CaFe-LDHs. This work provides a new strategy for efficiently enhancing the efficiency and economy of Fe(II)-catalyzed oxidative wastewater treatment by producing high value-added LDHs materials.

Synthesis of δ-MnO2 via ozonation routine for low temperature formaldehyde removal.

Nowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, δ-MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2+ is oxidized by ozone (O3) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85°C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2. Characterizations show that ozonation process generates a different intermediate of tetragonal ß-HMnO2, which would favor the quick transformation into the final product δ-MnO2, as compared with the relatively more thermodynamically stable monoclinic γ-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature in-situ diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active δ-MnO2 synthesis in order to remove the HCHO contamination.

The Changing Phases of Bromopentafluorobenzene.

As part of a much larger study on non-covalent interactions in binary adducts, we have explored the solid-state structures of bromopentafluorobenzene (C6F5Br) using differential scanning calorimetry (DSC), variable-temperature powder X-ray diffraction (VT-PXRD), and single-crystal X-ray diffraction (SXD). DSC data initially indicated a single solid-state phase below the freezing point, but revealed additional weak transitions upon heating. The crystal structures of three solid-state phases have been solved. The SXD data showed that phases I and IV are centrosymmetric, whilst phase II is polar. However, the structure of phase III remains elusive due to the changing phase behaviour of C6F5Br that is determined as much as by kinetics as thermodynamics. The results underline the need for multiple analytical techniques to study non-covalent interactions and offer valuable data for refining computational models in crystal structure prediction and machine learning. A comparison with the iodinated counterpart is also made.

Electronic Metal-Support Interaction Induces Hydrogen Spillover and Platinum Utilization in Hydrogen Evolution Reaction.

The substantial promotion of hydrogen evolution reaction (HER) catalytic performance relies on the breakup of the Sabatier principle, which can be achieved by the alternation of the support and electronic metal support interaction (EMSI) is noticed. Due to the utilization of tungsten disulfides as support for platinum (Pt@WS2), surprisingly, Pt@WS2 demands only 31 mV overpotential to attain 10 mA cm-2 in acidic HER test, corresponding to a 2.5-fold higher mass activity than benchmarked Pt/C. The pH dependent electrochemical measurements associated with H2-TPD and in-situ Raman spectroscopy indicate a hydrogen spillover involved HER mechanism is confirmed. The WS2 support triggers a higher hydrogen binding strength for Pt leading to the increment in hydrogen concentration at Pt sites proved by upshifted d band center as well as lower Gibbs free energy of hydrogen, favourable for hydrogen spillover. Besides, the WS2 shows a comparably lower effect on Gibbs free energy for different Pt layers (-0.50 eV layer-1) than carbon black (-0.88 eV layer-1) contributing to a better Pt utilization. Also, the theoretical calculation suggests the hydrogen spillover occurs on the 3rd Pt layer in Pt@WS2; moreover, the energy barrier is lowered with increment in hydrogen coverage on Pt.

Quality of life issues in patients with ductal carcinoma in situ: a systematic review.

PURPOSE: Ductal carcinoma in situ (DCIS) of the breast is one of the most common pre-invasive cancers diagnosed in women. Quality of life (QoL) is extremely important to assess in studies including these patients due to the favorable prognosis of the disease. The primary objective of this systematic review was to compile a comprehensive list of QoL issues, all existing QoL assessment tools, and patient-reported outcome measures used to assess DCIS. METHODS: A search was conducted on Ovid MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases from inception to August 2023, using keywords such as "ductal carcinoma in-situ", "quality of life", and "patient-reported outcomes." QoL issues and QoL tools in primary research studies were extracted. RESULTS: A total of 67 articles identified issues pertaining to patients with DCIS spanning physical, functional, and psychosocial QoL domains. Physical and functional issues observed in patients included pain, fatigue, and impaired sexual functioning. Psychosocial issues such as anxiety, depression, and confusion about one's disease were also common. QoL tools included those that assessed general QoL, breast cancer-specific tools, and issue-specific questionnaires. CONCLUSION: The current instruments available to assess QoL in patients with DCIS do not comprehensively capture the issues that are pertinent to patients. Thus, the modification of existing tools or the creation of a DCIS-specific QoL tool is recommended to ensure that future research will be sensitive towards challenges faced by patients with DCIS.

Observation on Switching Properties of WO3-Based H2 Sensor Regulated by Temperature and Gas Concentration.

Transition metal oxide semiconductors have great potential for use in H2 sensors, but in recent years, the strange phenomena about gas-sensitive performance associated with their special properties have been more widely discussed in research. In some cases, the resistance of transition metal oxide gas sensors will emerge with some changes contrary to their intrinsic semiconductor characteristics, especially in gas sensor research of WO3. Based on the hydrothermal synthesis of WO3, our work focuses on the abnormal change of tungsten oxide resistance to different gases at low temperature (80-200 °C) and high temperature (above 200 °C). Through in situ FT-IR and in situ XPS, combined with density functional theory calculations, a new reasonable explanation of WO3 is proposed for the abnormal resistance change caused by temperature and the strange response due to gas concentration. The occurrence of these findings can be attributed to the synergistic effect resulting from the presence of two contributing factors. One of them is attributed to the alteration in the surface valence state of WO3 induced by gas, resulting in the reduction of W6+. The other one is due to the reaction between gas and adsorbed oxygen on the surface of WO3. This work presents a novel and rational concept for addressing the reaction mechanism between gas and transition metal oxide semiconductors, thereby paving the way for the development of highly efficient gas sensors based on transition metal oxide semiconductors.

Judicious use of precise fluorescence in situ hybridisation panels guided by population prevalence may assist pragmatic detection of clinically targetable Philadelphia chromosome-like acute lymphoblastic leukaemia fusions: a systematic review.

Diagnosis of Philadelphia chromosome-like acute lymphoblastic leukaemia (Ph-like ALL) in the real-world remains challenging because of definitional complexities, the diverse diagnostic techniques available and the cost, expertise and time involved. We summarise evidence for diagnosis of clinically important Ph-like ALL related genomic lesions using fluorescence in situ hybridisation (FISH) targeting only clinically important and actionable lesions, an accessible and cost-effective diagnostic technique. Electronic databases were interrogated using broad MeSH terms for articles reporting a detailed FISH strategy for diagnosis of Ph-like ALL published since 2014, yielding 653 full text articles and abstracts. We searched the National Library of Medicine Databases including PubMed, Medline, Embase, Cochrane and relevant abstracts. We included studies with a primary aim of determining the utility of FISH for Ph-like ALL diagnosis and studies with broader aims demonstrating Ph-like ALL diagnostic algorithms which partially involved FISH. Nineteen studies met inclusion criteria. Evidence for FISH to detect CRLF2 rearrangements in Ph-like ALL is strongly established and evidence for FISH to detect non-CRLF2 lesions is evolving rapidly. We documented 1620 cases of non-CRLF2 Ph-like lesions diagnosed by FISH. Confirmatory side-by-side methods were applied in six studies (246 samples), four of which demonstrated 100% concordance of FISH results with alternative methods, while two studies demonstrated over 70% sensitivity and specificity. Additional studies demonstrated wide utilisation of FISH in Ph-like ALL classification across diverse geographies and ethnicities, with contrasting prevalence, implicating a need for targeted FISH strategies. In real-world cohorts, it may be clinically useful to prioritise limited early FISH in B-cell ALL (B-ALL) diagnostic algorithms to identify Ph-like abnormalities that respond to locally available kinase inhibitors to promote and prioritise broad access to effective targeted treatment. Additional studies are required to provide adequately powered validations and verifications of targeted Ph-like FISH panels to confirm sensitivity and specificity against side-by-side gold standard methods, and to define optimal local approaches.

Mechanistic Understanding of the Underlying Energy Storage Mechanism of α-MnO2-based Pseudo-Supercapacitors.

Manganese dioxide (α-MnO2) has attracted significant research interest in supercapacitors recently. However, the reaction mechanism of α-MnO2 in supercapacitors remains unclear. Therefore, a nano-supercapacitor using Environmental transmission electron microscopy (ETEM) is conducted and investigated the reaction mechanism of α-MnO2 based on three ionic liquids (ILs). It found that in the aprotic ionic liquid (AIL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIMOTF), α-MnO2 nanowires (NWs) undergo an oxidation reaction due to the presence of an active proton at the second position (H2) of the imidazole ring. As a result, α-MnO2 NWs undergo a phase transition and transform into Mn3O4, exhibiting pseudo-capacitive properties. Furthermore, characterization of the macroscopic α-MnO2 electrodes after cycling reveals that after the initial charging cycles, the dominant energy storage mechanism of the supercapacitor transitions from pseudo-capacitance to a dual-layer capacitance formed by the combination of Mn3O4 and unreacted α-MnO2. Simultaneously, due to the coexistence of these two energy storage mechanisms, the specific capacitance of the supercapacitor in EMIMOTF electrolyte reaches up to 80 F g-1, and the cycle number reaches as high as 1000 cycles. The results are expected to provide insights into the selection of electrolytes in supercapacitors and offer a fundamental understanding of the internal reaction mechanisms in capacitors.

Improving monitoring of dissolved organic matter from the wastewater treatment plant to the receiving environment: A new high-frequency in situ fluorescence sensor capable of analyzing 29 pairs of Ex/Em wavelengths.

A high-frequency, in situ fluorescence probe, called Fluocopée®, has been developed in order to better monitor variations in both the quality and quantity of dissolved organic matter within various aquatic environments (e.g. wastewater, receiving environments) thanks to a wide choice of 29 measured Excitation/Emission wavelength pairs. This advance pave the way to new measurement possibilities in comparison with existing probes, which are usually only able to measure 1-4 fluorophores. The qualification tests of the Fluocopée® probe indicate a high level of accuracy for the measurements of tyrosine, tryptophan and humic acids solutions. Good repeatability and reproducibility are also observed. For the first time, this tool has been deployed in an urban watershed (Bougival, Seine River, downstream of Paris) and in the settled effluent from a wastewater treatment plant (Seine aval, Achères, France). This new high-frequency in situ probe offers great application potential, including organic matter quality and quantity monitoring at drinking and wastewater treatment plants (treatment optimization) and in continental and marine waters (the fate of organic matter in biogeochemical cycles).

Tracing pesticide dynamics: High resolution offers new insights to karst groundwater quality.

Generally, karst aquifers and springs are highly susceptible to contamination due to the high permeability and, therefore, groundwater flow velocities. The often thin soil cover, accompanied by dolines, can lead to fast infiltration of precipitation water loaded with mobilized contaminants such as pesticides and their transformation products. To date, continuous, temporally highly resolved in-situ monitoring to decipher concentration dynamics for a broad range of pesticides is missing. Therefore, a transportable HPLC-HRMS/MS system (MS2field) was positioned at two karst study sites in the Swiss Jura. Water samples were collected and analyzed for pesticides and their transformation products in-situ every 20 min for 6 weeks in 2021 and 8 weeks in 2022. During the spraying season in 2021, six rain events at site 1 and three at site 2 in 2022 were captured. Concurrently, the water quality parameters electrical conductivity, pH, nitrate, turbidity, and water level, were monitored continuously at high temporal resolution. Further, bacterial cell counts were monitored via online flow cytometry. In 2021, several pesticides and pesticide transformation products were detected in peak concentrations after rain events, of which metamitron showed the highest concentration of up to 1000 ng/L. In one rain event, the Swiss federal and EU drinking water limit of 100 ng/L was exceeded for up to 38 h. Compared with highly frequent MS2field samples collected every 20 min, 42-hours composite samples severely underestimated peak concentrations for all compounds, especially for labile ones. Therefore, it was demonstrated that exceedences of the regulatory limit would have been missed if just composite sampling would have been conducted. Peak concentrations of pesticides coincided with peaks in nitrate concentration and bacterial cell counts following rain events. The correlation analysis showed strong correlations between the three analyzed contaminants (pesticides, nitrate and bacteria), and the proxy parameters electrical conductivity, and pH. The investigation of a second spring revealed similar dynamics indicating that these can be expected in other karst aquifers as well.

Electrochemical production of HO2- and O2 for sulfide removal from sewage.

In this study, a comparative analysis of two electrochemical methods for sulfide control in sewer networks was performed for the first time. In addition, the mechanism of sulfide control by HO2- was elucidated, and an analysis of the device operation and electrolyte selection was performed. The two-electron oxygen reduction reaction (2e--ORR) using untreated gas diffusion electrode (GDE) was superior to the hydrogen evolution reaction (HER) using stainless-steel mesh in terms of cell voltage, product formation, and sulfide suppression. The GDE maintained a stable HO2⁻ production capacity, achieving a concentration of 4566.6 ± 173.3 mg L⁻¹ with a current efficiency (CE) of 84.13 ± 3.5 %. During the electrolysis period, a stable dissolved oxygen (DO) level in sewage was consistently observed due to continuous in-situ oxygen production in anode. HO2- exhibited a notable increase in sewage pH (10.20 ± 0.01), effectively inhibiting the release of 99.93 % of sulfides. Moreover, the combined treatment of HO2- and DO significantly surpassed that of individual treatments. Seawater treated with cation exchange resin (CER) emerged as the most promising alternative to freshwater as the electrolyte. Overall, this study demonstrates that in-situ generation of HO2⁻ and oxygen is a more effective strategy for sulfide control in sewer systems.

In Situ Fabrication of Highly Efficient and Stable Cs2NaInCl6: Sb3+@PVDF Composite Films for Optoelectronic Devices.

Lead-free double perovskites (DPs) have superior phase stability and optical properties, which make them competitive for future applications in illumination and displays. However, the preparation of DPs was mainly based on high-temperature heating and hydrochloric acid as a solvent to form powders, which increased the risk and cost of the preparation process and limited its further application. In this study, the growth of Cs2NaInCl6: Sb3+ DPs in polyvinylidene difluoride (PVDF) films was achieved using an in situ fabrication strategy with DMSO as the solvent. The prepared Cs2NaInCl6: Sb3+@PVDF composite films (CFs) can achieve a bright blue emission under 302 nm irradiation. To achieve the optimal luminescent performance of CFs, the photoluminescence (PL) intensity of Cs2NaInCl6: Sb3+@PVDF CFs under various in situ preparation conditions was compared. In addition, the photoluminescence quantum yield (PLQY) of CFs was increased from 0.72% to 83.77% by adjusting the doping amount of Sb3+, and the fluorescence lifetimes t1 and t2 were 131.08 and 1048.52 ns, respectively. Temperature-dependent PL spectroscopy and density functional theory (DFT) calculations indicate that these excellent optical properties are derived from the self-trapped excitons (STEs) at the [SbCl6]3- octahedron and [InCl6]3- octahedron connected via Cl-Na-Cl. The CFs also demonstrated excellent environmental stability, maintaining a relatively stable PL intensity even under conditions of water immersion, high temperatures, and ultraviolet (UV) radiation. Finally, we used the CFs to assemble a blue light-emitting device (LED), which showed good and stable blue emission performance at different currents. This work can provide a new idea for preparing DPs, which is conducive to promoting their commercial application in high-performance optoelectronic devices.

Microheater Controlled Crystal Phase Engineering of Nanowires Using In Situ Transmission Electron Microscopy.

Crystal Phase Quantum Dots (CPQDs) offer promising properties for quantum communication. How CPQDs can be formed in Au-catalyzed GaAs nanowires using different precursor flows and temperatures by in situ environmental transmission electron microscopy (ETEM) experiments is studied. A III-V gas supply system controls the precursor flow and custom-built micro electro-mechanical system (MEMS) chips with monocrystalline Si-cantilevers are used for temperature control, forming a micrometer-scale metal-organic vapor phase epitaxy (µMOVPE) system. The preferentially formed crystal phases are mapped at different precursor flows and temperatures to determine optimal growth parameters for either crystal phase. To control the position and length of CPQDs, the time scale for crystal phase change is investigated. The micrometer size of the cantilevers allows temperature shifts of more than 100 °C within 0.1 s at the nanowire growth temperature, which can be much faster than the growth time for a single lattice layer. For controlling the crystal phase, the temperature change is found to be superior to precursor flow, which takes tens of seconds for the crystal phase formation to react. This µMOVPE approach may ultimately provide faster temperature control than bulk MOVPE systems and hence enable engineering sequences of CPQDs with quantum dot lengths and positions defined with atomic precision.

Unraveling the Potential Dependence of Active Structures and Reaction Mechanism of Ni-based MOFs Electrocatalysts for Alkaline OER.

Nickel-based metal-organic frameworks (MOFs) with flexible structure units provide a broad platform for designing highly efficient electrocatalysts, especially for alkaline oxygen evolution reaction (OER). However, the stability of MOFs under harsh and dynamic reaction conditions poses significant challenges, resulting in ambiguous structure-activity relationships in MOFs-based OER research. Herein, Ni-benzenedicarboxylic acid-based MOF (NiBDC) is selected as prototypical catalyst to elucidate  its real active sites for OER and reaction pathway under different reaction states. Electrochemical measurements combined with X-ray absorption spectroscopy (XAS) and Raman spectroscopy reveal that the complete reconstruction of NiBDC to ß-NiOOH in the chronoamperometry activation process is responsible for significantly increased OER performance. In situ XAS and Raman results further demonstrate the electro-oxidation of ß-NiOOH into γ-NiOOH at high-potential state (above 1.6 V vs RHE). Furthermore, the collective evidences from key reaction intermediates and isotope-labeled products definitely unravel the potential dependence of OER mechanism: OER process at low-potential state proceeds mainly through the lattice oxygen-mediated mechanism, while adsorbate evolution mechanism emerges as the predominant pathway at high-potential state. Interestingly, the dynamically changing OER mechanism can not only reduce the required overpotential at the low-potential state but also improve the electrochemical stability of catalysts at high-potential state.

In Situ Characterization of Interface Evolution in Argyrodite-Based All-Solid-State Li Batteries.

Interfacial stability is one of the critical challenges in all-solid-state Li metal batteries. Multiple processes such as solid electrolyte (SE) decomposition and lithium dendrite growth take place at the solid interfaces during cycling, leading to the overall cell failure. To deconvolute these complex processes, in situ characterization is of paramount importance to elucidate the interfacial evolution on the SE upon Li plating/stripping. Herein, an all-solid-state asymmetric in situ cell is developed that allows the direct visualization of the highly localized Li plating/stripping processes under the optical microscope. Moreover, this cell configuration enables reliable post-mortem chemical and morphological analysis of the intact SE/Li interface. Using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy, the study reveals that the evolution of the Li argyrodite interface is strongly influenced by the current density, particularly in terms of chemical distribution and Li plating morphology. More specifically, the solid interface is LiCl-rich with the formation of Li cubes at low current densities, while high currents result in more uniform elemental distribution and filament morphology. These findings elucidate the dynamic evolution mechanism at solid interfaces and offer valuable guidance for developing stable solid interfaces in all-solid-state Li metal batteries.

Precision in situ cryo-correlative light and electron microscopy of optogenetically-positioned organelles.

Unambiguous targeting of cellular structures for in situ cryo-electron microscopy in the heterogeneous, dense, and compacted environment of the cytoplasm remains challenging. Here we have developed a cryogenic correlative light and electron microscopy (cryo-CLEM) workflow which combines thin cells grown on a mechanically defined substratum to rapidly analyse organelles and macromolecular complexes by cryo-electron tomography (cryo-ET). We coupled these advancements with optogenetics to redistribute perinuclear-localised organelles to the cell periphery, allowing visualisation of organelles otherwise positioned in cellular regions too thick for cryo-ET. This reliable and robust workflow allows for fast in situ analyses without the requirement for cryo-focused ion beam milling. Using this protocol, cells can be frozen, imaged by cryo-fluorescence microscopy and be ready for batch cryo-ET within a day.

End-To-End FRET Enabling Direct Measurement of Oligomer Chain Conformations and Molecular Weight in Reaction Solutions.

Förster resonance energy transfer (FRET) is an established tool for measuring distances between two molecules (donor and acceptor) on the nanometer scale. In the field of polymer science, the use of FRET to measure polymer end-to-end distances (Ree) often requires complex synthetic steps to label the chain ends with the FRET pair. This work reports an anthracene-functionalized chain-transfer agent for reversible addition-fragmentation chain-transfer (RAFT) polymerization, enabling the synthesized chains to be directly end-labeled with a donor and acceptor without the need for any post-polymerization functionalization. Noteworthily, this FRET method allows for chain conformation measurements of low molecular weight oligomers in situ, without any work-up steps. Using FRET to directly measure the average Ree of the oligomer chains during polymerization, the chain growth of methyl methacrylate, styrene, and methyl acrylate is investigated as a function of reaction time, including determining their degree of polymerization (DP). It is found that DP results from FRET are consistent with other established measurement methods, such as nuclear magnetic resonance (NMR) spectroscopy. Altogether, this work presents a broadly applicable and straightforward method to in situ characterize Ree of low molecular weight oligomers and their DP during reaction.