Tandem Integration of Biological and Electrochemical Catalysis for Efficient Polyester Upcycling under Ambient Conditions.

Excessive production of waste polyethylene terephthalate (PET) poses an ecological challenge, which necessitates developing technologies to extract the values from end-of-life PET. Upcycling has proven effective in addressing the low profitability of current recycling strategies, yet existing upcycling technologies operate under energy-intensive conditions. Here we report a cascade strategy to steer the transformation of PET waste into glycolate in an overall yield of 92.6% under ambient conditions. The cascade approach involves setting up a robust hydrolase with 95.6% PET depolymerization into ethylene glycol (EG) monomer within 12 h, followed by an electrochemical process initiated by a CO-tolerant Pd/Ni(OH)2 catalyst to convert the EG intermediate into glycolate with high Faradaic efficiency of 97.5%. Techno-economic analysis and life cycle assessment indicate that, compared with the widely adopted electrochemical technology that heavily relies on alkaline pretreatment for PET depolymerization, our designed enzymatic-electrochemical approach offers a cost-effective and low-carbon pathway to upgrade PET.

Unraveling the Impact of Oxygen Vacancy on Electrochemical Valorization of Polyester Over Spinel Oxides.

Electrochemical upcycling of end-of-life polyethylene terephthalate (PET) using renewable electricity offers a route to generate valuable chemicals while processing plastic wastes. However, it remains a huge challenge to design an electrocatalyst with reliable structure-property relationships for PET valorization. Herein, spinel Co3O4 with rich oxygen vacancies for improved activity toward formic acid (FA) production from PET hydrolysate is reported. Experimental investigations combined with theoretical calculations reveal that incorporation of VO into Co3O4 not only promotes the generation of reactive hydroxyl species (OH*) species at adjacent tetrahedral Co2+ (Co2+ Td), but also induces an electronic structure transition from octahedral Co3+ (Co3+ Oh) to octahedral Co2+ (Co2+ Oh), which typically functions as highly-active catalytic sites for ethylene glycol (EG) chemisorption. Moreover, the enlarged Co-O covalency induced by VO facilitates the electron transfer from EG* to OH* via Co2+ Oh-O-Co2+ Td interaction and the following C─C bond cleavage via direct oxidation with a glyoxal intermediate pathway. As a result, the VO-Co3O4 catalyst exhibits a high half-cell activity for EG oxidation, with a Faradaic efficiency (91%) and productivity (1.02 mmol cm-2 h-1) of FA. Lastly, it is demonstrated that hundred gram-scale formate crystals can be produced from the real-world PET bottles via two-electrode electroreforming, with a yield of 82%.

Recent advances on solar-driven valorization of polyethylene terephthalate plastics into value-added chemicals.

The random disposal and immature recycling of post-consumer polyethylene terephthalate (PET) packages lead to a severe threaten to the ecological system owing to slow natural degradation kinetics of PET plastic, and meanwhile cause a waste of carbon resources stored in PET plastics. Many methods have been developed to recycle PET plastics, such as mechanical recycling, which induces a reduced quality relative to the virgin PET. In recent years, the photocatalytic conversion of PET plastic wastes into chemicals has received considerable attention due to their unique advantages, including mild conditions, less energy consumption, and simple operation. In this review, we have summarized the latest achievements in photoreforming of PET plastics into value-added chemicals. Primarily, we described the mechanism for bond cleavage during PET photoreforming, the emerging pretreatment methodologies for PET plastics, and the advantages of photocatalytic PET plastics conversion. Then, we introduced electro-/bio-assisted photocatalysis technologies for PET disposal and commented their strengths and limitations. Finally, we put forward the challenges and potential advances in the domain of photocatalytic PET plastics conversion.

Plant growth-promoting and antibacterial activities of cultivable bacteria alive in tobacco field against Ralstonia solanacearum.

Bacterial wilt disease caused by Ralstonia solanacearum leads to decrease of crops yield. Investigation of cultivable bacteria diversity provides more microbial species for screening antagonistic bacteria. In the present study, a variety of cultivation methods were used to investigate the diversity of cultivable bacteria alive in tobacco field. A total of 441 bacterial strains were obtained that belonged to four phyla, 49 genera and 146 species. Actinobacteria and Proteobacteria were the dominant phyla. Agrobacterium, Arthrobacter, Bacillus, Klebsiella, Paenarthrobacter, Pseudomonas and Pseudarthrobacter were the dominant genera. Some rare genera were discovered including Bosea, Cedecea, Delftia and Dyella. Diversity, species and abundances of bacteria altered under different cultivation conditions. One hundred three bacterial strains showed plant growth-promoting attributes. Twenty Bacillus strains showed high antibacterial activity against R. solanacearum. In field experiments, individual strain and consortia of Bacillus subtilis, B. siamensis and B. vallismortis effectively inhibited bacterial wilt. The core genes that controlled synthesis of secondary metabolites were knocked out in B. vallismortis SSB-10. Difficidin, which was synthesized by dif operon and controlled by sfp gene, was the antibacterial substance produced by SSB-10. Difficidin destroyed cell wall and cell membrane of R. solanacearum and inhibited its motility, production of extracellular polysaccharides and cellulase activity.

The influencing factors and functions of DNA G-quadruplexes.

G-quadruplexes form folded structures because of tandem repeats of guanine sequences in DNA or RNA. They adopt a variety of conformations, depending on many factors, including the type of loops and cations, the nucleotide strand number, and the main strand polarity of the G-quadruplex. Meanwhile, the different conformations of G-quadruplexes have certain influences on their biological functions, such as the inhibition of transcription, translation, and DNA replication. In addition, G-quadruplex binding proteins also affect the structure and function of G-quadruplexes. Some chemically synthesized G-quadruplex sequences have been shown to have biological activities. For example, bimolecular G-quadruplexes of AS1411 act as targets of exogenous drugs that inhibit the proliferation of malignant tumours. G-quadruplexes are also used as vehicles to deliver nanoparticles. Thus, it is important to identify the factors that influence G-quadruplex structures and maintain the stability of G-quadruplexes. Herein, we mainly discuss the factors influencing G-quadruplexes and the synthetic G-quadruplex, AS1411. SIGNIFICANCE OF THE STUDY: This review summarizes the factors that influence G-quadruplexes and the functions of the synthetic G-quadruplex, AS1411. It also discusses the use of G-quadruplexes for drug delivery in tumour therapy.

Development and evaluation of nomograms and risk stratification systems to predict the overall survival and cancer-specific survival of patients with hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, and patients with HCC have a poor prognosis and low survival rates. Establishing a prognostic nomogram is important for predicting the survival of patients with HCC, as it helps to improve the patient's prognosis. This study aimed to develop and evaluate nomograms and risk stratification to predict overall survival (OS) and cancer-specific survival (CSS) in HCC patients. Data from 10,302 patients with initially diagnosed HCC were extracted from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2017. Patients were randomly divided into the training and validation set. Kaplan-Meier survival, LASSO regression, and Cox regression analysis were conducted to select the predictors of OS. Competing risk analysis, LASSO regression, and Cox regression analysis were conducted to select the predictors of CSS. The validation of the nomograms was performed using the concordance index (C-index), the Akaike information criterion (AIC), the Bayesian information criterion (BIC), Net Reclassification Index (NRI), Discrimination Improvement (IDI), the receiver operating characteristic (ROC) curve, calibration curves, and decision curve analyses (DCAs). The results indicated that factors including age, grade, T stage, N stage, M stage, surgery, surgery to lymph node (LN), Alpha-Fetal Protein (AFP), and tumor size were independent predictors of OS, whereas grade, T stage, surgery, AFP, tumor size, and distant lymph node metastasis were independent predictors of CSS. Based on these factors, predictive models were built and virtualized by nomograms. The C-index for predicting 1-, 3-, and 5-year OS were 0.788, 0.792, and 0.790. The C-index for predicting 1-, 3-, and 5-year CSS were 0.803, 0.808, and 0.806. AIC, BIC, NRI, and IDI suggested that nomograms had an excellent predictive performance with no significant overfitting. The calibration curves showed good consistency of OS and CSS between the actual observation and nomograms prediction, and the DCA showed great clinical usefulness of the nomograms. The risk stratification of OS and CSS was built that could perfectly classify HCC patients into three risk groups. Our study developed nomograms and a corresponding risk stratification system predicting the OS and CSS of HCC patients. These tools can assist in patient counseling and guiding treatment decision making.

Diagenetic Genesis and Evolution of Coal-Bearing Tight Sandstone Reservoir in the Yangxia Formation, Northern Kuqa Depression, Tarim Basin.

Coal seams of the Yangxia Formation are widespread in the northern part of the Kuqa Depression in the Tarim Basin. During the thermal evolution of the coal seams, the generated fluids of different periods and natures have a significant impact on tight sandstone reservoirs. To further investigate the diagenetic characteristics and reservoir genesis of the tight sandstones due to the influence of coal seams, an in-depth exploration of the causes of dissolution and cementation in the reservoirs was conducted through thin-section casting, cathode luminescence, scanning electron microscopy, carbon-oxygen isotopic analyses, and X-ray diffraction of whole rock and authigenic clay minerals, along with burial evolution history and fluid evolution history. It is suggested that two phases of acidic fluids are mainly produced during the thermal evolution process of coal seams, including an early humic acid and a late organic carboxylic acid. The early phase humic acid plays a purifying role in reservoirs with coarse particles, rigidity-rich particles, and good permeability conditions. It selectively dissolves sedimentary calcareous mud and calcite, and the dissolution products are completely migrated. At the same time, it inhibits early carbonate cementation. The late organic carboxylic acid will dissolve potassium feldspar and some volcanic rock debris, and the dissolution products are difficult to migrate under the sealing conditions caused by lithological differences, which often take the cementation form of siliceous overgrowth and kaolinite or illite. In addition to the cementation resulting from the dissolution products of acidic fluids produced by the coal seams, the CO2-rich fluids generated by the coal seam thermal evolution will combine with ions such as Ca2+ from different sources, resulting in two phases of carbonate cementation. Based on the above research, this study summarizes a set of diagenetic evolution models for coal-bearing reservoirs.

Efficacy and safety of GST-HG171 in adult patients with mild to moderate COVID-19: a randomised, double-blind, placebo-controlled phase 2/3 trial.

Background: GST-HG171 is a potent, broad-spectrum, orally bioavailable small-molecule 3C like protease inhibitor that has demonstrated greater potency and efficacy compared to Nirmatrelvir in pre-clinical studies. We aimed to evaluate the efficacy and safety of orally administered GST-HG171 plus Ritonavir in patients with coronavirus disease 2019 (COVID-19) infected with emerging XBB and non-XBB variants. Methods: This randomised, double-blind, placebo-controlled phase 2/3 trial was conducted in 47 sites in China among adult patients with mild-to-moderate COVID-19 with symptoms onset ≤72 h. Eligible patients were randomised 1:1 to receive GST-HG171 (150 mg) plus Ritonavir (100 mg) or corresponding placebo tablets twice daily for 5 days, with stratification factors including the risk level of disease progression and vaccination status. The primary efficacy endpoint was time to sustained recovery of clinical symptoms within 28 days, defined as a score of 0 for 11 COVID-19-related target symptoms for 2 consecutive days, assessed in the modified intention-to-treat (mITT) population. This trial was registered at ClinicalTrials.gov (NCT05656443) and Chinese Clinical Trial Registry (ChiCTR2200067088). Findings: Between Dec 19, 2022, and May 4, 2023, 1525 patients were screened. Among 1246 patients who underwent randomisation, most completed basic (21.2%) or booster (74.9%) COVID-19 immunization, and most had a low risk of disease progression at baseline. 610 of 617 who received GST-HG171 plus Ritonavir and 603 of 610 who received placebo were included in the mITT population. Patients who received GST-HG171 plus Ritonavir showed shortened median time to sustained recovery of clinical symptoms compared to the placebo group (13.0 days [95.45% confidence interval 12.0-15.0] vs. 15.0 days [14.0-15.0], P = 0.031). Consistent results were observed in both SARS-CoV-2 XBB (45.7%, 481/1053 of mITT population) and non-XBB variants (54.3%, 572/1053 of mITT population) subgroups. Incidence of adverse events was similar in the GST-HG171 plus Ritonavir (320/617, 51.9%) and placebo group (298/610, 48.9%). The most common adverse events in both placebo and treatment groups were hypertriglyceridaemia (10.0% vs. 14.7%). No deaths occurred. Interpretation: Treatment with GST-HG171 plus Ritonavir has demonstrated benefits in symptom recovery and viral clearance among low-risk vaccinated adult patients with COVID-19, without apparent safety concerns. As most patients were treated within 2 days after symptom onset in our study, confirming the potential benefits of symptom recovery for patients with a longer duration between symptom onset and treatment initiation will require real-world studies. Funding: Fujian Akeylink Biotechnology Co., Ltd.

Symmetry or asymmetry: which one is the platform of nitrogen vacancies for alkaline hydrogen evolution.

Conventional nitrogen vacancies with a symmetric coordination of metal cations (i.e., M1-Nv-M1) play a crucial role in tuning the local environment of the metal sites in metal nitrides and improving their electrochemical activity in the hydrogen evolution reaction (HER). However, the symmetric Nv sites, which feature a uniform charge distribution on adjacent metal sites, suffer from sluggish water dissociation kinetics and a poor capability for hydrogen desorption. Here, we fabricated Cr-doped and Nv-rich Co4N nanorods grown on a Ni foam (Cr-Co4N-Nv/NF) with asymmetric Cr-Nv-Co sites to effectively catalyze hydrogen evolution under alkaline conditions, with a low overpotential of 33 mV at a current density of 10 mA cm-2 and a small Tafel slope of 37 mV dec-1. The experimental characterizations and theoretical simulations collectively reveal that the construction of asymmetric Cr-Nv-Co sites gives rise to the upshift of the d-band center, thus promoting water adsorption and activation. Moreover, asymmetric Nv sites allow a balance between hydrogen adsorption and desorption, which avoids the limited desorption process over the symmetric Co-Nv-Co sites.

Inactivated SARS-CoV-2 booster vaccine enhanced immune responses in patients with chronic liver diseases.

Chronic liver disease (CLD) entails elevated risk of COVID-19 severity and mortality. The effectiveness of the booster dose of inactivated SARS-CoV-2 vaccine in stimulating antibody response in CLD patients is unclear. Therefore, we conducted a cross-sectional study involving 237 adult CLD patients and 170 healthy controls (HC) to analyze neutralizing antibodies (NAbs) against SARS-CoV-2 prototype and BA.4/5 variant, anti-receptor binding domain (RBD) IgG, and total anti-SARS-CoV-2 antibodies. Serum levels of the total anti-SARS-CoV-2 antibodies, anti-RBD IgG and inhibition efficacy of NAbs were significantly elevated in CLD patients after the booster dose compared with the pre-booster dose, but were relatively lower than those of HCs. Induced humoral responses decreased over time after booster vaccination. The neutralization efficiency of the serum against BA.4/5 increased but remained below the inhibition threshold. All four SARS-CoV-2 antibodies, including total anti-SARS-CoV-2 antibodies, anti-RBD IgG and NAbs against prototype and BA.4/5, were lower in patients with severe CLD than those with non-severe CLD. After booster shot, age and time after the last vaccine were the risk factors for seropositivity of NAb against BA.4/5 in CLD patients. Additionally, white blood cell counts and hepatitis B core antibodies were the protective factors, and severe liver disease was the risk factor associated with seropositivity of total anti-SARS-CoV-2 antibodies. Overall, our data uncovered that antibody responses were improved in CLD patients and peaked at 120 days after the booster vaccines. All antibodies excepting total anti-SARS-CoV-2 antibodies declined after peak. CLD patients exhibited impaired immunologic responses to vaccination and weakened NAbs against BA.4/5, which hindered the protective effect of the booster shot against Omicron prevalence. Cellular immune responses should be further evaluated to determine the optimal vaccine regimen for CLD patients.

SARS-CoV-2 Vaccine Uptake among Patients with Chronic Liver Disease: A Cross-Sectional Analysis in Hebei Province, China.

Chronic liver disease (CLD) patients have higher mortality and hospitalization rates after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study aimed to explore SARS-CoV-2 vaccine perceptions, side effects, factors associated with nonvaccination and attitudes toward fourth-dose vaccine among CLD patients. The differences between vaccinated and unvaccinated groups among 1491 CLD patients and the risk factors associated with nonvaccination status were analyzed. In total, 1239 CLD patients were immunized against SARS-CoV-2. CLD patients have a high level of trust in the government and clinicians and were likely to follow their recommendations for vaccination. Reasons reported for nonvaccination were mainly concerns about the vaccines affecting their ongoing treatments and the fear of adverse events. However, only 4.84% of patients reported mild side effects. Risk factors influencing nonvaccination included being older in age, having cirrhosis, receiving treatments, having no knowledge of SARS-CoV-2 vaccine considerations and not receiving doctors' positive advice on vaccination. Furthermore, 20.6% of completely vaccinated participants refused the fourth dose because they were concerned about side effects and believed that the complete vaccine was sufficiently protective. Our study proved that SARS-CoV-2 vaccines were safe for CLD patients. Our findings suggest that governments and health workers should provide more SARS-CoV-2 vaccination information and customize strategies to improve vaccination coverage and enhance vaccine protection among the CLD population.

The miR-23b/27b/24-1 Cluster Inhibits Hepatic Fibrosis by Inactivating Hepatic Stellate Cells.

BACKGROUND & AIMS: Hepatic fibrosis is characterized by hepatic stellate cell (HSC) activation and transdifferentiation-mediated extracellular matrix (ECM) deposition, which both contribute to cirrhosis. However, no antifibrotic regimen is available in the clinic. microRNA-23b/27b/24-1 cluster inhibition of transforming growth factor-ß (TGF-ß) signaling during hepatic development prompted us to explore whether this cluster inhibits HSC activation and hepatic fibrosis. METHODS: Experimental fibrosis was studied in carbon tetrachloride (CCl4)-treated C57BL/6 mice. After administration of miR-23b/27b/24-1 lentivirus or vehicle, animals were euthanized for liver histology. In primary rat HSC and HSC-T6, the anti-fibrotic effect of miR-23b/27b/24-1 cluster was furtherly investigated by RNA-sequencing, luciferase reporter assay, western blotting and bioinformatic means. RESULTS: In this study, we showed that increasing the miR-23b/27b/24-1 level through intravenous delivery of miR-23b/27b/24-1 lentivirus ameliorated mouse hepatic fibrosis. Mechanistically, the miR-23b/27b/24-1 cluster directly targeted messenger RNAs, which reduced the protein expression of 5 secretory profibrotic genes (TGF-ß2, Gremlin1, LOX, Itgα2, and Itgα5) in HSCs. Suppression of the TGF-ß signaling pathway by down-regulation of TGF-ß2, Itgα2, and Itgα5, and activation of the bone morphogenetic protein signaling pathway by inhibition of Gremlin1, decreased extracellular matrix secretion of HSCs. Furthermore, down-regulation of LOX expression softened the ECM. Moreover, a reduction in tissue inhibitors of metalloproteinase 1 expression owing to weakened TGF-ß signaling increased ECM degradation. CONCLUSIONS: Hepatic overexpression of the miR-23b/27b/24-1 cluster blocked hepatic fibrosis and may be a novel therapeutic regimen for patients with hepatic fibrosis.

Differential characterization of stress sensitivity and its main control mechanism in deep pore-fracture clastic reservoirs.

Stress sensitivity in reservoirs is critical during the exploitation of oil and gas fields. As a deep clastic reservoir under strong tectonic compression, the Ahe Formation in the northern tectonic zone of the Kuqa depression exhibited strong stress sensitivity effect. However, the conventional evaluation method by using permeability damage rate as a constraint restricts the mechanistic understanding of the strong stress sensitivity effect. In this study, morphology of stress sensitivity test curve, coupled with rate change of permeability and extent of irreversible damage in actual sample measurement through micro-CT in-situ scanning, is used to characterize differentially. The strong stress sensitivity effects of the studied intervals can be divided into three types: (1) rapid change in permeability-weak irreversible damage, (2) moderate change in permeability-strong irreversible damage and (3) moderate change in permeability-moderate irreversible damage. The strong stress sensitivity is caused by the micro-pores and micro-fractures, which are widely developed in the studied reservoir. The mechanisms caused by the two types of pore are different. The stress sensitivity effects in micro-fracture-rich reservoirs are characterized by rapid change in permeability and weak irreversible damage. Meanwhile, the stress sensitivity effects in micro-pore-rich reservoirs are manifested as moderate change in permeability and strong irreversible damage. The study shows that the differences in the content of micro-pores and micro-fractures and their reverse mechanisms of stress sensitivity co-create different types of stress sensitivity within the samples. Accordingly, the differences of the stress sensitivity type in macroscopic samples are caused by the competition between the microscopic differences of pore types.

Highly Conductive, Flexible, and Nonflammable Double-Network Poly(ionic liquid)-Based Ionogel Electrolyte for Flexible Lithium-Ion Batteries.

The solid-state lithium-ion battery is proposed as the ultimate form of battery and has rapidly become an updated attentive research field due to its high safety and extreme temperature tolerance. However, current solid-state electrolytes hardly meet the requirement in practical applications due to its low ionic conductivity, weak mechanical properties, and poor interfacial contact between the electrolyte and the electrode. In this work, we developed a double-network-supported poly(ionic liquid)-based ionogel electrolyte (DN-Ionogel) via a one-step method. Due to its compact cross-linking structure, the leakage-free DN-Ionogel electrolyte exhibits outstanding flexibility and favorable mechanical properties. In this ionogel electrolyte, the double network favors dissociation of lithium bis(trifluoromethanesulfony)imide (LiTFSI), further resulting in remarkable ionic conductivity (1.8 × 10-3 S/cm, room temperature), wide electrochemical window (up to 5.0 V), and high lithium-ion transference number (0.33). Furthermore, the cell (LiFePO4||DN-Ionogel||Lithium) delivers a discharge capacity as high as 150.5 mAh/g, stable cyclic performance (over 200 cycles), and superior rate behavior.

Boron and nitrogen co-doped double-layered mesopore-rich hollow carbon microspheres as high-performance electrodes for supercapacitors.

In this paper, double-layered mesopore-rich hollow carbon microspheres (DHCM) were prepared by a Stöber method using tetraethyl orthosilicate, resorcinol and formaldehyde as precursor materials, and further utilized as carbon sources to prepare the boron and nitrogen co-doped double-layered mesopore-rich hollow carbon microspheres (B, N-DHCM) by hydrothermal approach utilizing ammonium tetraborate tetrahydrate (NH4B5O8·4H2O) as boron and nitrogen sources. Compared with the undoped DHCM, the as-obtained B, N-DHCM displays improved capacitive properties with a high specific capacitance (221.5 F g-1 at 1 A g-1), good rate performance (104.1 F g-1 at 20 A g-1) and superior cycle life (91% of capacitance retention at 3 A g-1 after 10,000 cycles). The outstanding capacitive performances result from the synergistic effect of the unique double-layered mesopore-rich hollow structure contributing to the rate property and cycle stability and the modification of B and N co-doping providing pseudocapacitance for the enhancement of specific capacitance. Therefore, the excellent capacitive behaviors render the B, N-DHCM promising electrode materials for application in supercapacitors and other energy storage systems.

An exploration of aptamer internalization mechanisms and their applications in drug delivery.

INTRODUCTION: As 'chemical antibodies', aptamers have some advantages, such as lack of immunogenicity, rapid tissue penetration, cell internalization and so on. Consequently, more and more aptamers have been screened out by the systematic evolution of ligands through exponential enrichment for the desired cells or membrane receptors. On the basis of the result, researchers use aptamers to guide drug targeting to the desired cells and internalization in vivo. AREAS COVERED: In this review, we explore the mechanisms of cargo- or aptamer-mediated internalization, and then briefly summarize five strategies for exploring the mechanism of aptamer internalization. Finally, we focus on four types of applications involving aptamer internalization: aptamers as drugs, aptamers as chemical drug-delivery systems, aptamer-based chimeras and aptamer-conjugated nanoparticles or block copolymer micelles. EXPERT OPINION: Two aptamer-internalization mechanisms are known, namely receptor-mediated endocytosis and macropinocytosis. The latter mechanism, which is has only been verified in the internalization of nucleolin aptamer shuttles between the nucleus and cytoplasm, may be important for nuclear internalization and cargo molecule escape from the endosomal compartment. Thus, it is feasible to use some strategies to further explore the macropinocytosis internalization mechanism and then to screen for aptamers similar to the nucleolin aptamer for use with the desired cell types as a targeted delivery tool.

Photochemical-controlled switching based on azobenzene monolayer modified silicon (111) surface.

Azobenzene-containing compounds were covalently attached onto Si(111) surfaces via Si-O linkages using a two-step procedure. The modified Si(111) surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy measurements. The monolayer surface showed preferably chemical stability. Switchable photoisomerizability of azobenzene molecules on these modified surfaces was observed in response to alternating UV and visible light exposure. The measured conductivity showed distinct difference with trans and cis forms of azobenzene compounds on as-modified Si(111) surfaces.